Assessing the Threat: The Potential Avian Influenza Pandemic

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Biology 103
2005 Second Paper
On Serendip

Assessing the Threat: The Potential Avian Influenza Pandemic

Nick Krefting

Recently, there has been a lot of media coverage on a relatively new strain of avian flu in Asia. This strain has infected a small number of humans in a few Asian countries, but the implications of these few infections are potentially disastrous. Government officials, and obviously health organizations, are concerned about the risk of a mutation in this strain that could lead to a pandemic. (1) An epidemic is an illness that affects a relatively large proportion of a given geographical population; a pandemic is an epidemic that affects a much larger geographical area. This paper aims to assess the potential risk of the current situation, but first it is necessary to examine some background information on influenza viruses in general.

There exist three general types of influenza A, B, and C. Types B and C generally affect only human, and neither cause pandemics. Type C usually only leads to a mild illness, and though B is typically more dangerous, its spread has remained limited to epidemic status in the past. The current avian flu is type A influenza. Type A is a broad category that affects a number of species, and is divided into various subtypes, which are then further divided into strains. The term "subtype" refers to the "type" of two proteins on the surface of the virus: hemagglutinin (H) and neuraminidase (N). There are various subtypes of these two proteins, leading to a wide variety of subtypes for the influenza A virus. These subtypes are named according to the type of both proteins present for example, the first of each type is designated H1N1. (2)

The subtype that is currently threatening pandemic status is the H5N1 influenza A, which is primarily carried by and transmitted between birds. (3) In 2003 and early 2004, there was an outbreak of H5N1 in eight Asian countries that caused the deaths of over 100 million birds. The subtype reemerged months later, and the current outbreak has not yet subsided. (4) As of October, infected birds have been found as far west as Turkey, Croatia and Romania. (5)

This spread of the virus is not immediately harmful to humans; it is the potential of the virus to mutate that creates a problem. The current strain of the H5N1 virus has an extremely low rate of transmission from birds to humans; just over 100 people have been infected since the first appearance of the virus in 1997, a negligible number compared to the multitudes of infected birds. (6) The virus in its present form is also not transmissible between humans. Thus, in its current incarnation, the virus is not terribly dangerous, though, if certain conditions were met, the virus could become extremely dangerous.

The first alarming fact about H5N1 in humans is that, of the few humans who have been infected, over half have died from the illness. (6) Even this fact fails to be that significant if humans catch the virus only rarely. The known nature of viruses, however, dictates that there is a lurking threat in the form of a mutation. Though not currently transmissible between humans, every infection of a human by a bird increases the likelihood that H5N1 will mutate to form a strain that can be transmitted from human to human.

All this raises some extremely frightening questions, many of which simply cannot be answered. The virus needs only one mutation in order put the human population in very direct danger of a pandemic. Vaccinations are not yet developed, of course, because the human-to-human strain, from which we could derive the vaccine, has not yet evolved. What, then, can be done to prepare for a pandemic? How widespread would it be? How worried should a citizen of the world be about contracting a fatal strain of H5N1?

Various sources treat the possibility of the pandemic with slightly different levels of seriousness. The most sensible information is put out by the WHO, which is concerned about health risks for the entire human population. Their avian flu fact sheet (6) emphasizes that the threat of the necessary mutation is ever-present and becomes increasingly potent as the geographical area of infected birds grows. They urge countries take all possible action before the pandemic to prepare, and warn countries to follow plans (developed by the WHO) for isolating the virus and minimizing its spread during a pandemic situation. (7) This is extremely practical and reasonable information, urging decreased interaction between humans and birds who could be carriers to try and stem the tide. This focus on prevention, if listened to, could be extremely useful; just in case, though, the WHO still provides instructions in the event of an outbreak. Overall, their advice is useful, and could easily prevent a worst-case scenario.

The CDC of the United States treats the avian flu seriously, but they have a different angle from the WHO. The CDC downplays the immediacy of a pandemic event, and their fact sheet (4) suggests that the best strategy is very close surveillance rather than immediate preventative action. This probably stems from the CDC's status as a US organization, concerned primarily with health risks to US citizens Americans can not take as much preventative action as can citizens of Asian countries. Similarly, the CDC prioritizes the eventual importance of vaccines over preventive measures. This strategy is echoed by a recent $7.1 billion bill proposed by President Bush, of which all of the money will be spent on researching or buying vaccines and buying antiviral medication. (8) In America, the pandemic is not seen as an immediately preventable threat, but rather as a distantly inevitable threat.

That being said, both agencies agree that the risk of a pandemic is very serious and that precautions should be taken. Most of the difference between the two approaches lies in their assessment of the probability of a H5N1 pandemic affecting the population with which they are concerned. The WHO's overall plan, while it does include plans for vaccination and antiviral medication, spends much more time on practical methods for reducing the threat of the pandemic. This, to me, seems a far saner method. Prevention shouldn't be left out of the picture just because it doesn't affect one portion of the population as strongly.

1) "Administration's Flu Plan Gets Mixed Reception in Congress", New York Times 11/3/05.

2) The CDC's Influenza Virus Fact Sheet.

3) National Biological Information Infrastructure's Overview of Avian Influenza.

4) The CDC's Avian Flu Fact Sheet.

5) The WHO's Avian Flu Timeline.

6) The WHO's Avian Flu FAQs.

7) WHO's Recommended Strategic Actions in the event of an Avian Flu Pandemic.

8) "Bush Announces Plan to Prepare for Flu Epidemic", New York Times 11/2/05.

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