Jakarta, June 14 : The recent spike in the number of Covid-19 cases in Indonesia's Kudus district of Central Java province is due to the highly infectious Delta variant of the virus, an official said. Central Java Governor Ganjar Pranowo said on Sunday that 86.11 per cent or 62 out of a total of the 72 cases in Kudus emanated from the Delta variant, reports Xinhua news agency. "The spread of this virus variant is very fast. Three weeks ago Covid-19 in Kudus affected only three sub-districts but today they are happening in 11 sub-districts," Pranowo said. "Kudus experienced a significant increase in positive cases in a week, jumping more than 30 times from 26 to 929 cases," Wiku Adisasmito, the national Covid-19 task force spokesperson, said. Kudus has so far recorded 10,525 confirmed cases, with 7,322 recoveries and 861 deaths. Health Minister Budi Gunadi Sadikin said the Delta variant in Kudus came from Indonesian migrant workers who returned from India. "We have been taking good care of airports and seaports in Indonesia," said the Minister. /IANS