Suspect cases of H5N1 in Kyoto, Japan

Kyodo (Japan) News is reporting suspected influenza H5N1 cases in five persons who had worked in February to cull 240,000 infected chickens and 20 million eggs on a Japanese farm near the town of Tamba in Kyoto Prefecture. The five had fever and tests showed the presence of antibodies against the virus in their blood, indicating a prior infection, but not the virus itself. None are reported in serious condition. They were among 60 farm employees, firefighters and government workers who worked on the operations. If confirmed (tests at the National Institute of Infections Diseases in Tokyo are continuing), these will be the first human cases of avian influenza in Japan.

At this time I have no information as to the protective measures taken by the four farm workers. The firefighter is reported to have taken the antiviral oseltamavir (tradename Tamiflu) prophylactically and to have worn a protective suit with hood, goggles and a mask. This kind of personal protective equipment needs to be fitted properly, and it would seem that if this is indeed a case of infection some breach occurred.

The fairly heavy exposures likely in this setting indicate that if disease transmission did in fact occur it does not signal the feared change in the virus that would make person to person transmission more likely. I have been following this case for a day or so, but it now appears to have made at least one wire service (Reuters Alertnet) so I thought I would post my take on it for those who follow the avian flu issue via this site.

Update 12/18/04: This story is now on the Asian wire services, although with little new information. Mainichi Interactive (Japan) reports that all the workers took antivirals and wore protective clothing and "surgical masks." These masks provide little protection. All the suspect cases are said to have recovered. Reading between the lines it sounds as if the symptoms may have occurred shortly after the cleaning in February and the government is only now releasing findings that these five individuals had antibody rises suggesting infection on retrospective analysis. Why this is being reported at this late date after exposure is unclear. I will only update this if there is something significant to say about it.

Added note, 12/18/04: China Daily confirms my suspicion that these were studies done in March and April of last spring. There are some additional details there for those who are interested. I will not report further on this unless there are significant new developments. Human infections from poultry are possible in a setting of heavy exposures.

Update/conclusion, 12/23/04: The Ministry of Health, Labour and Welfare of Japan is reporting the results of their investigation on their website (in Japanese). A rough translation has been made available by Dr. Akira Goto via ProMed-Mail. In essence, it reports that a serological investigation of 48 clean-up workers culling avian influenza infected chickens last February revealed five with antibodies to the Kyoto strain H5N1. For only one of the five was there a paired sample, so that is the only case classified as "confirmed." However the titers of four more workers make it highly likely they, too, were infected. Only one had symptoms (sore throat). None had fevers, as was earlier (erroneously) reported. This suggests that people may be asymptomatic for infection, which would be consistent with many other virus infections.