2 New H5N1 Thailand
Cases May Be
From ProMed
Source: Xinhua News Agency online
The 2 latest confirmed cases of human bird flu in Thailand might be [the result of] human-to-human transmission, a senior health official has said. Dr Charoen Chuchottaworn, an avian influenza expert at the Public Health Ministry's Department of Medical Services, said doctors concluded after reviewing the history of the past 2 cases that both victims presented very mild symptoms of avian influenza and neither had any physical contact with chickens or birds.
One of the victims was a boy in Bangkok and the other was an 18-year-old man from Nonthaburi province, The "Nation" newspaper reported on Fri 2 Dec 2005.
This left doctors no clues as to where the patients became infected with the H5N1 virus and showed that avian influenza had moved from causing severe human infection to milder cases.
Charoen, who is also a member of the National Committee issuing guidelines for the treatment of avian influenza, made the remarks on Thu 1 Dec 2005 at the Joint International Tropical Medicine Meeting 2005 in Bangkok. Dr Kamnuan Ungchusak, Director of the Epidemiology Bureau, challenged Charoen's assertion about human-to-human transmissions.
He told The Nation newspaper that while neither of the patients had direct contact with chickens, they lived in an environment where the virus was prevalent. "Chickens were dying near their homes and chicken droppings were everywhere around their neighborhood," he said. "They might have contracted the virus through contaminated soil."
Dr Charoen said the milder the symptoms, the harder it is for doctors to diagnose infection. This means that a lot more advanced laboratory facilities are needed with a testing technique called RT-PCR to confirm cases and decide if patients should be treated with the antiviral Tamiflu (oseltamivir phosphate). He said this meant that avian influenza could become asymptomatic now. The only tool [Tamiflu] available in Thailand to fight H5N1 infections at the moment is insufficient, he said. At present, Thailand has about one million capsules for 100 000 treatments of Tamiflu, but it is estimated that about 120 million capsules of the drug will be needed.
Only severe cases of human bird flu have previously been detected in Thailand simply because patients went to hospital for treatment. But doctors believe that there have been many cases with mild symptoms of the disease. "We believe that this is the tip of the iceberg," he said. Signs of possible human-to-human transmission were closely observed in Vietnam, where 10 clusters of probable human transmissions were detected in which the victims had no contact with infected poultry, Charoen said. Thailand and Indonesia had one official cluster, he said, but the Indonesian cluster showed clear-cut evidence because a child contracted H5N1 without going to an infected area, as her father had.
(No human cases of avian influenza had been reported from Thailand for more than one year before mid-October 2005. It is not clear from the text of this report whether the 2 cases described above are new cases or are 2 of the 4 cases previously described since mid-October. The mildness of the 2 cases described above may be significant, in that asymptomatic human cases could have gone undetected in the intervening period. This situation further emphasizes the need for comprehensive serological surveys of the general population in East Asian countries.
>From an analysis of a cluster of 3 cases in the same family in 2004, it was concluded previously that person-to-person transmission may have occurred in Thailand at an earlier phase of the outbreak. 2 family members (a mother and an aunt) appeared to have contracted infection from a critically ill index patient, but onward transmission was not observed (see: Avian influenza, human - East Asia (18): Thailand 20050124.0258).
The recent identification of 2 unrelated avian influenza cases without known contact with poultry may not be an indication of imminent widespread person-to-person transmission of avian influenza virus in Thailand. The alternative view is that there may be significant environmental contamination with virus where there are high numbers of poultry in the vicinity. The available information does not allow firm conclusions about the source of the virus. - Mods.MPP/CP)
Patricia A. Doyle, DVM, PhD Bus Admin, Tropical Agriculture Economics
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