Bird Flu: Time to Get Ruffled?

Who would have thought that the return of SARS would not be the big health news this year?

Instead, the headlines are full of avian influenza, commonly known as bird flu, which is rapidly spreading across Asia. How worried should you be about this new threat? Is it time to give up chicken? Stop eating eggs? Fly home?

Avian influenza viruses are a subset of Type A influenza viruses that infect birds, pigs, horses, seals and whales. Some types also infect humans. Though avian influenza viruses don't usually directly infect humans, they can cause severe illness and death in domesticated birds.

Since 1997 there have been several outbreaks that have caused human infections. The first of these, in 1997, saw 18 human cases recorded in Hong Kong, resulting in six deaths. All of these instances of human infection with avian influenza viruses have in fact been very limited － but whenever they occur, public health authorities worry about the potential for wider transmission among humans.

In the Hong Kong outbreak of 1997, the rapid, comprehensive response by the Hong Kong health authorities － the entire poultry population of the territory was destroyed within three days － is believed by many experts to have averted a pandemic.

The current outbreak of bird flu is affecting many countries in Asia, including Japan, China, Thailand, Indonesia, Cambodia, Vietnam, Korea and Laos. It is causing widespread devastation to the poultry industry and has resulted in some human infections and deaths. The strain of bird flu involved, H5N1, is what is called a highly pathogenic avian influenza' (HPAI), haracterized by sudden onset, severe illness and rapid death in poultry, with a mortality rate approaching 100% in birds. In Thailand and Vietnam a number of human cases have occurred; still a very small number overall, but with a high mortality rate. As Beijing This Month went to press, 13 of the 17 people infected had died.

In its current form, the H5N1 virus is not a significant risk to the general population. Infections have occurred almost exclusively in those who have direct contact with live poultry. Reports in the last few days that two cases may have been spread from human-to-human (from an infected person to the two sisters caring from him) are also not yet reason to panic － in other H5N1 outbreaks very limited human-to-human transmission has also been documented. But this form of transmission is too inefficient to pose a risk to the general population at this time.

So why all the fuss?  Aside from the devastation to the poultry industries of many countries in Asia, the concern is actually for what might happen in the future. The larger and more widespread the avian influenza outbreak in poultry, the greater the chance for more humans to become infected through bird-to-human transmission. And the more humans that are infected, the greater the chance that someone will be co-infected with an avian influenza virus and a human influenza virus at the same time.

If this happens, there is a chance that a new virus could emerge － as severe as the avian influenza, but also easily transmissible from person-to-person. There would be little or no immunity to such a virus in the general population and current vaccines would be ineffective, so the virus could spread rapidly around the world. Such an event would mark the start of an influenza pandemic.

Influenza pandemics occurred three times during the twentieth century. The worst of these was the Spanish Influenza of 1918-1919 (a misnomer since it probably started in China), which killed somewhere between 20 million and 50 million people － far more than the war which preceded it. In fact, it was the most devastating epidemic in recorded world history, killing more people in a single year than died in all four years of the Black Death Bubonic Plague. The other two pandemics － the Asian Flu outbreak of 1957-58 and the Hong Kong Flu outbreak of 1968-69  were less severe but still caused a great deal of illness and death.

While the thought of another pandemic is scary enough to get public health authorities very worried, it is important to emphasize that at this point the risk is purely theoretical.

The bird flu does not CURRENTLY pose a significant risk to the general population. A great many experts are working very hard to try to keep it from becoming a risk in the future and to fast-track vaccine development in the event of a pandemic. The most important measure right now is the rapid and safe culling of all infected or exposed poultry in countries experiencing outbreaks of H5N1 avian influenza.

You do NOT need to stop eating chicken or eggs, as long as they are thoroughly cooked. The following is the advice of the CDC (Centres for Disease Control) and WHO (World Health Organization):

• Avoid poultry farms
• Avoid contact with animals in live food markets
• Avoid surfaces that appear to be contaminated with faeces from poultry or other animals
• Cook poultry and poultry products thoroughly
• Avoid cross-contamination of surfaces during poultry preparation
• Practice good hygiene, including attention to hand washing

The latter four points are just precautionary measures. In any case, this common-sense advice will also prevent Salmonella poisoning! I might also add that it is probably a good idea to stay away from live poultry in local villages. Aside from these simple measures, further precautions are not necessary at this time.

To keep up-to-date with the avian influenza outbreak, the following are good sources of information:

The World Organization for Animal Health:

www.oie.int

The World Health Organization (WHO) website:

www.who.int/csc/disease/avian_influenza/en/

The CDC website:

www.cdc.gov/flu/avian/index/htm

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Special thanks to:

Beijing United Family Hospital and Clinics

Tel: 6433-3960

Address: 2 Jiangtai Lu, Chaoyang District

Website: www.unitedfamilyhospitals.com