The Centre is "very worried" about the upsurge in coronavirus cases in Maharashtra, NITI Aayog member Dr VK Paul said on Thursday, adding the virus cannot be taken for granted if the country has to remain Covid-free. The remark comes on a day when Chief Minister Uddhav Thackeray announced a week-long lockdown - from March 15 to March 21 - in Nagpur, which reported over 1800 cases in a day. "We are very worried about Maharashtra. This is a serious matter. This has two lessons - don't take the virus for granted, and if we have to remain Covid free, then, we need to follow Covid-appropriate behaviour," he said, while addressing a press conference.