China Reports a Human Case of Rare H10N3 Bird Flu

A 41-year-old man in China’s eastern Jiangsu Province is the first known human to be infected with a strain of bird flu known as H10N3, China’s National Health Commission said on Tuesday — a development that experts said merited close monitoring because of an underlying continued risk of pandemic flus.

Avian viruses do not typically spread among humans, but they can pose a danger to humans if they mix with a human virus, said Raina MacIntyre, the head of the biosecurity program at the Kirby Institute at the University of New South Wales in Australia.

“If someone has human flu and is infected with bird flu, the two viruses can swap genetic material,” she said. “That’s why you see the concern for pandemic flu arising in countries where humans and livestock have very close contact.”

The Health Commission’s announcement said that there was no evidence of human-to-human transmission in the Jiangsu case. Contact tracing and surveillance have not uncovered any other infections, officials said.

Influenza viruses differ from coronaviruses, and the World Health Organization is working with the Chinese government to monitor the case, according to a statement from the W.H.O. division in Beijing.

The man began feeling feverish at the end of April and was hospitalized on April 28, the Chinese government statement said. On May 28, genome sequencing by the Chinese Center for Disease Control and Prevention determined that he had been infected with H10N3.

The government announcement did not say how the man had been infected, and the W.H.O. said the source of infection was still unknown. The man’s condition has stabilized, and he is ready to be discharged, the government said.

Professor MacIntyre said that people who are usually infected by avian viruses are those who are in prolonged close contact with the birds, such as poultry handlers.

The W.H.O. said that H10N3 had “been detected periodically in birds in live bird markets as early as 2002,” but the virus is unlikely to kill birds or lead to many signs of illness.

“As long as avian influenza viruses circulate in poultry,” the organization said, “sporadic infection of avian influenza in humans is not surprising, which is a vivid reminder that the threat of an influenza pandemic is persistent.”