Thu, Feb 12, 2009 - Page 8 News List

A bird flu epidemic in the making

By Mayo Kuo , Max Kuo 郭明裕 郭明實

Since last month, eight people are known to have been infected with the H5N1 strain of the avian influenza virus, of whom five have died. Strangely, the UN Food and Agriculture Organization has received no reports of H5N1 infection in birds from the Chinese Ministry of Agriculture. It could be that the Chinese government is hiding information about infections among poultry.

If that is the case, sporadic cases of people infected with bird flu in various provinces of China may only be the tip of the iceberg.

Since children of poultry raisers are most susceptible to bird flu infection and the death rate for avian influenza is more than 50 percent, failure to divulge the true situation would hamper preventive efforts and put children’s lives at risk.

Recently, 21 dead birds were found washed ashore on Hong Kong’s Lantau Island. The birds were believed to have come from the Pearl River Delta — the origin of H5N1 avian influenza — which has the highest density of poultry farming in the world.

The fact that three of the birds have tested positive for H5N1 tends to confirm suspicions that China is hiding information about bird flu cases.

In 2005, Jeffery Taubenberger, chair of the Department of Molecular Pathology at the US Armed Forces Institute of Pathology, published the genome of the 1918 pandemic strain of H1N1 in the scientific journal Nature. The strain was confirmed to be a genetic mutation of an avian influenza virus that crossed over into humans and spread rapidly, and was 50 times to 39,000 times more toxic than the original strain.

The following year, Taubenberger published a chart showing mass deaths of birds infected with the avian influenza virus in 1916 in Emerging Infectious Diseases, a journal of the US Centers for Disease Control and Prevention.

Considering this historical pattern, the appearance of dead birds on the shore of Lantau Island should be taken as a serious warning.

The influenza epidemic of 1918 coincided with the end of World War I.

Last year saw a string of disasters in China — blizzards, the Sichuan earthquake and a drought in its northern provinces. Could it be that natural and man-made calamities are setting the scene for a bird flu epidemic?

Another cause for concern is that outbreaks of new strains of human influenza have occurred in cycles, at intervals of between 10 and 40 years.

If this pattern is any indication, another outbreak could be expected soon.

Up until now, H5N1 bird flu has infected mainly children and young people under 20 years old. Figures published by the US magazine Annals of Internal Medicine in 1987 show that, among all historical outbreaks of new flu strains, only in the 1918 human H5N1 flu pandemic were the majority of those infected adults aged between 20 and 40.

Other human flu outbreaks have affected mostly elderly people aged 65 and above.

If H1N1 infection among humans starts moving into the 20 to 40-year-old age group, the alarm bells should start ringing.

Experts at the US CDC think that if mortality among those infected with H5N1 falls below 2.5 percent and the infection rate rises over 25 percent, it will show that the H5N1 virus has shifted from attacking α2,3 sialic acid-containing receptors in the lower respiratory tract — as discovered by Mikhail Matrosovich and others in 2005 — to new infection sites in the upper respiratory tract, from where, after replicating itself in vast numbers, it can spread easily via airborne droplets. This would make the virus more infectious.

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