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 the Maharashtra government announced a week-long lockdown - from March 15 to March 21 - in Nagpur, which reported over 1,800 cases in 24 hours. Six states - Maharashtra, Kerala, Punjab, Karnataka, Gujarat and Tamil Nadu - have been reporting over 85 percent of total cases for the last few days.