Just hours earlier, crowds had thronged past rows of squawking chickens, ducks and geese at a live-bird market in Camden County, New Jersey. But late last month, inspectors shut down the bustling market, ordering its complete disinfection after discovering an H5 avian influenza virus.

In the end, the virus turned out to be a strain that was not very harmful, but the event sheds light on what might happen if H5N1 is detected in the United States.

The country has weathered three major outbreaks of highly pathogenic bird flu before (see ‘Past US outbreaks’). ‘Low-pathogenic’ bird flu, which kills few infected birds, occurs far more regularly. In the latest case, New Jersey's agriculture department made a public announcement about the discovery of an avian-flu strain — but it left out salient details.

The announcement on 28 April did not mention when or specifically where the infection was detected, saying only that preliminary tests had marked it as negative for the neuraminidase protein N1. The statement did not mention the haemagglutinin protein; Nature learned later that the state had a faint positive for H5, which can occur in both high- and low-pathogenic strains. The first samples were tested on 21 April.

Discovery of avian flu led to the closure of a New Jersey live-poultry market. Credit: AP PHOTO/J. SZYMASZEK

Later confirmatory tests by the US Department of Agriculture (USDA) laboratory in Ames, Iowa, failed because technicians there could not grow the virus. In the meantime, other birds in the market had been killed and disposed of. The market was later reopened.

If a low-pathogenic strain of bird flu is discovered, then individual states, not the federal government, are responsible for alerting the public — and officials say this all went as planned. “The timeline was exactly as it should be,” claims Andrea Morgan, veterinary administrator for the USDA Animal and Plant Health Inspection Service. “The response that New Jersey launched was appropriate.”

But it was misleading, critics argue. Jody Lanard, a risk-communication specialist based in Princeton, New Jersey, has worked as a senior adviser in pandemic influenza communication to the World Health Organization. She notes that the state's two press releases omitted the fact that the strain was H5, focusing instead on the fact that it was not N1.

“They are afraid the public will hear H5 and go nuts — a case of official panic about panic,” she says. “If they really think the public is that fragile, they might be tempted to hold back lots of preliminary information, and delay issuing material when it really matters.”

Karen Eggert, a spokeswoman for the USDA, says the department is still working out how and when it would alert the public to outbreaks of highly pathogenic strains such as H5N1. In the interests of openness, officials are considering announcing it immediately after the first confirmatory molecular tests.