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AVIAN INFLUENZA
April 17, 2009.
Jennifer Thomsen, Jennifer Bodily, Keith Bell , Dan Delonas,
Jamie Garrett and Jenny Ge.
INTRODUCTION AND REVIEW
Avian influenza, more commonly known as the bird flu, is an orthomyxovirus
that, although currently affects humans on a small level, is believed to be capable of causing the next pandemic. There are three types of Influenza viruses (A, B, and C); Type A is primarily in fowl, type B primarily affects humans, and type C affects humans and swine. Type A is known for its different subtypes and strains; the subtype of concern worldwide is H5N1 based on its surface glycoproteins hemagglutinin (H or HA) and neuramidase (N or NA)21. This virus is carried passively in the intestinal tracts of wild waterfowl and can be transmitted to humans via a mammalian intermediate (i.e. swine); however transmission from bird to human is evolving. The commonly used antiviral agents for influenza have been shown ineffective against H5N1; however other antiviral agents show promising effects18. As of March 30, 2009 256 humans worldwide have died from infection of the H5N1 virus14. Worldwide, organizations and agencies such as the World Health Organization (WHO) and the Center for Disease Control and Prevention (CDC) have been researching ways to prepare for the next predicted pandemic.
- History of Avian Influenza
- Current Statistics
- Serotyping nomenclature H5N1
- Viral Evolution and Structure of H5N1
- RESEARCH
- References
From its earliest human appearance in 1997 until its newest form today the history of bird flu has been evolving each day. This strain of the flu differs from past influenza viruses that have caused outbreaks due to the fact that its spread is quick and difficult to contain16. The bird flu virus is a strain of the influenza A virus which is a RNA negative sense >virus so it is prone to mistakes in its replication process. Due to its characteristics this virus has been classified as an orthomyxovirus. The bird flu virus was primarily spread through wild birds, and was able to spread to farms quickly because of the lifestyle of these wild birds. Usually influenza viruses are species specific meaning that the virus rarely transmits from one species to another. There are hundreds of strains of bird flu viruses; since 1997 four have emerged that demonstrate the ability to cause human infection: H5N1, H7N3, H7N7, and H9N2. Of these H5N1 is the strain that is most pathogenic causing disease and death. The other strains usually only display mild symptoms. H5N1, is, at present time, of most concern because it has caused the most cases of disease and death in humans, and it has the potential to mutate and cause the next pandemic15.
- 1997 1st known case of bird flu appeared in Hong Kong. The H5N1 virus was discovered as being transmitted from birds to humans and rarely from person to person16.
- 1999 H9N2 form of the virus infected two children, and during this same time a few more cases of this same form of virus was discovered in China16.
- >2003 people in Hong Kong who had just returned from China were infected with H5N116.
- The Netherlands had an outbreak of H7N7.
- Hong Kong was hit with another case of a H9N2 strain.
- Vietnamese confirmed H5N1 as the highly pathogenic strain of the influenza virus.
- 2003 with more outbreaks in Asia laboratories have discovered that H5N1 has mutated from its earliest form in 1997, and is resistant to certain M2 inhibiting antiviral drugs like Amantadine and Rimantadine16.
- 2004 Texas reported the presence of H5N2 found in poultry, but action was taken and the spread of this strain was prevented16.
- 2005 WHO reports 122 human cases so far with 62 of those people dying from the H5N1 virus16.
- 2005 Plans are made to develop a vaccine for the H5N1 virus16.
Potential for Pandemics/Endemics
A pandemic can occur when three conditions are met: a new disease emerges, it is capable of infecting and causing serious illness in humans, and it spreads easily and sustainably between humans. The H5N1 virus currently meets two of these conditions. It is an emerging disease and it is capable of infecting and causing serious illness in humans. Fortunately, the virus has not yet demonstrated the propensity to spread easily and sustainably between humans.22
Avian influenza viruses acquire the ability to sustainably transmit between humans by two primary mechanisms. The first is reassortment where a human or intermediate host is coinfected with avian and human strains of a virus and these viruses reassemble their genetic material into a third strain containing characteristics of both viruses.23,24 The Asian and Hong Kong influenza strains arose as a result of genetic reassortment within a porcine intermediate.24
The second mechanism is mutation where an influenza strain mutates on its own without interacting with another strain. Molecular analysis indicates that the H1N1 strain that caused the Spanish Influenza pandemic arose from genetic mutation and was originally a purely avian virus .24
Numbers
The WHO releases regular fact sheets containing the most recently reported data concerning the current H5N1 situation. To date (March 2009), there have been more than 400 confirmed human cases worldwide and more than 250 deaths. No human or animal cases have been reported in the western hemisphere.25
