5 MIN. DE LECTURA
* Minnesota is second U.S. state to declare emergency over bird flu
* State recommends antiviral drugs for exposed farm workers
* Could call out national guard if needed
* Risk of human infection seen low - health authorities
* National Guard will be called up if needed - Minnesota governor (Adds details of outbreak, Minnesota governor comments)
By P.J. Huffstutter
CHICAGO, April 23 (Reuters) - Minnesota declared a state of emergency on Thursday over a fast-spreading strain of avian flu that has led to the extermination of more than 7.3 million birds in the country. It followed Wisconsin's action on Monday.
The highly pathogenic H5N2 strain of bird flu has been identified on 46 Minnesota farms in 16 counties and affected more than 2.6 million birds in the state.
State health officials said they were expediting prescriptions for the antiviral drug Tamiflu for farm workers and others who have been in direct contact with infected flocks. No human infections have been reported in this outbreak.
"There's no reason for anybody in the state of Minnesota to be concerned about their own health," Governor Mark Dayton said at a press conference on Thursday after declaring the state of emergency.
Federal and local public health authorities have said the risk of human infection is low.
The state's action to provide antiviral drugs follows recommendations from the U.S. Centers for Disease Control and Prevention (CDC).
Minnesota's health department approached 140 farm workers and others who had been in direct contact with infected birds and advised 87 of them to take the Roche antiviral medication as a preventative measure, the department's spokesman Michael Schommer said. Seventy of them took the drug, he said.
Of the 62 people that state health officials have followed up with so far, none have been infected by the virus, Schommer said.
The virus can kill nearly an entire infected flock within 48 hours. Millions of turkeys and chickens are in quarantine waiting to be culled and large flocks have already been destroyed.
Officials have said they believe wild birds are spreading the virus but they do not know how it is entering barns.
Two bird flu strains have been discovered in the United States this year. The H5N2 strain is in Arkansas, Idaho, Iowa, Kansas, Minnesota, Missouri, Montana, North Dakota, Oregon, South Dakota, Washington and Wisconsin. It has also been identified on farms in Ontario, Canada.
The H5N8 strain has been identified in California and also in Idaho, U.S. Department of Agriculture data showed.
Iowa, the top U.S. egg-producing state, said on Monday that a lethal strain of bird flu had been found in hens at an egg-laying facility near the city of Harris run by Sunrise Farms, an affiliate of Sonstegard Foods Company. The company said the facility houses 3.8 million hens.
"We went to great lengths to prevent our birds from contracting AI (avian influenza), but despite best efforts we now confirm many of our birds are testing positive," Sonstegard said.
Hormel Foods Corp, based in Minnesota, said this week that the virulent strain of avian influenza may drag its fiscal 2015 earnings toward the lower end of forecasts.
The virus has been identified at a facility west of Minneapolis that is owned by a subsidiary of Hormel. Minnesota is the largest turkey-producing state in the country.
Minnesota's Dayton said he had authorized the National Guard to be called up for duty if needed.
In Wisconsin on Monday, Governor Scott Walker declared a state of emergency after three poultry flocks became infected in the past week, his office said. A state spokeswoman said guardsmen would disinfect trucks exiting infected facilities.
In Minnesota, researchers are investigating the virus' spread, testing animal feed and conducting experiments to see if the virus is being carried onto farms by windborne dirt, dust or feathers, state officials said on Thursday.
The CDC said on Wednesday that H5N2 is genetically different from the H5N1 bird flu virus that has spread from birds to humans in the past.
On Tuesday, Mexico, the biggest buyer of U.S. chicken, halted imports of live birds and eggs from Iowa. (Reporting By P.J. Huffstutter. Additional reporting by Julie Steenhuysen.; Editing by Bernard Orr, Toni Reinhold)