PATNA, March 9 -- Fresh cases of H5N1 avian influenza, commonly known as bird flu, have been detected in crows in Bihar's Bhagalpur and Purnia districts, taking the total number of affected districts in the state to six, officials of the dairy, fisheries and animal resources department said on Sunday. The latest cases were reported from Sultanganj block in Bhagalpur and Banmankhi in Purnia after around 50 crows were found dead in the two districts. "We had sent samples of the dead crows to the Regional Disease Diagnostic Laboratory (RDDL) in Kolkata over a fortnight ago. The laboratory confirmed the presence of the H5N1 virus on Saturday," an official of the department said. Sultanganj is the second block in Bhagalpur to report bird flu. Around 22 crows had died there over the past fortnight, prompting authorities to send samples for testing. Earlier, Naugachhia block in the district had reported the virus after around 70 crow deaths last month. Purnia is the latest addition to the list of affected districts after the RDDL confirmed the presence of H5N1 in samples from Banmankhi, where 26 crows had died over a fortnight ago, officials familiar with the matter said. Officials said that as part of the containment protocol, they will undertake intensive fogging and sanitisation drives within a 1-km radius of the affected areas using antiviral agents and disinfectants such as sodium hypochlorite and glutaraldehyde. So far, Darbhanga, Bhagalpur, Katihar, Patna and Bettiah in West Champaran have reported more than 400 crow deaths since January 28, when the first bird flu death in the state this year was reported in a crow. The virus was first detected this year in crows from Patna's Kankerbagh J-sector locality and near the high court area. The infection later spread to poultry birds, leading to the culling of around 5,000 birds at the poultry research and training centre under Bihar Animal Sciences University in Kaushal Nagar in Patna's Chitkohra locality on February 25. Officials said the department is closely monitoring the possible spread of the virus among poultry birds in the state capital. Meanwhile, the state government lifted the ban on visitors to the Sanjay Gandhi Biological Park, popularly known as Patna zoo, beginning Sunday. The zoo had remained closed from February 27 to March 7 as a precautionary measure. A section near the zoo's giraffe enclosure falls within a 1-km radius of the epicentre of bird deaths at the poultry research and training centre, prompting authorities to enforce preventive measures....