Inferences can be made based upon the statistical data collected from previous pandemics when analyzing the potential severity of a future pandemic. In the 20th century, there were three major influenza pandemics: the Spanish Influenza of 1918-1920, the Asian Flu of 1957-1958, and the Hong Kong Flu of 1968-1969. Of these, the Spanish Influenza was the most severe causing an estimated 500 million infections and between 50 and 100 million deaths. The CDC estimates that another influenza strain equal in pathogenicity to the Spanish Influenza could cause, even with the improvements in health care since 1920, greater than 100 million deaths. Scientific, statistical, and clinical data collected since 1997 indicate that the H5N1 strain is potentially more pathogenic than the H1N1 strain that caused the Spanish Influenza.23
The WHO and CDC both have monitoring programs in place to track the current H5N1 situation.26 The main difference between the WHO response stages and federal response stages is that the WHO concerns itself with worldwide events whereas the federal response focuses primarily upon events within the United States. In 2007 the CDC implemented the Pandemic Severity Index to assess the severity of an actual pandemic and also to determine what a prudent response to the outbreak might be.27
Potential for spread to the USA
In 2005, articles were published in Nature and Science indicating it might be possible to contain an emerging influenza pandemic at its source. Both published articles use data from the 2000 Thai census as well as a statistical measure called the basic reproduction number (R0). The articles conclude that a combination of targeted antiviral prophylaxis, social distancing measures, and pre-vaccination would be most desirable to achieve this effect.28,29
Ira M. Longini Jr. et al. reported to Nature that targeted antiviral prophylaxis could contain an emerging strain if R0 < 1.6. Their statistical models further indicate that prophylaxis combined with quarantine and pre-vaccination could potentially handle an emerging strain with an R0 as high as 2.4. The results reported in the article indicate that pre-vaccination would be desirable in efforts to contain emerging influenza strains.28
In 2007, the United States Food and Drug Administration (FDA) approved a vaccine against H5 strains. The vaccine is part of the national stockpile, but will otherwise be unavailable.30 Efforts are ongoing to produce large quantities of a fully immunogenic vaccine against H5 strains of influenza and an article published in 2008 in the New England Journal of Medicine explains several of the challenges encountered in efforts to mass-produce such a vaccine. The 2007 vaccine is questioned in this article because a relatively high dosage (two 90 microliter doses of HA) was required to achieve an acceptable titer in >50% of those vaccinated in clinical trials. Additionally, there is the risk that a vaccine made in preparation for a pandemic might not provide immunity to the strain that eventually emerges.31
Both 2005 articles acknowledge the prospect of containing a pandemic at the source to be problematic. Neil M. Ferguson et al. indicate that several criteria must be met for this to succeed including: rapidly identifying the original case cluster, rapid identification of and delivery of treatment to target groups, effective delivery to >90% of the target groups, sufficient stockpiles of drug, cooperation with the containment strategies, and international cooperation in policy development. They also acknowledge that Thailand (the country modeled in the studies) is one of the best prepared countries in southeast Asia to handle such an outbreak, and that other countries require substantial improvements in healthcare to implement such a strategy.29 Longini et al. also emphasize the need for quick delivery of prophylactic medications.28
In 2004 the United States Department of Agriculture (USDA) issued an import ban on poultry from countries with reported cases of avian influenza viruses.32,33 The USDA import ban makes it unlikely that an H5N1 pandemic would originate in the United States. However the articles published in 2005 indicate that containment of an initial outbreak overseas, while possible, could still prove quite difficult.
In 2006 another research team led by Neil M. Ferguson published a second article in Nature discussing strategies for mitigating a pandemic should initial containment methods fail. The United States and Great Britain were used in these models for this study. These studies determined that travel restrictions would not delay spread by more than three weeks unless 99% effective and focus on methods for control should a pandemic reach a developed country such as the United States or Great Britain. The researchers further emphasize that the best strategy for mitigating a pandemic would be a combination of measures including school closures, travel restrictions, rapid recognition and treatment of symptoms (within 24 hours of initial symptoms,) stockpiled vaccines, and enough anti-viral drugs for 50% of the population.34
SEROTYPING NOMENCLATURE FOR H5N1
The outbreaks that have occured have been found to be caused by the the H5 and H7 subtypes of the virus. These highly pathogenic forms of the bird flu have a distinct set of basic amino acids that distinguishes them from other forms of avian flu viruses. Not every strain of H5 and H7 are highly pathogenic but these strains do have to potential to become highly pathogenic15.
