A history of the Avian Influenza A/H5N1 strain

Editor’s note: In February 2005 I received at the Effect Measure blog a lengthy history of the H5N1 problem, penned by someone who identified himself as “Dylan” (a pen name). Below is only the first part of what he sent. This was before many other people were paying much attention to bird flu, but Dylan had obviously been keeping careful track for some time, another example of the fine talent that’s out there. The Wiki is a way to build on, correct and extend what Dylan started so capably. This is an open invitation to do so.

People’s Republic of China, 1996

The Asian form of H5N1 was first detected in domestic geese in southern China in 1996. Other forms of H5N1 had appeared in chickens, in Scotland, for instance, as far back as 1959.

Hong Kong, 1997

The Asian form of H5N1 infected eighteen people in Hong Kong, in 1997. Of eighteen people, six succumbed as a result of the infection. This was the first time that H5N1 was shown to infect human beings. The Hong Kong virus was identified as H5N1, at that time, and every chicken in Hong Kong – nearly one-and-a-half-million of them – was culled. Then, the pathogen disappeared. And many experts believed that an influenza pandemic may have been prevented, as a result. Then H5N1 seemed to go underground, although in reality it remained “airborne,” since its natural reservoir appears to be migratory aquatic birds.

Hong Kong, 2002

It surfaced again in 2002, and again it showed up in Hong Kong, again infecting chickens. This time there were no human victims. Why would something like H5N1 show up in Hong Kong … and nowhere else? Twice … in five years? Because Hong Kong is geographically contiguous with China’s southern Guangdong Province, and gets most of its live poultry and pigs from there. China is secretive – and paranoid – about health issues (it wasn’t until after other cases began to appear in different geographical locations that China finally confessed that SARS had begun in Guangdong province).

Southeast and East Asia, 2003—early 2004

Then, in early 2003, a father and his nine-year-old son, who had been visiting relatives in Fujian Province in China, were hospitalized when they returned to Hong Kong with H5N1 infection. A second of the father’s children – an eight-year-old girl – had died of an undiagnosed respiratory illness, while visiting in China. There was no autopsy or diagnostic testing. The father subsequently succumbed, the hospitalized boy recovered. The virus responsible was found to be a mutated strain of the H5N1 virus that had first surfaced in human beings in Hong Kong, in 1997.(This event preceded the first known cluster of probable human-to-human transmission that transpired in Thailand in 2004 between three family members. The daughter was the index case, and her mother and an aunt who tended to her in the latest stages of her illness were subsequently infected; the aunt survived, and the mother died. The infection/death sequences among the members of the family from Hong Kong probably followed a nearly identical pattern as that of the Thailand cluster, with the daughter being infected and succumbing to the disease before her father and her brother expressed symptoms, and were later hospitalized in Hong Kong. The similarities between the two clusters suggest, to me, that the first true case of human-to-human transmission – although unrecognized as such – was the Feb. 2003 cluster from Fujian Province. We’ll never know, for certain, because the girl’s body was disposed of.)

In December of 2003, H5N1 appeared, for the first time, among domestic bird flocks on farms in South Korea. Shortly after it appeared in Japan, China, Vietnam, Thailand, Laos, Indonesia, and Malaysia. H5N1 had never been identified in most of these countries before. It was rapidly expanding over a very broad geographical region encompassing nearly all of Southeast Asia.

Other appearances, in people, apparently had preceded the Korean event, but were not recognized at the time. Between the end of October, and the end of December 2003, six children were admitted to a hospital in Hanoi, Vietnam, with upper respiratory infections. All six subsequently died, but the pathogen initially went unidentified. On January 5, 2004 Vietnam informed the World Health Organization that eleven previously healthy children (including the six mentioned above) had been admitted to a hospital in Hanoi with severe respiratory illness. Seven of the eleven subsequently died. Then a twelfth child, in a provincial hospital, also succumbed to a respiratory infection. Thus the mortality was extremely high (eight of twelve). On January 6, 2004, WHO was informed of suspicious chicken deaths in southern Vietnam. By January 8, Vietnam informed WHO that birds on three farms, in two of its southern provinces, were infected with H5N1. 70,000 birds died or were destroyed to prevent the spread of the disease. But on January 11, Vietnam advised WHO that another child, and the first adult, had been admitted to a hospital in Hanoi, with what appeared to be the same respiratory infection previously reported. On the same day, Hong Kong’s National Influenza Center announced that tests on two samples from two fatal cases of respiratory infections in Vietnam proved positive for the H5N1 virus. It was back and it was infecting human beings, again.

Dylan’s account has now brought us up to the midwinter months of 2004..

Flocks of domestic birds now began to die in huge numbers all over Southeast Asia. The US embargoed all imports of live birds and any sort of bird products from anywhere in Southeast Asia (with the single exception of Hong Kong). Eventually, somewhere between one-hundred-million, and one-hundred-twenty-million domestic birds (mostly chickens) were either killed by the pathogen, or culled throughout Southeast Asia. By February 2004, China reported that H5N1 had been confirmed in 10 of its 31 provinces and Vietnam reported 52 of its 64 provinces showed H5N1 activity in domestic birds. H5N1 had now becoming endemic in Southeast Asia, and eradicating it became virtually impossible.

Thailand now also reported human cases. In late spring and early summer of 2004, the epidemic subsided but reappeared just a few months later, infecting human beings, again. By the end of October 2004, H5N1 had hospitalized a total of 44 people in Thailand and Vietnam. Thirty-two died. All cases were clinically confirmed by WHO.

But birds and humans weren’t the only species affected. In an exotic tiger breeding zoo in Bangkok, tigers that had been fed slaughtered chickens began to sicken and die. Of roughly four-hundred tigers in the zoo, slightly more than a hundred either died of the disease or were culled. Domestic cats in Thailand were found to be infected and a leopard in another Bangkok zoo, the first known flu infections of any sort among felines.

In November 2004 a Chinese virologist at a conference in Beijing announced that pigs on several farms in at least one province in China had tested positive for H5N1 (Guangdong? Fujian?), but the Chinese government later denied this claim. And in mid-October, a Thai national (thought to be a drug smuggler) was stopped in the Brussels, Belgium airport. His carry-on luggage contained two exotic miniature eagles, secured in plastic tubes. The birds, only barely alive, tested positive for H5N1.

In November the WHO announced that domestic ducks in Southeast Asia are likely to be a huge, silent reservoir for the pathogen. This was an entirely new, unexpected, and disturbing finding. The ducks were symptom free but they shed the virus in feces, saliva, and mucosal secretions for a period of seventeen days, after they are infected. And they roamed everywhere, unrestrained, in practically every village in Asia, swimming in the ponds and lakes that nearly every creature around them uses for their water supply.

The WHO provides a thorough history of the H5N1 virus in its January 2005 report
Avian influenza: Assessing the pandemic threat · pdf

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Page last modified on April 09, 2006, at 03:36 AM by cassandra