Preparing for a Potential Avian Influenza Pandemic

By Linda L. Williford Pifer, PhD, SM(ACM), GS(ABB)

This offering expires June 19, 2008

Upon completion of this Learning Scope, readers should be able to:

1. Describe the mutable nature of influenza viruses; how strains A, B and C differ; and the difference between antigenic drift and shift.

2. Explain modes of transmission of the virus, its vectors and how to most effectively prevent it in the clinical laboratory environment and in society in general.

3. Recognize the epidemiologic and clinical differences between seasonal 2005 influenza (vaccine already widely distributed) and avian H5N1 influenza.

4. Identify symptoms of the varieties of influenza virus as defined by the CDC.

5. Understand which laboratory safety and diagnostic procedures must be undertaken.

6. Know specifically which CDC and local health department contacts to notify if avian influenza is suspected.

7. Formulate a pandemic plan for laboratory staffing.

8. Maintain adequate and appropriate protective equipment.

9. Learn names (commercial and generic) of antivirals available in your region, and how they may be made available if the need arises.

10. Increase awareness of potential threat and have a lab game plan, including knowledge of biosafety levels and preventive measures.

Introduction/Commentary

Frankly, at this writing, neither crystal ball nor prophet has come forth to tell us exactly what to expect regarding avian influenza. We can only look into the past, and it is said that those who forget the lessons of the past are doomed to relive them. It is hard to know how intense our response should be in planning for a potential avian influenza pandemic, but if we err, it absolutely must be on the side of caution. Since Dec. 26, 2004, we have seen unprecedented natural catastrophies (in modern history). Is another one coming on the wings of migratory birds and global travel?

The purpose of this treatise is to educate, warn and prepare laboratory professionals for the worst, whether it comes or not. Even if the threat of avian influenza fades into obscurity, it should have a positive impact on our readiness status for assault by other infectious diseases, which continue to emerge or be recognized.

The bottom line is that we must be READY (Regions Empowered Against Disaster: YOU). Readiness does begin with you. This includes laboratorians from every region of this country—all of us. Even the potential of a pandemic should serve as a call to arms to ready and empower ourselves against what may or may not evolve into the worst infectious disease disaster since the emergence of HIV (recognized in 1981) and "Spanish influenza" (1918).

The Nature of Influenza Viruses

Influenza viruses belong to the Myxoviridae family of RNA respiratory agents that are further subdivided into groups A, B and C. Type C usually is nonepidemic and does not infect domestic animals. Type B is a more serious problem, and definitely can cause epidemics. Again, however, it does not infect domestic animals.

Our most critical concern at present is type A influenza, which has caused global pandemics, and can infect humans, pigs, many other animals, and wild and domestic avian species. It has literally changed the course of human history over the centuries and caused a raging pandemic in 1918: the infamous Spanish Influenza.^1,2 The 1918 worldwide outbreak accounted for about 80 percent of all deaths in the U.S. military during World War I.³

The major problem is the mutability of influenza A. Genomic instability is characteristic of influenza A and HIV. We need new influenza vaccines each year due to what is termed antigenic drift, or small but significant changes in the sequence of the genome of the virus. Each year, scientists from St. Jude Children's Research Hospital, Memphis, TN, in concert with the WHO and other scientists, collect specimens of the most prevalent strains of influenza months before the infection reaches the West, and appropriate vaccines are prepared. Antigenic shift reflects a much more radical change in the virus and has resulted in numerous quite deadly pandemics during the 20th century. We are facing an antigenic shift in avian influenza.

Type A influenza viruses, of which there are many varieties, possess two major antigens that promote infectivity: hemagglutinin, which allows the virions to dock with susceptible cell membranes; and neuraminidase, an enzyme which essentially perforates cell membranes, aiding both entry and exit of the virions from cells.

The dangerous problem that this presents is that there are at least 15 different hemagglutinin antigens and nine possible neuraminidase antigens. Every known influenza A strain contains one of the 15 H antigens and one of the nine N antigens, thus the common seasonal influenza that we expect this season and into 2006 is the H3N2 strain.