The avian influenza viruses are categorized into subtypes based on the serological typing of the viruses two surface glycoproteins (HA and NA). Currently, there are 16 HA and 9 NA that have been identified.20 All of these have been detected and currently circulate in the wild avian reservoirs.21
VIRAL EVOLUTION AND STRUCTURE OF H5N1
Viral Structure
The structure of Influenza A virus as depicted is representative of a virion whose diameter is roughly 120 nm with a genome composed of eight helical nucleocapsid segments which come to approximately 13,600 nucleotides of negative-sense RNA. 19 These eight different gene segments encode at least 10 distinct viral proteins. The structural proteins are hemagglutinin (HA), neuraminidase (NA), and membrane ion channel (M2). The internal proteins are matrix protein (M1) and nucleoprotein (NP). The RNA polymerization complex is composed of polymerase basic protein 1 (PB1), polymerase basic protein 2 (PB2) and polymerase acidic protein (PA). The non-structural proteins are (NS1) and (NS2); collectively known as nuclear export protein (NEP). 20
Viral Component Roles
Protein HA is involved in viral attachment to host cell, entry, and evading host immunologic response. Protein NA is involved in release of mature virions, thus completing an effective infection. Proteins PB1, PB2, PA, and NP are all involved in transcription and replication of the virus.21 Protein M1 establishes a connection from the viral RNA to the lipid membrane. M2 is an integral membrane protein that acts as a channel for hydrogen ion passage necessary for removal of viral coat.20 NS proteins, albeit not produced in the virus, but rather in the host, play a role in allowing viral mRNA to leave the hosts' nucleus.19
Viral Replication
Influenza A virus, like other viruses, requires a host for growth and viral propagation. Thus, cellular proteins from the host are often commandeered by the virus. Some examples of such are the cellular mRNA cap and intramolecular splicing machinery of the host.19 >However, in order to achieve an effective infection, multiple tasks must be accomplished. Initially, the viral HAs attach to the host cell receptor: sialic acid. The virus is endocytosed and the endosome becomes acidic due to M2 protein allowing hydrogen ions into the virion. Due to the lowered pH, a conformational change of the HA protein can ensue which allows the fusion domain to become active. This activity allows the viral membrane and the endosomal membrane to fuse, resulting in the release of the viral RNA-polymerase complex into the host cytoplasm. This complex is actively guided to the nucleus via the nuclear localization of the viral NP protein. As the negative-sense viral RNA reaches the nucleus, polymerase subunits begin making positive-sense and template RNA. Notably, the majority of the viral genetic information is geared toward these events, with the polymerase subunits taking roughly 50% of the genetic information.20 The polymerase subunits PB1 and PB2 need to be active for viral mRNA synthesis (positive-sense RNA). The PB1 subunit will bind the conserved 3' and 5' sequence of the viral RNA with its active sites and also cleave the cellular mRNA cap. The reason why the virus has to take the hosts mRNA cap is because it cannot cap its own mRNA. Thus, the beginning of viral mRNA has host mRNA with a 5' methylated cap. To continue supplying these caps for incorporation, the RNA polymerization complex will actively transcribe the host mRNA, but will inhibit their transport and synthesis of cellular protein.19 The PB2 is the subunit that has the capability of binding the host mRNA to itself for polymerization to ensue. Polymerization by PB1 of the viral RNA will stop short of the 5' end where a U region is located. This U region will cause the polymerization to "stutter" causing a poly-A tail to form.19 Another host function utilized by the virus is the intramolecular splicing capability of the nucleus. Two of the helical nucleocapsid segments incorporated into the nucleus have mRNA precursors that are able to be spliced. This results in the generation of 10 distinct mRNAs encoded by eight nucleocapsid segments.19 Synthesis of viral mRNA will continue until multiple copies of the viral proteins NP and PA are formed which will cause a switch to synthesizing full length template RNA. However, this mechanism is not completely understood.19 When new viral RNA is synthesized, it is exported out of the nucleus by viral proteins M1 and NS2. The NS2 protein has an export signal that is able to bind to the nuclear export protein. Once the viral mRNA is exported from the nucleus, it can be translated on the rough endoplasmic reticulum and processed in the golgi apparatus and then these proteins will help modify the host cell membrane for eventual budding of the virus. Those proteins that are associated with the nucleocapsid segments migrate to the nucleus where they essentially do the reverse by helping synthesize negative-sense genomic RNA from positive-sense template. Once nucleocapsid segments are generated, they associate with the modified cell membrane and become encapsulated in vesicles which then bud off of the host.19 In order for these viral particles to bud without self-binding or aggregation to the host cell, the viral protein NA must remove sialic acid from the surface glycoproteins.20 However, the vast majority of these viral particles (90%) are non-infectious due to inefficient packaging of the RNA. Nonetheless, this ineffective packaging may result in a virus that has altered abilities. For example, multiple NS genes incorporated has lead to the hypothesis of increased resistance to interferon.20
Viral Virulence
The matter of what makes the virus virulent is not an “open and closed” case, but rather a number of characteristics of the virus, selective pressures, host factors and many other likely components that could yet again reveal the destructive form of 1918 pandemic.
