India, Nov. 27 -- After the coughing has stopped and the tests have come back negative, a fresh battle begins for some Covid-19 patients. Symptoms typically include headaches, lethargy, anxiety and insomnia, exhaustion and irritability. Some dream frequently about death. Others develop phobias linked to the places or activities that likely expose them to the virus.

Suhrita Basak, a 48-year-old businesswoman from Delhi, is still scared of basements, two months after she tested negative for Covid-19. "I don't like to go down there. I think that's where I contracted the virus, while sorting through my material," she says.

She finds it hard to take stairs below street level, even to a clinic. She sometimes sees flashes from her ambulance ri...