Picture used for representational purpose only NEW DELHI: The novel coronavirus variant that is causing the current wave of Covid-19 is not just highly infectious but also stealthy. City hospitals say there are getting cases where a patient has typical symptoms of the disease but tests negative for the viral infection, sometimes twice or thrice even through RT-PCR, considered the gold standard for Covid testing. “We have received many such patients in the past few days. They had fever, cough, shortness of breath and the CT scan of the lungs showed lighter-coloured or gray patches. It is referred to as patchy ground glass opacity in medical terms. The condition is one of the defining characteristics of Covid-19,” Dr Aashish Chaudhry, managing director of Aakash Healthcare, said.