The virus has characteristics which enable diversity among viral populations. Foremost, the virus is an RNA virus and they have the highest mutation rate known in nature due to the RNA polymerization complex not having an error correction system incorporated within. One mutation occurs per genomic replication!21 This results in what is called a quasi-species population.20 This population is subjected to the selective pressures of not only the host, but of the varied viral population itself.21 Such an environment creates conditions that favor genetic changes. It has been shown that a single amino acid change from Glutamic acid (E) to Lysine (K) at the amino acid position 627 of the polymerase protein PB-2, results in a marked increase in virulence and adaptability to mammalian hosts.20 In addition, the inaccurate replication ties in with the packaging of the virus prior to budding. The Influenza A virus does not control packaging of the nucleocapsid segments, so traits that are favorable to the virus could be acquired, as in resistance to interferon as mentioned above.20 The uncontrolled packaging also plays a part in mixed infections in which a virus could acquire a significant genetic change for the other virus leading to a potential advantage for the progeny on a larger evolutionary scale.19
>The immune system of the host is extremely dynamic. Its efforts to control, eliminate and prevent takeover by foreign matter are outstanding. However, the host is not the only dynamic entity. As selective pressures bombard the viruses, spontaneous minor mutations ( genetic drift ) and genetic reassortments ( genetic shift ) highlight the adaptive potentialities of the virus.21 Forms of genetic drift have already been described, but as in the case of a genetic shift not so much (Indulging in this topic leaves the scope of this writing and for the purposes intended, frequencies and likelihoods will not be presented). The potential of mixing of genetic information during a co-infection, in which two distinct influenza viruses in the same cell is possible.21 Such occurrence could lead to a novel species with a distinct evolutionary change rendering it extremely virulent.
One of the primary selective pressures leading to viral adaptability is thought to be humoral pressure by the host on the viral HA protein. This humoral pressure neutralizes viral attachment by blocking access to host receptors. However, these antigenic regions located on the globular heads of the HA protein can withstand numerous amino acid changes in the sequence of the protein. Thus, once effective, now the antibodies can no longer recognize the epitopes of the virus. This reasoning also illustrates why each year teams assemble to figure out what vaccine strain alterations are needed to keep up with the changing viral surface proteins.20
Stemming from talk of vaccinations, it should be noted that these provide mainly high levels of serum IgG, but low levels of IgA. The human influenza is a mucosal infection in the respiratory system, while the high-pathogenic avian influenza (HPAI) is also systemic. In a mouse model, it has been shown that the latter antibody was the most effective in the control of the virus.20 Also, it should be noted that the nucleocapsid segments are extremely stable relative to the surface proteins of the virus. Reasoning is based on the fact that these components are not efficiently presented by the MHC (Major Histocompatibility Complex) class I cells. This is probably good for the virus, for a change in these interior proteins could lead to impaired function in the replication of the virus.20
Host factors as it relates to the type of glycoprotein and its prevalence in the cell has lead to the viruses having a preference in the tissue type that is engaged in the organism. The host cell has glycoproteins with sugars located on the ends of these molecules. Generally, these are known as sialic acids and these molecules are further divided by which underlying sugar is attached to its alpha-2 (a-2) carbon.20 The most common linkages are a-2, 3 (avian) & a-2, 6 (human). Depending on which linkages are present in the host, a certain conformation of the host receptor will be presented. Appropriately, the viral HA protein amino acid sequence is such that it has a strong specificity for these linkages. Nonetheless, the amount and type of these linkages are different for not only species, but for tissue. Humans express both of these types of linkages and this distribution of these linkages illustrates the fact that pneumonia is more commonly seen instead of an upper respiratory tract infection. In humans, the alveolar type II cells in the lung tissue express a-2, 3 linkages. 20 It should be addressed that the specificity to a certain type of linkage is not limited to one type. Changes in the amino acid positions 226 and 228 of the HA protein can cause specificity to be altered.20 The porcine reservoir has been thought of as a potential "mixing pot" for novel viral strains. This reservoir has very high levels of both linkages in its respiratory system and so it has been proposed that avian strains and human strains could mix (genetically reassort), thus producing a novel strain. This proposition has been supported to the extent that some fairly complex viral strains have been isolated from this reservoir.20
Transition from Low-Pathogenic (LP) to High-Pathogenic (HP) Avian Influenza:
>The difference between low-pathogenic and high-pathogenic avian influenza is the degree to which the virus can cause disease and death in chickens. It should be noted that at this time only the subtypes H5 and H7 are known to have a high-pathogenicity type.20
One of the primary virulence characteristics that separates LPAI and HPAI is the ability of the HPAI virus to have host proteases cleave its HA viral protein.20 In order for the HA protein to be active, and thus allow the virus to be infectious, its HA protein must be cleaved into HA1 and HA2 subunits. Usually, the HA protein is cleaved by a trypsin type of protease that recognizes basic amino acids like arginine and lysine. Once cleaved, the HA2 region is exposed, which contains the fusion peptide that causes the membranes to fuse, which is necessary for release of viral RNA into the host cytoplasm. Thus, the presence of multiple basic amino acids upstream of the cleavage site results in increased virulence of the virus. 20 
>One of the most important parts of the HA protein is the region between the HA1 and HA2 regions, which is the proteolytic cleavage site (PCS). This is where addition of basic amino acids (arginine and lysine) at this site alters the cleavage region, which as noted above, increases the virulence of the virus. The reason why basic amino acids accumulate here has not been fully explained, but there are a few ideas on how they accumulate (These processes will not be described here, only a general description). The first is simple site mutations that occur do to the nature of the virus itself since it is prone to making mistakes. The second is the accumulation of three nucleotides at that region that results in a functional codon that code for a basic amino acid. The third is tandem duplications which entails the duplication of the nucleotides at the cleavage site resulting in multiple basic amino acids. The last is RNA/RNA recombination events in which RNA is inserted into the cleavage site.
