BEIJING – A sixth person has died from the H7N9 strain of bird flu in China, prompting officials there to step up its response to the deadly virus.

News reports state that Chinese officials are advising people to avoid live poultry. Virologists have been sent to chicken farms across China, and more than 20,000 birds were slaughtered at a Shanghai market where a pigeon tested positive for the virus. The H7N9 virus is considered a low pathogenic strain that isn't easily contracted by humans, and no human-to-human transmission has been confirmed.

But public health organizations around the world are concerned that the H7N9 virus could mutate and start a pandemic. The virus has killed six of the 14 people confirmed to have the virus. Also, the virus seems to spread through poultry flocks causing no visible signs of illness, according to the United Nation’s Food and Agriculture Organization.

"Unlike H5N1, where chickens were dying off on a large scale, with this virus we don't have a red flag that immediately signals an infection. This means farmers may not be aware that virus is circulating in their flock. Biosecurity and hygiene measures will help people protect themselves from virus circulating in seemingly healthy birds or other animals," said Juan Lubroth, FAO chief Veterinary Officer.

Lubroth said good biosecurity measures are even more essential to reducing the risk of virus transmission to humans and animals.

“Good biosecurity and hygiene measures implemented by farmers, livestock producers, transporters, market workers and consumers represent the first and most effective way to protect the food chain,” he said.

Atlanta-based Centers for Disease Control said on its web site that the agency is monitoring the situation in China and coordinating with domestic and international counterparts to gather more information about the virus. The agency is also ready to help develop a candidate vaccine virus.