Days before Nikita Goel had planned to get married, she and five family members tested positive for the coronavirus, including her parents and 86-year-old grandfather. “I felt like a roof had fallen,” she said. Her father and grandfather were soon fighting for every breath, and Ms. Goel, suffering fever and coughing fits, was the one sent to find help from an overwhelmed healthcare system collapsing around her. “I suddenly felt I was left alone in the world, alone to save my family,” said Ms. Goel, 28 years old. The wave of Covid-19 sweeping India has hit hard and suddenly, swallowing entire families and neighborhoods and, in many cases, leaving the sick to care for the sicker. Those still healthy risk infection in crowded pharmacies, clinics and hospitals trying to find medicine and medical help for loved ones.