As research continues to reveal mechanisms and processes of avian influenza and the roles it plays in humans, our understanding will increase, but for now it is best said as in "Avian Influenza", "Unlike our understanding of what makes AI viruses pathogenic for birds. Understanding the changes that occurred to allow adaptation for such a bird virus to mammals is not clear".20 Albeit it is "not clear", one thing evolutionarily speaking is, that if by misfortune, a devastatingly high-pathogenic form presents, it, by doing so, dooms itself to self-extinction.21
From Wild Bird to Domesticated Bird
>Avian influenza is carried in the intestines of wild fowl. These wild birds are generally unaffected by the virus and primarily serve as vectors for transmission 1. The spread from wild bird to domesticated bird (and therefore country to country) occurs when migrating birds share a water or food source with domesticated birds. The virus is spread through saliva, nasal secretions and even feces. Domesticated birds are often housed in very tight quarters, often with thousands of other birds, aiding in the spread of the virus. The spread can be facilitated from farm to farm and can happen unknowingly; for example, bird feces containing the avian flu virus can be carried from farm to farm via contaminated machinery, shoes, or rodents. “…A single gram of contaminated manure can contain enough virus to infect one million birds.” A bird infected in the morning can be dead by nightfall. H5N1 has almost a 100% mortality rate among domesticated birds. Currently, there is no treatment for infected birds; the only way to contain an outbreak is to destroy and properly dispose of the entire infected flock and anything that may have come into contact with them such as their feed and manure 2 .
>From Domesticated Bird to Human
Human infection occurs through direct contact with infected birds or contact with areas contaminated with excretions from infected birds1. It is the handling of contaminated poultry that results in viral spread, not the intake of the cooked poultry. In countries known to hold street markets, such as China, unknowingly infected chickens may be sold right next to fruits and vegetables2. Cross-contamination seems inevitable. A key reason why the bird flu originated in Asia is the close proximity to which the people live with their farm animals. Their animals often have free range and are allowed to enter their homes and play with their children. Farmers in Asia rely on poultry to feed and support their families and are therefore unlikely to kill off their entire flock if one bird becomes ill. Another thing to consider: those living in remote areas often do not have access to resources like the internet and may not even be aware the threat of the avian flu exists2.
From Domesticated Bird to Pig to Human
The Hong Kong Flu pandemic of 1968 was caused by the avian influenza strain H3N2. This strain arose as a result of genetic recombination of avian, swine, and human influenza strains via a pig intermediate. The virus was then able to readily pass from pig to human resulting in a pandemic that killed approximately 750,000 humans3. In August 2004, the WHO reported data from China’s Harbin Veterinary Research Institute confirming that pigs in China were infected with H5N1. These findings raise major concerns because of the pig’s previously demonstrated ability to be co-infected with multiple strains of the flu. If a pig were to be simultaneously infected with avian and human strains of the flu, it is possible that an even deadlier strain of H5N1 will emerge through genetic recombination and be able to infect human respiratory tissue and further evade the human immune system. The WHO suggests that further research be continued to “better understand the implications of these findings in China…”4.
>From Human to Human
For now, H5N1 does not easily infect humans. Few human to human cases have been reported, however viral mutation and therefore enhanced efficiency of a virus unknown to the human immune system is a major concern. According to the CDC, a case of human to human transmission was reported from Thailand in 2004. Also, in 2006 a case of one individual infected with H5N1 via contaminated poultry, transmitted the virus to 7 other family members1.
Cytokine Storm Theory
Click Here for Video on NEJM.org
Avian flu victims suffer from acute respiratory distress as a result of abnormal accumulation of fluid, pus and blood in and around the lungs. The severely congested lungs result in oxygen deprivation and eventual suffocation, and in extreme cases, can cause the lungs to hemorrhage and result in severe internal bleeding9. This excessive fluid accumulation is thought to be attributed to hyper stimulation of the immune system upon infection resulting in over-production of proinflammatory cytokines (hypercytokinemia) and can result in multiple organ failure 8. Normally, the immune response is self-contained; however, it is believed that in bird flu victims, the negative feedback mechanism is lost resulting in constant immune stimulation by infected macrophages to rapidly dividing T-cells or natural killer cells due the body’s inability to contain the infection8. This response has been termed a “cytokine storm” and is strongest in those with healthy immune systems (ie. young adults). These storms are “rare events” which makes them difficult to study; however, such “storms” are thought to be implicated in conditions such as Toxic Shock Syndrome and gram negative sepsis7.