Influenza A, however, has the theoretical potential for producing as many as 135 different antigenic sub-variants. What we fear most is a potential pandemic of H5N1, which we now know caused the horrific death toll in the Spanish Influenza.

Thus Far

Since 1997 in Hong Kong, avian influenza has infected humans who contracted the virus most probably via respiratory transmission from handling domestic fowl. We now know that what was most dreaded may have happened: human-to-human respiratory/contact transmission.

As of May 29, 2006, there have been 224 cases of H5N1 influenza in humans, and 127 deaths in 2006. The mortality rate is approximately 57 percent.⁴

If quarantine and the destruction of infected domestic fowl fail, the West could be facing the worst pandemic in living or recorded history, because the mortality rate for H5N1 exceeds 50 percent. Presently, there have been no known cases of H5N1 influenza in humans, fowl or other animals in North America. Our greatest threat at present appears to be global travel and seasonal migration of wild fowl from east to west. The H5N1 strain kills chickens, but migratory water fowl may act as Trojan horses, carrying the virus, but not necessarily dying from it.

Symptoms

Avian influenza shares many features of common seasonal influenza, with several noteworthy exceptions. For a continually-updated CDC definition of H5N1 symptoms, go to www.cdc.gov, as this information changes as more data are gathered. Generally, however, persistent fever, coughing, sore throat for up to 6 days, dyspnea, pneumonia and adult respiratory disease syndrome (ARDS) followed by respiratory, renal and/or cardiac failure have been documented. According to one research team, lymphopenia is predictive of mortality.⁵ (Note: all divisions of the laboratory should be aware of these potential clinical warning signs associated with H5N1, not just virology/microbiology.)

The type of neuraminidase antigen associated with the current H5N1 avian virus was noted in tissues derived from victims of the 1918 pandemic.⁶ The N1 neuraminidase antigen is particularly virulent in setting the stage for secondary bacterial pneumonia.⁷ Hemagglutinin H5 caused severe lung damage in the 1918 pandemic.⁶ The body's own immune system reacts dramatically to the incoming antigens and cytokine storms result, which, paradoxically, further worsen patients' condition.

Prevention

First, anyone who has not been immunized against the common variety of influenza prevalent this year (H3N2) should do so without delay, unless a physician advises against it. This is particularly true for high risk individuals who are described at www.cdc.gov. This vaccine will offer no significant protection against H5N1 if the latter appears.

However, we must prevent the two strains from mixing and recombining in the human host. This conceivably could add fuel to the fire. Certainly every citizen should maintain a month's supply of food, water and essential medications. Since the tsunamis of late 2004, we have graphically seen what can happen when we are not as prepared as possible for disaster.

Handwashing and use of alcohol rubs, especially in public places, are vital. We are likely to see the use of masks in public, as was employed in 1918. If H5N1 comes, or rather when it comes, quarantine may become essential if the vaccine that is currently in production is unavailable in sufficient quantities.

According to Julie Gerberding, MD, director of the CDC, the U.S. is making rapid progress, but the bottlenecks in production have resulted in far less than adequate supplies.⁸ We are genuinely in a race against time. Vaccine production generally requires at least 6-9 months or longer.

Laboratories should put plans in place immediately to decide on policy. Needless to say, this will cause economic concerns and staffing problems. Personal protective equipment (PPE) as described by CDC should be available should avian influenza break out. Laboratory personnel are essential, but seriously ill staff, particularly those with the severe symptoms described previously, should stay home. At the very least, there should be a list of first, second and third tier laboratory professionals who are willing and able to respond during any crisis. Essential medical personnel should have high priority access to Tamiflu^® (oseltamivir) and any other antivirals deemed useful in such an event. Should medical support crash during such a circumstance, we could find ourselves in a viral atmosphere with no one available to manage or even diagnose exceptionally ill patients. Every precaution must be taken to maintain clinical/diagnostic personnel in a viable state.

Regrettably, there already is evidence of possible resistance of H5N1 to Tamiflu, which is a first line defense antiviral manufactured by Roche Diagnostics, Basel, Switzerland from the plant star anise, with shikimic acid as one of the critical ingredients. It is known that early administration of Tamiflu is associated with a significantly improved survival rate.

