Nashik: Bird flu infection continues to spread in Navapur, with samples from two more poultry farms testing positive, prompting authorities to launch a fresh bird culling drive and expand surveillance beyond the already identified epicentres.Dr Sanjay Khachane, District Deputy Commissioner of Animal Husbandry Department, said the latest investigation indicated that the infection has spread outside the earlier prohibited areas.“The department had conducted surveillance of poultry farms beyond the centre, which included two different poultry farms. Samples from them were sent to the laboratory, where samples from two farms in different areas were found positive. This is the third group of farms, and both farms extend beyond the infected areas surrounding the first farms. This means the infection is still increasing,” he said.The authorities have now declared both the farms as new centers and have started re-survey of poultry units in the surrounding areas. Birds within the affected perimeter will be culled to prevent the spread.“Currently, the number of birds killed in both the farms is around 50,000. The survey will establish the exact number of birds killed in the farms,” ​​Khachane said.In the first outbreak, birds were culled at nine farms in the three epicentres. In the second phase, four farms from three epicenters were affected. In the latest instance, two new epicenters have emerged, indicating that the infection has spread beyond a 1 km radius of previously affected areas.Around 3.9 lakh birds have been culled so far, while 21.6 lakh eggs and 4.99 lakh tonnes of fodder have been destroyed by the rapid reaction teams engaged in containment efforts. The latest campaign to cull birds at newly identified farms will begin on Thursday as part of intensified measures to control the outbreak, officials said.Despite decline, Navapur remains an important food artery. Currently about 12 lakh layer birds lay an estimated 10 lakh eggs every day.