Researchers in Hong Kong have demonstrated that victims of the bird flu and the resulting cytokine storm had “unusually high serum levels” of specific cytokines. The research compared cytokine production (specifally IP-10, RANTES, IL-6 and Interferon Beta) stimulated in bronchial and alveolar epithelial cells by human H1N1 virus (seasonal flu) with bird flu strains H5N1/97 (Hong Kong epidemic – 1997) and H5N1/04 (Vietnam epidemic – 2004). They discovered that, although the viruses replicated at similar rates, the amount of IP-10 and IL-6 secreted as a result of H5N1 infections were significantly greater than H1N1 at 24 hours post infection. Moreover, the researchers reported that the 2004 strain of H5N1 isolated from the Vietnam epidemic produced even greater amounts of IP-10 six hours post-infection than the 1997 strain of H5N1 isolated from Hong Kong. The amount of IP-10 produced by both H5N1 strains was comparable at 24 hours post-infection. The researchers also reported that, although RANTES mRNA levels in cells 6 hours post infection of H5N1 was significantly greater than the cells infected with H1N1, the amount of actual RANTES protein secreted by the H5N1 infected cells at 24 hours post-infection was only increased by a factor of four as compared to H1N1. The researchers were unable to detect Interferon Beta secretions even though it appeared that Interferon Beta mRNA transcrption had been significanty upregulated at 3 hours post infection of H5N1 as compared to H1N1. The researchers acknowledge that the mechanism behind the cellular response to H5N1 infection is “presently poorly understood”10 .
a) IP-10 >(Immune Protein-10): chemotactc protein expressed by monocytes, endothelial cells, kerantinocytes, fibroblasts and neutrophils. Along with other chemokines, may play a roll in pulmonary disease by attracting activated T-cells. IP-10 has been shown to inhibit angiogenesis. Elevated levels of IP-10 have been associated with necrotized tissue11.b) RANTES (Regulated upon Activation, Normal T-cell Expressed, and presumably Secreted) (aka: CCL5): A chemokine attracting T-cells, eosinophlis and basophils and known to cause desruction to microbes (microbicidal). Produced by T-cells, but inhibited upon T-cell activation. RANTES attracts white blood cells to sites of inflammation; also increases adherence of monocytes to endothelial cells. RANTES is also responsible for proliferation and activation of killer cells and causes basophils to release histamine11.
c) IL-6 (Interleukin-6): has both pro- and anti-inflammatory purposes. Secreted by T-cells and macrophages to initiate an immune response to trauma. IL-6 can also be released by macrophages in a response to microbes12.
d) IFN-B (Interferon Beta): Interferons are produced during a respone to viral infections. IFN-B is known to regulate genes that are involved in an antiviral immune response. The upregulation of such genes increase presentation of viral peptide by Major Histocampatiblity Complex I (MHCI) allowing cytotoxic T-cells (CD8 T-cells) to recognize and destroy the infected cell. IFN-B is also implicated in activation and proliferation of natural killer cells. IFN-B also inhibits apoptosis of memory T-cells. Research indicates that IFN-B may play a roll in chronic inflammatory responses and persistant T-cell destruction13.
>Patients who have been infected with the H5N1 virus will display lower respiratory tract problems early on, and will often have multiple organ dysfunction. To go along with these presentations other lab abnormalities may include:
- Leukopenia (mainly lymphopenia)
- Mild-Moderate thrombocytopenia
- Elevated aminotransferases
- Sometimes DIC15
Symptoms of the Cytokine Storm
The end result of the cytokine storm is multiple organ failure, but some of the other symptoms caused from the cytokine storms are:
- Hypotension
- Tachycardia
- Dyspnea
- Fever (temperature of >38°C or >100.4°F)
- Ischemia, (especially involving the major organs)
- Uncontrollable hemorrhage
- Multisystem organ failure (caused primarily by hypoxia, tissue acidosis, and severe metabolism dysregulation.)
To combat the affects of the cytokine storm drugs like ACE inhibitors and Angiotensin II Receptor Blockers have been shown to work. Also the Aventis vaccine has shown promising results in fighting the effects of the H5N1 strain.
Symptoms of Bird Flu
Bird flu is an infection caused by bird flu virus. Bird flu is greatly contagious among birds such as chickens, ducks, and turkeys. These flu viruses happen in nature. After people get virus infection, symptoms they have:
There are three ways to detect virologic diagnosis which include antigen detection, reverse transcriptionpolymerase chain reaction (RT-PCR), and viral culture. Antigen detection is used to test antibody against antigen. For example, “immunofluorescence test for antigen with antibody directed against H5 or a four-fold rise in H5-specific antibody titers can be used to detect infection” (Gladwin, p238). Viral culture and RT-PCR can be used to detect virus. For example, “RT-PCR of viral RNA from nasal or pharyngeal washings” (Gladwin, p238) is used to identify the virus. Patients’ feces can be detected for checking with a viral culture.Typical influenza symptoms
1. Fever
2. Cough
3. Sore throat
4. Muscle aches
5. Eye infection
More serious symptoms of bird flu
1. Pneumonia
2. Acute respiratory distress
3. Viral pneumonia
4. Other severe and life-threatening complications (Schoenstadt, p2)
PRE-INFECTION
More and more pharmaceutical companies and academic medical centers are looking for an effective vaccine. Passive immunotherapy has been used to protect against certain viruses for long time (Bird Flu, p1) For example, antibody-contain shots are very often for preventing bird flu. Until now, reverse genetics are used to quickly produce non-virulent vaccine viruses from H5N1 isolates (Gladwin, p239). Poultry vaccines are also used in some countries such as China, Indonesia (Control, p2).
