Covid-19: Stealthy virus beating RT-PCR tests, find docs

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.

He added that some of the patients underwent bronchoalveolar lavage (BAL), a diagnostic method in which a flexible scope is passed through the mouth or nose into the lungs with a measured amount of fluid introduced and then collected for examination, which confirmed the diagnosis.

“All such persons who tested negative through conventional Covid-19 testing methods but had disease symptoms came positive in the lavage test,” Dr Chaudhry said.

What could be causing this? Dr Pratibha Kale, associate professor of clinical microbiology at Institute of Liver and Biliary Sciences, said, “It is possible that in these patients the virus didn’t colonise the nasal or throat cavity because of which swab samples taken from these areas didn’t yield a positive result.” The virus, she added, attached itself to the ACE receptors — a protein found on the surface of many cell types — in the lungs and “that’s why when the fluid samples from the organ were analysed, it confirmed Covid-19 diagnosis”.

Dr Vivek Nangia, the chief of pulmonology division at Max Healthcare, said nearly 15-20% of the Covid-19 patients suffered from this problem. “They are highly symptomatic of the disease, but test negative. This is a serious problem because such patients can continue to spread the infection if they are admitted in non-Covid areas. Also, it can delay the treatment,” he added.

The pulmonologist said the symptoms in Covid patients also varied significantly in the current wave compared to previous outbreaks caused by SARS-CoV-2. “A significant mutation in the virus cannot be ruled out. It is the most plausible explanation for the changes being witnessed,” he said.

Dr Arup Basu, senior consultant in the chest medicine department of Sir Ganga Ram Hospital, said nose running, cold and conjunctivitis like symptoms were also being seen in Covid-19 patients this time, which were not present earlier. “Many patients do not have cough or breathlessness and the result of the CT scan of their lungs is also normal. However, they have persistently high fever for eight to nine days that necessitates hospitalisation,” he said.