Aug 4, 2006 (CIDRAP News) – A swan tested positive for H5N1 avian influenza at a German zoo yesterday, signaling the virus"e;s re-emergence in the country after a 3-month lull.

A black Australian swan at the Dresden Zoo in eastern Germany was found dead on Aug 1, but zoo officials weren"e;t too concerned at first because deaths in the breed are common, zoo biologist Ron Brockmann told Deutsche Presse-Agentur (DPA). But after the bird tested positive for H5N1 yesterday, he said, the zoo quarantined other animals and sought government permission to vaccinate the rest of the zoo"e;s collection of 720 birds of 112 species.

The swan was the first zoo animal infected in Germany, according to the story.  Brockmann said the virus might have entered the zoo last winter when wild birds visited the zoo"e;s ponds. The staff is worried that other animals in the zoo may become infected with the H5N1 virus if they eat dead birds, he said.

Germany"e;s last outbreaks of H5N1 avian flu were in February among wild birds and in April in farm poultry, Agence France-Presse reported today.

In other developments, a man in Vietnam who was hospitalized with possible avian flu tested negative yesterday, according to news services. The patient is from the southern province of Kien Giang, on the Cambodian border in the Mekong Delta. Vietnam hasn"e;t had a confirmed human H5N1 case since November 2005.

Three people in Thailand have also been cleared of H5N1 infection, according to the Bangkok Post. One is a 9-year-old girl from Lop Buri province in central Thailand who died 2 days ago. The other two patients—a 17-year-old boy and a 42-year-old woman—are from Chachoengsao province, east of Bangkok. The tests indicated that all three patients had a type A flu virus, but not H5N1, the newspaper said.

As of yesterday, the Thai Health Ministry reported that 97 patients from 24 provinces were under surveillance for possible avian flu. Those numbers were down from 164 patients in 21 provinces the previous day.

Thailand"e;s only confirmed human H5N1 case this year was in a 17-year-old boy from Phichit province who died of the disease Jul 24. A report in the Aug 3 Eurosurveillance Weekly suggests that the boy"e;s death indicates that poultry deaths in Thailand are being underreported. The authors observe that poultry deaths in the country were not reported until Jul 24, the day the boy died.

The boy"e;s case may be an example of a "sentinel human," meaning a human H5N1 case that triggers reporting of the disease in poultry, the report says.