Anti-viral drugs are given to patients who are infected with Avian Flu. These drugs are often used to fight human influenza. These drugs include:
1. Amantadine
2. Rimantaidine
3. Oseltamivir
4.Zanamivir (Control,P1)
These four antiviral drugs are alike effective in reducing the duration of illness.
Preventative measures
In order to prevent the spread to bird flu, many extreme measures are used as follow:
A. Keep poultry in closed poultry houses, the purpose of doing this is to
prevent contamination of wide areas.
B. Keep wild birds and their feces away from poultry and poultry feed.
They are resistant to poultry places because they may be carriers or
reservoirs of virus.
C. Seal poultry house attics and cover ventilation openings with screens.
D. Thoroughly and routinely clean all equipment, vehicles, clothing and
footwear before and after coming into contact with poultry. Birds shed
large amount virus through their feces and nasal passage.
E. Ensure proper hygiene practices for all persons coming into contact with poultry.
F. Maintain high sanitation standards in and around poultry houses
G. Isolate or avoid introducing new birds into existing poultry flocks if their health status is unknown.
H. Limit access to poultry houses, such as farm workers, feed suppliers, poultry veterinarians, catching crews, sawdust and shaving suppliers, agricultural service personal and casual visitors.
I. Avoid using water in poultry houses contaminated with feces from wild birds.
J. Maintain a log of all visitors coming into contact with poultry (Control, p 1-2).
All procedures above may slow the spread of virus and help to reduce the contamination of poultry with the virus.
Federal
Secretary Michael O. Leavitt of the HHS stated: “Preparation is a continuum. Each day we prepare brings us closer to being ready. We are better prepared today than we were yesterday. And we must be better prepared tomorrow than we are today” 37. The United States government has involved many federal agencies, such as HHS, USDA, CDC, and DOI, and has been working with the WHO in order to plan for, detect, and respond to the upcoming pandemic. Domesticated and wild birds are being monitored to track where the virus may be currently and where it may be headed; vaccinations are being prepared from different strains isolated from outbreaks; anti-viral drugs are being tested on the different strains to make sure they are effective. State and local authorities, along with schools, businesses, and healthcare facilities are being educated on how to respond. There are many checklists to assist all areas of society in preparing for this pandemic. Organizing and stockpiling medical supplies is a major division of planning. The Strategic National Stockpile (SNS), also known as “12-hour Push Packs”, is a federal program managed and maintained by the HHS and the CDC. It is designed to provide large amounts of medicine and medical supplies to a given area of the U.S. , or its territories, in the event of a public health emergency (terrorist attack, earthquake, infectious outbreaks or any other public health disaster). The HHS and CDC, along with other federal agencies, are responsible for evaluating the situation to determine and release the appropriate assets. Once federal and local authorities give authorization to ship the SNS, they will arrive on site within 12 hours and the Technical Advisory Response Unit (TARU) will be organized to efficiently receive and distribute assets to appropriate areas35, 36 . The SNS contains antibiotics (oral and IV) and other medications, bandages, vaccines, chemical antidotes, antitoxins, life-support medications, IV administration, airway maintenance supplies, personal protective equipment, and medical/surgical items 36. For this predicted pandemic, the SNS has been stockpiling enough anti-virals to administer to more than 7 million people. It has also stockpiled around 8 million doses of vaccine against the H5N1 strain that was isolated from Vietnam in 2004. This vaccine requires two doses, so 4 million people could be vaccinated. There is also development of a vaccine on the H5N1 strain isolated from Indonesia in 2005. Since the H5N1 strain is continually evolving, it is difficult to produce and stockpile one specific, and effective, pre-pandemic vaccine 37.
State
>Each individual state is responsible to coordinate the influenza pandemic response within its own jurisdiction 40. The federal government has given each state appropriate funding to use for pandemic planning and preparation—phase one allocation was given in January 2006, phase two allocation in July 2006, and the last allocation was given in August 2007. The Pandemic Flu website includes a table that breaks down the allocations given for each state. Each state should be not only be prepared to assess health and medical needs, but they should have in-hospital care, drug and vaccine safety, medical equipment and supplies, mental health care, vector control, veterinary services, shelters, coordination with SNS implementation, and much more. With the assessment of health and medical needs in the pre-pandemic phase, the amount of effective influenza vaccine available needs to be determined and distributed to the states and territories; they must work with the District Health Departments and CDC to monitor the amount of vaccines coming into the states each year along with coordinate with the Board of Pharmacy to monitor anti-viral usage and need 40.
