A low-risk strain of bird flu virus has been found at four live chicken markets in the US state of New Jersey, days after outbreaks in Delaware led to the killings of tens of thousands of birds, local newspaper reported Thursday.

The virus detected in New Jersey is called H7N2, the same as the one discovered last week in a farm in Kent County, Delaware. A second farm in Delaware's Sussex County was confirmed to be infected by H7 bird flu on Tuesday, but test results of the exact virus subtype are not immediately available.

The H7N2 virus is not a great concern to humans, although there is some risk of it mutating into a more pathogenic form, Clifton Lacy, commissioner of New Jersey's state Department of Health and Senior Services, told The Star-Ledger, a local newspaper in the state.

The findings are not unusual, state officials stressed, saying the virus has been present in live poultry markets in New York and New Jersey for many years.

"Our theory is those live markets in northern New Jersey and New York City keep it circulating," Richard Lobb at the National Chicken Council, which represents the country's largest poultry producers, was quoted by the newspaper as saying.

New Jersey tested the live chicken markets in late January, as it typically does every winter. Results are in for about half of the state's 35 markets, with four markets confirmed positive to the virus.

The state typically finds bird flu at about 40 percent of the live chicken markets, despite strict controls designed to prevent the virus from reaching them, said Nancy Halpern, the state veterinarian.

It is likely at least one bird was infected at each of the four markets, though the virus also might have been found on cages, said Halpern, who would not identify which market has been infected.

Following the findings of bird flu at the two farms, officials in Delaware have destroyed more than 80,000 chickens and quarantined about 80 farms within six-mile (10-km) radius of the infected spots.

The bird flu outbreaks in Delaware have prompted a growing number of countries to ban US poultry imports.

US chicken producers export more than 15 percent of their birds annually for more than a billion dollars in revenue.

(Xinhua News Agency February 13, 2004)