Facts About the Bird Flu

Pandemics

First, let’s discuss flu pandemics. (Most of the facts I give about pandemics come from Flu by Gina Kolata.) The flu virus exists in a variety of unique genetic strains. Once someone is infected by a strain, or receives a vaccine, the body develops antibodies which are effective against that particular genetic variant. Future infections are more easily resisted because the body is primed to produce the antibodies. A pandemic occurs when a new genetic variant comes into existence, and they typically spread worldwide. The last pandemic was in 1967, and the most famous was in 1918. The 1918 Spanish flu pandemic is estimated to have infected a quarter of the world’s population and killed 20-40 million people. It is believed that more World War I soldiers died from the flu than from combat.

All new flu strains come from Asia. As of 1999, all pandemics that had been traced to their source were found to have originated in a single Chinese province. This is not a coincidence. There is a unique juxtaposition on Asian farms creating a fertile breeding ground for new flu strains—the close intermingling of birds, pigs, and humans. New variants of the flu start in birds such as ducks or geese, but it’s very difficult for the virus to make the jump directly to humans. This is where the pigs come in. Pigs are “closer” to humans, in a genetic sense, than most other non-primates. But they’re also genetically closer to the birds than humans are. So the virus makes the jump to the pigs, where it mutates some more, and is then able to make the jump to humans. In general, humans can’t catch diseases from very many farm animals, but pigs are an exception. (Ever wonder why cannibalism is impractical from a strictly biological point of view? It’s because we can easily get diseases from the flesh. Ditto with pork, which is close enough genetically to be able to pass on some disease whereas other animals are not. I believe this is why some religions prohibit the eating of pork.) Another possibility, which does not involve pigs, is that the virus jumps directly from birds to humans and then combines with existing human flu variants such that it can transmit between humans.

For a pandemic to occur, the virus must (1) be a new genetic strain, (2) make its way to humans, and (3) mutate so it can transmit between humans. Or, as USN&WR put it: “First, a virus emerges from the pool of animal life that has never infected human beings and is therefore one to which no person has antibodies. Second, the virus has to make us seriously ill. Third, it must be capable of moving swiftly from human to human through coughing, sneezing, or just a handshake.”

The H5N1 Virus

So let’s get back to the current situation. The new flu strain is officially named H5N1 and currently exists in hundreds of millions of birds. It has, in a few cases, made the jump directly from bird to human. The percentage of deaths is high—of the 100+ people infected so far, about 50% have died. There is a good possibility it will (1) make the true jump to humans, and (2) mutate enough that it can be transmitted from human to human. At which point the pandemic will begin and people will die. Health officials are trying very hard to stamp out the bird flu, which involves killing a lot of birds (e.g. millions), but this effort is expected to take years.

The good news is that the pandemic will begin in Asia, most likely Vietnam or Thailand, and spread to the rest of the world. So those of us in North America may have a reasonable amount of time to get vaccinated. Some estimates are as much as 3 months for it to spread worldwide. I have, however, heard worst-case scenarios of 3 days. It depends on the specifics of the mutation of the human version of H5N1. There are, however, two problems. First, it takes a significant amount of time to make hundreds of millions (or billions) of vaccine doses, especially given the archaic methods used to create them (eggs, for god’s sake!). Depending on how quickly the virus spreads, the vaccine may not be ready when the pandemic hits. Typically it’s not possible to make a vaccine for a new flu strain until the pandemic is already underway. But world health organizations believe they can make a less-effective version of the vaccine which may not prevent a person from getting the flu but may keep him/her from dying. The US government has ordered 4 million doses of this preliminary vaccine, and other national governments are stockpiling some as well. This is obviously not enough to vaccinate everyone, and I’m assuming these doses would go to health-care professionals. The second problem is that it takes two vaccinations to be protected from a new strain of the flu, not just one like we normally get. I’m not sure how long you have to wait between vaccinations, but it adds to the time delay before you are immunized, thus increasing the chances of contracting the flu. The preliminary vaccine, however, would actually “prime” you for the new strain, and it would only take one shot of the pandemic-specific vaccine to be fully immunized. There are also antiviral medications such as Tamiflu which may be helpful.

World health officials are doing all they can, but the general attitude is that it’s a matter of “when” not “if.” When the bird flu becomes a reality, be prepared. Get vaccinated as soon as possible. Find out how to minimize your risk of exposure and get educated on its deadliness and transmission rate.

Update [2005-8-19 20:2:49 by chad]: The bird flu has made its way to migratory birds and, as a result, is now infecting birds in Western Asia (Mongolia, Russia, and Kazakhstan). This raises the specter that it may soon spread into Europe. While it’s still probable that patient zero will be in Vietnam, Thailand, or China, this raises the possibility that the pandemic will start elsewhere.

Update [2005-10-14 8:34:33 by chad]: The bird flu has been in the news lately. As expected, migratory birds have carried it to Europe—it has definitely reached Turkey and is suspected in Romania—although there are no human cases yet. The US government is beginning to realize that a bird flu pandemic could be a national disaster, and President Bush has requested the ability to use the military to enforce quarantines in the case of a pandemic. In addition, clinical trials on a “preliminary” H5N1 vaccine are underway, but there are problems—we simply may not have the production capacity to create enough doses of the vaccine in the time needed, and many of the companies involved are reluctant to start expensive human trials without a guaranteed market.

References & Resources

I will be updating this article on an ongoing basis. If you discover any news on the topic, or have any suggestions, comments, or corrections, please feel free to contact me.

Copyright © 2005 by Chad Cloman

3 thoughts on “Facts About the Bird Flu”

  1. Flu is not the only disease originating from the unique situation in southern Asia. SARS should still be fresh in our memory. The most recent development is a mysterious “pig disease” which the Chinese government is blaming on a known human pathogen, Streptococcus suis type II (a bacteria, not a virus). The mortality rate and infectiousness are higher than in previous S. suis infections, raising questions about whether the bacteria has learned some new tricks or has been wrongly implicated. The World Health Organization recently asked for more tests.

  2. Nice posting Chad. I hope this item will act as a focal point for future discussions. Just to throw in my tuppence worth (about 5 cents), I reported from a Royal Society meeting after the SARS outbreak. My reporting on emerging viral infection can be found here.

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