Czech authorities decided Thursday to slaughter 68,000 healthy poultry in three commercial farms near the latest two H5N1 occurrences in an attempt to halt the spread of the bird flu in the area, said Josef Duben, a spokesman for the state veterinarians, according to dpa. The three broiler chicken and turkey farms lie within three kilometres of the farms, in eastern Bohemia, where the H5N1 bird flu strain, known to be deadly to humans, was confirmed Wednesday. Since June the virus hads been detected at four farms in the vicinity, all of which belong to the same owner, Duben said. Based on the character of the breeds the veterinarians now believe that the disease has spread from the location of the first outbreak to the other farms. "It is very likely that it has spread from the first focus to the second one and so on," Duben told Deutsche Presse-Agentur dpa. "It is so close that it would presumably break out there as well." Teams of veterinarians and soldiers were culling some 71,000 hens, in which the H5N1 strain was confirmed Wednesday, as well as the poultry raised by residents within a radius of three kilometres. This year, the dangerous strain was also found in a dead swan in the country's south. Last year, the potentially lethal strain was found in 14 dead swans in the country's southern regions. The disease was also recently detected in wild and domestic birds in Germany and France. Some 190 people around the world have died of bird flu since 2003, mainly through coming into close contact with infected poultry, according to the World Health Organization (WHO). Scientists fear the virus could mutate into a form easily transmissible between humans, which could touch off a global pandemic that would kill millions of people.