U.S. farm and health officials are racing to assess the threat that a type of bird flu never before seen in the country poses to humans and poultry, employing emergency plans drawn up in the wake of a devastating outbreak in birds last year.

The federal government sprang into action on Friday after confirmation overnight that the virus had hit an Indiana turkey farm, alerting other states to the danger and putting workers who might have been exposed to the virus under surveillance.

Last year's outbreak led to the deaths of more than 48 million chickens and turkeys, either killed by the virus or culled to contain it. No cases were reported in humans.

Strains similar to the new virus, known as H7N8, have on rare occasions made people ill and the U.S. Department of Agriculture (USDA), U.S. Centers for Disease Control and Prevention (CDC) and state officials aim to reduce the risk of human infection.

They also want to blunt the impact on the poultry industry, which suffered billions of dollars in losses in last year's outbreak. Egg supplies shrank and prices surged to record highs.

"We are hopeful that as we respond very quickly to this virus that we can get it contained and hopefully not see an extensive outbreak like we did last year," said T.J. Myers, an associate deputy administrator for the USDA's Animal and Plant Health Inspection Service.

Even if the response is fast, the government's ability to contain the disease is far from certain. Officials have never dealt with this strain before, and wild birds are thought to spread the disease to farms through feces dropped from the air, making infections difficult to prevent.

U.S. officials have taken to heart lessons from last year's outbreak, when USDA workers could not always kill infected flocks fast enough to contain the virus. Workers are now trying to cull sick flocks within 24 hours of diagnoses, following a goal the agency set in the autumn.

Most turkeys at the infected farm were killed within a day, but it was 29 hours before all were dead, said Denise Derrer, spokeswoman for the Indiana State Board of Animal Health.

No human infections associated with the new strain have ever been reported, according to the USDA.

Still, people who interacted with infected turkeys were quickly placed under a new monitoring plan developed in response to last year's outbreak, Michael Jhung, a medical officer at the CDC, told Reuters. The agency also plans to conduct lab tests and animal studies of the virus.

Similar H7 viruses - which share the same surface proteins - have caused problems in people ranging from mild, flu-like symptoms to serious respiratory illness, Jhung said.

"We know very little about this particular virus because we haven't seen it, but we want to take as many precautions as we can to prevent any human infections," he said.

There is always uncertainty around any new strain of influenza because the virus acquires mutations passing from host to host.

The Indiana flock appears to have become infected when a less dangerous form of the virus in the area mutated, said John Clifford, the USDA's chief veterinarian.

Limited genetic data from preliminary diagnostic tests last week showed this H7N8 virus originated from North America, while last year's strains had roots in Europe and Asia, government officials said.

North American viruses have typically posed less of a threat to humans than viruses from the Asian Avian H5N1 lineage, said Carol Cardona, an avian flu expert at the University of Minnesota.

Viruses in the H5N1 lineage "are super bad guys," Cardona said. Still, outbreaks of North American viruses in Pennsylvania in 1983 and British Columbia in 2000 were "devastating and difficult" for poultry, she added.

The new strain found in the United States, like these previous viruses, is considered highly pathogenic, meaning it is especially deadly to poultry.

In Indiana, the USDA quickly deployed personnel and equipment to assist the state with culling birds and testing nearby flocks, said Bret Marsh, Indiana's state veterinarian.

Marsh alerted other states about the new virus outbreak on an emergency conference call in the early hours on Friday.

"We realize that if it's indeed of wild bird origin, they know no boundaries so we want to make sure that everyone is properly informed," Marsh told reporters.

Bird flu cost the U.S. poultry industry an estimated $3.3 billion in 2015 as farmers had to destroy infected flocks and halt production for months. Importers also cut back on trade in the $5.7 billion poultry and egg export market, and some have already limited shipments because of this new outbreak.

U.S. negotiators have worked with trading partners in the past year to focus restrictions on infected counties or states, instead of blocking shipments from the entire country, said Toby Moore, spokesman for the USA Poultry & Egg Export Council. That could minimize the economic burden of outbreaks.

Farmers also have strengthened cleaning and security practices in a bid to keep out the virus, with many requiring workers to change their shoes before entering barns and barring delivery trucks from getting too close to poultry houses.

"In the poultry business, there's a positive determination that this new strain not have any chance at proving what it might be able to do," said Keith Williams, a spokesman for the National Turkey Federation, a trade group.