Local communities
Health Care
Health care workers should continually be educated on the pandemic influenza. They must be alert to any emerging respiratory diseases, receive the annual influenza vaccine, know the uses of personal protective equipment, have alcohol-based hand sanitizer distributed throughout facility, plan for any disruptions in sanitation, power, water, and food supply, and have access to a sufficient supply of anti-viral and anti-biotic medications and commonly prescribed medications (such as warfarin and insulin). An effective vaccine for the particular strain that will strike may take from 2 to 6 months after the first wave to produce therefore healthcare must rely on antiviral medications in the meantime. On the flip side, however, there won’t be enough supply of antivirals, and the virus may develop resistance to the antivirals making it ineffective, so that is why it is important to take the steps to plan and prepare in order to properly respond to and try to prevent illness 43, 44. Healthcare facilities must develop protocols for disease surveillance, hospital capacity, ensuring infrastructure, communication patterns, isolation and quarantine, lab evaluation and diagnosis, mortuary storage capacity, and much more. Practicing influenza pandemic response exercises and drills is also recommended. Facilities may be short-staffed, so they should consider cross-training staff in crucial areas, including the emergency department or intensive care units. Hospital security, along with State and Federal law enforcement, may also need to be involved to maintain order in the facility 44.
>Schools
Given that about one-fifth of the population of the United States either works in or attends schools 41, it is critical to protect the health of that population in order to keep infectious diseases, such as the avian influenza, under control 42. Timely, community-wide school closures can reduce peak attack rates of the pandemic flue by 40%; however school closures may not have as much of an impact on overall attack rates. Isolation of individual cases and household quarantine could have a greater influence 34. Each state has its own set of laws on school closures in the event of a flu pandemic, and the term “school” can include private and public schools and kindergarten through twelfth grades. Using the U.S. Federal Response Stages (ranging from 0-6), it is suggested by the CDC for the government to start considering school closures at stage two or three, and highly recommended that schools close at stage four or five. Schools may be closed for up to 12 weeks depending on the severity of the pandemic. There are checklists that can be used for preschools, school districts (K-12), and colleges and universities in order to help plan and prepare. Not only are school closures recommended to prevent spread of disease, these buildings could be used as shelters or care centers for temporary use 42.
>Businesses
Businesses must plan and prepare not only to protect their employees’ health and safety, but to protect the economy from any negative impact H5N1 may invoke. OSHA has created different risk levels of occupational exposure depending on the type of workplace. It ranges from very high, which includes healthcare and laboratory workers handling specimens, to low, which includes people with minimal contact with the general public. A majority of the American workplaces are at medium to low exposure level. Even at the lower risk level, employers still need to prepare. They should have continual education on the matter, develop a policy for sick leave, encourage employees to receive the annual flu vaccine, create a plan of response, and stockpile anti-viral drugs along with personal protective equipment. Employers should also implement proper hand washing technique, cough/sneeze etiquette, and social distancing if possible. Installing no-touch trash cans, water faucets, and hand soap, and providing tissues, disposable paper towels, and disinfectants to clean work area with is recommended. Keeping work areas clean, such as tops of desks, computer equipment, phones, and other frequently touched surfaces can help minimize spread of disease 45, 46.
Faith-based
Worship services and any other religious gatherings may be cancelled in the event of a flu pandemic, so church organizations should have a communication network set up in order to inform all participants of any cancellations. Religious leaders may need to encourage congregants to stay at home and practice social distancing if they become sick. Church buildings may be used as temporary shelters or care centers, and if any congregants have any skills in the health profession, it should be made known to local health authorities 47.
Families and individuals
Every person needs to be prepared because every life will be affected by the impact of this upcoming pandemic. Although government agencies are doing all that they can, individuals need to educate themselves on how to better prepare themselves and their families. As stated already, schools, healthcare facilities, grocery stores, transportation services, telephone and cell phone companies, banks, post offices and other government offices may be disrupted or closed during this time. Therefore, food and water supplies may be limited and individuals may not be able to go to work. The effects of the pandemic may be less severe on individuals and their families if they plan ahead. There are flu pandemic checklists for families/individuals, along with emergency health information sheets and emergency contact forms that can be used as guidelines. Those with disabilities and/or special needs should make sure they have appropriate arrangements in the event of a pandemic. They need to have all the proper materials to survive on until the pandemic passes and they should discuss with family, friends, or neighbors about getting help when the pandemic strikes. If a person has a disability where they require the assistance of an animal, special arrangements need to be made for it as well 38. Pets can be important members of a household so it is important that they are included. Adequate food and water, collars, tags, leashes, and any medications the animal requires are all important when it comes to planning 39.
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http://panfluidaho.org/media/panflu_pdfs/businesses/It%27sNotFluAsUsual_Business.pdf