DEERFIELD, Ill. – The discovery that a flock in Arkansas has been exposed to avian influenza has raised questions about the virus and what the risks are to people.

In this week’s case, 15,000 hens at a Tyson Foods Inc. contract supplier were culled after routine testing found the chickens had antibodies for H7N3, a low pathogenic strain of the virus. Both the company and government officials have taken action to depopulate and bury the chickens.

This is the first incident since July 2007 when another low pathogenic strain was found in about 54,000 turkeys in Virginia. All of those involved have said there is no risk to humans. The pathogenicity of a strain is determined by the severity of the illness caused.

Gary Mickelson, spokesman for Tyson, said that the flock tested positive for antibodies of the virus, but not the virus itself. There was no indication that any of the birds had virus when they were destroyed earlier this week and none of the hens had active infections.

Both Tyson and Arkansas state officials have stepped up the monitoring of flocks in the area to ensure there was no spread of the virus. Mickelson said that the company will be testing all breeder farms that serve the Tyson poultry complex in northwest Arkansas, which is addition to an existing program where all chickens are tested before moving on to processing.

The state is testing facilities within six miles of the affected farm. Tyson, as an additional measure, is testing facilities up to ten miles away from the farm.

According to Rachel Iadicicco, spokeswoman for the Animal and Plant Health Inspection Service (APHIS), it is policy to depopulate any flock that has indications of H5 or H7 subtypes of the bird flu. This is done to ensure that the virus does not have a chance to adapt or mutate into a form that can be infectious to humans.

“This is a standard policy,” she told ProvisionerOnline. “A lot of the routine testing is done to eradicate it to prevent mutation. This shows the system is working. It prevents a larger problem from occurring in future.”

The discovery has meant that poultry from Arkansas is no longer being exported to markets in Russia and Japan. Iadicicco said that this is because of existing bilateral agreements with both countries. The United States is required to notify the countries of any finding of H5 or H7 subtypes. It also means that exports are self-suspended for 90 days. Both countries have historically had very strict controls on imported food products.

Humans can be infected with strains of bird flu. However, most people who are infected with bird flu are those who are in direct contact with contaminated environments. In the case of H7N3, according to the Centers of Disease Control, the last time there were human were infected with the virus was in 2004 in Canada. Both were poultry workers who recovered fully. Most forms of the flu that humans get come from mammals such as pigs, dogs and horses. The agency also says the infections are rarely transmitted between humans.

Madelaine Fletcher, a public affairs specialist with APHIS, said that her agency has been doing outreach to educate people on how to prevent bird flu infections in poultry for the past four years. She says the agency talks to people, both in the industry and hobby poultry raisers, about biosecurity.

“Essentially, what we say is look for signs of illness, stick to good hygiene rules and buy birds from a reputable dealer,” she said.

Warning signs of an infection include sudden death without clinical signs; lack of energy and appetite; decreased egg production; soft-shelled or misshapen eggs; swelling of the head, eyelids, comb, wattles, and hocks; purple discoloration of the wattles, combs, and legs; nasal discharge; coughing, sneezing; lack of coordination; and diarrhea. APHIS says that birds with a low pathogenic strain may not show symptoms at all.

Fletcher said that it is important to take action immediately if there are suspicions that a flock is sick. The local veterinarian, farm extension agent, state veterinarian or the federal veterinarian for the area should be contacted. People can call the U.S. Department of Agriculture in such a situation at (800) 536-7593.

The USDA says that the following steps can help prevent infection:

• Keeping distance from poultry and restricting access to the birds.
• Keeping the area clean.
• Washing before coming into contact with birds, especially if there has been contact with other flocks.

Fletcher said that commercial poultry producers are aware of good biosecurity for flocks.

“It can pose a risk,” said Fletcher. “It’s certainly something that can spread. Take those precautions for yourself and your neighbors.”