It is not yet firmly established that these cases represented genuinely resistant sub-variants of H5N1 or whether the dosage must be increased. The drug must be given within at least 48 hours from the onset of symptoms. In the mouse animal model, Yen, et al, tentatively concluded that an 8-day regimen was superior with regard to survival, to a 5-day course.⁹

Other potential antiviral drugs include zaminivir, amantadine and rimantidine, although their effectiveness against H5N1 is not fully known at this time. The federal government already has met with pharmaceutical firms that have been given reassurance of protection to an extent from liability arising from lawsuits claiming illness associated with antiviral drugs and vaccines. Roche already has subcontracted its formula for Tamiflu to several companies in other countries.

Time may not be on our side, but no one knows for sure. Perhaps measures being taken now in Asia will slow the nearly inevitable approach of this exceptionally dangerous virus. It may come in 2006, 2008 or even later, but it will almost surely come, given the conditions that presently exist. Klaus Stohr, head of the WHO's influenza division, has issued uncharacteristically strong warnings about the advance of this potential pandemic.

Diagnosis

The diagnostic clinical laboratory will be first to know decisively if H5N1 is present locally. Nasopharyngeal and oral swabs should be tested by cell culture and reverse transcriptase-PCR, using appropriate biosafety precautions.

A new PCR-based test developed by Roche, which can be performed on LightCycler™ instruments, will permit researchers to identify H5N1 within hours, rather than days.¹⁰ Acute and convalescent sera can also be tested via neutralization and enzyme-linked immunosorbent assay (ELISA). A four-fold rise in antibody titer is virtually diagnostic of any viral infection.

If H5N1 virus is identified in your community, all respiratory specimens must be managed at Biosafety Level 3, most particularly if the virus is cultured.^1,2 Viral culture and PCR are still recommended in preference to rapid tests.

Essential Contacts

Make it your goal to be prepared and have information at the ready in the event of an outbreak of H5N1 avian influenza. The sites listed in the Table are extremely valuable and you should consider making contact now with the local, state and CDC authorities to obtain the latest advisories.

References

1. Pifer LLW: A plague on wings. ADVANCE for Med Lab Pro 2004;16(23):12-14.

2. Pifer LLW: Avian influenza. ADVANCE for Med Lab Pro 2005;17(23):22-24.

3. Travis WD: Atlas of Nonhuman Pathology, Chapt. 10, 2002, American Registry of Pathology.

4. Cumulative number of confirmed human cases of avian influenza A/(H5N1) reported to WHO. Available at: www.who.int. Last accessed June 6, 2006.

5. Chotpitayasunondh T, Ungchusak K, Hanshaoworakul W, et al. Human disease from influenza A (H5N1), Thailand, 2004. Emerg Infect Dis 2005 Feb. Available at: www.cdc.gov/ncidod/EID/vol11no02/04-1061.htm. Last accessed June 6, 2006.

6. Kobasa1 D, Takada A, Shinya K, et al. Enhanced virulence of influenza A viruses with the haemagglutinin of the 1918 pandemic virus. Nature 431:703-707, 2004.

7. Peltola VT, Murti KG, McCullers JA. Influenza virus neuraminidase contributes to secondary bacterial pneumonia. J Infect Dis 2005;192:249-257.

8. How to report to CDC. Available at: www.aphl.org/membersonly/index.cfm (password required).

9. Yen H, Monto AS, Webster RG and Govorkova EA. Virulence may determine the necessary duration and dosage of oseltamivir treatment for highly pathogenic A/Vietnam/1203/04 influenza virus in mice. J Infect Dis 2005;192:665-672.

10. ADVANCE for Medical Laboratory Professionals. New PCR-based test for bird flu becoming available for researchers. Available at: http://www.laboratorian.advanceweb.com/Editorial/Search/AViewer.aspx?CC=62296 (login required). Last accessed June 14, 2006.

Dr. Pifer is a professor in the department of clinical laboratory sciences, College of Allied Health Sciences, University of Tennessee Health Science Center at Memphis. No endorsement by the author or her academic institution should necessarily be construed for any medication described in this publication.