People are seen at a quarantine center in Kolkata, India on April 18, 2020. India's Health Ministry said on Sunday morning that the death toll due to COVID-19 rose to 507 and the total number of confirmed cases reached 15,712. (Str/Xinhua)

A woman is seen at a quarantine center in Kolkata, India on April 18, 2020. India's Health Ministry said on Sunday morning that the death toll due to COVID-19 rose to 507 and the total number of confirmed cases reached 15,712. (Str/Xinhua)

People are seen at a quarantine center in Kolkata, India on April 18, 2020. India's Health Ministry said on Sunday morning that the death toll due to COVID-19 rose to 507 and the total number of confirmed cases reached 15,712. (Str/Xinhua)

A dog is seen on an empty road during the nationwide lockdown in Kolkata, India on April 18, 2020. India's Health Ministry said on Sunday morning that the death toll due to COVID-19 rose to 507 and the total number of confirmed cases reached 15,712. (Str/Xinhua)

People are seen at a quarantine center in Kolkata, India on April 18, 2020. India's Health Ministry said on Sunday morning that the death toll due to COVID-19 rose to 507 and the total number of confirmed cases reached 15,712. (Str/Xinhua)