NEW DELHI : The spread of avian influenza, commonly known as bird flu, in four Indian states has posed a fresh challenge before the country that is already struggling to tackle the covid-19 pandemic.The government on Wednesday said while the infection has not yet been reported in humans in India, the disease is zoonotic, and the secondary spread by human handling (through fomites) cannot be ruled out. Also Read | The race to take fashion retail onlineIn India, bird flu spreads mainly from migratory birds coming into the country during between September-October and February-March.Avian influenza has been reported from 12 epicentres in four states.