U.S. officials have reported a second case of bird flu on another farm in the state of Delaware, prompting the killing of 72,000 chickens and the quarantining of 80 farms in the region, Associated Press reports.

The first outbreak of bird flu in the state was reported Friday.  The Delaware strain, known as H7, cannot be passed on to humans, but it has caused seven nations —  China, Poland, Japan, Malaysia, Singapore, South Korea and Brazil — to ban at least some poultry imports from the United States, the world's second-largest exporter of chickens.

The second case of the disease in the United States was found in a commercial flock of roaster-type chickens, belonging to the company Perdue Farms. The flock was believed to have been infected by a nearby flock of chickens that was raised for the New York City live markets, the company said (Gretchen Parker, AP/Boston Globe, Feb. 11).

Meanwhile, the World Health Organization has warned that it would take time for the Asian nations affected by bird flu to be able to control the disease.

"We are probably looking at six months to two years before some of these outbreaks can be brought under total control in the poultry population," said Mike Ryan, the WHO's global response coordinator for avian flu.

So far, at least 19 people have died from the disease in eight Asian countries.

According to CNN.com, WHO is currently uncertain on whether the avian virus cannot be passed between humans (Feb. 10).

Yesterday, the agency said it is running more tests on the two Vietnamese sisters who died last month to ensure the bird flu virus cannot be passed from person to person.

WHO also said it is possible that there may be human cases of the virus in China, although none have been reported (U.N. Wire, Feb. 10).

Despite the statement, China Radio International reported today that the organization said it is satisfied with the Chinese government for taking urgent measures to kill infected birds to avoid human infection (People's Daily, Feb. 11).

But Harvard University Medical School instructor Henry Niman said he is skeptical there are no human cases in China, where 14 out of 31 provinces have confirmed or suspected outbreaks of bird flu.

"It seems they've got the virus widespread and it's been around for some time," Niman said.  "That leads me to believe there's more going on in China" (CNN.com).