Some Covid-19 patients might be capable of transmitting the virus even after all symptoms of the disease disappear, a new study has found, and recommended that the quarantine period for seemingly cured people be extended to avoid any possibility of infection.
The findings hold significance for India, which is not only struggling to tamp down on quarantine breakers but also has one of the lowest rates of testing in the world. Many experts say the low testing rate has left the government with inadequate data on the scale of the infection spread.
The study, published in the American Journal of Respiratory and Critical Care Medicine on Friday by researchers from China and the US, examined patients treated at the Chinese PLA General Hospital in Beijing between January 28 and February 9. The patients studied had a median age of 35.5 and were mild Covid-19 cases.
For the study, the researchers collected throat swab samples from the patients discharged after their recovery and confirmation of negative viral status by two consecutive polymerase chain reaction (PCR) tests.
“The most significant finding from our study is that half of the patients kept shedding the virus even after resolution of their symptoms,” said Dr Lokesh Sharma, department of medicine, Yale School of Medicine. “More severe infections may have even longer shedding times.”
The primary symptoms in these patients included fever, cough, pain in the pharynx and difficult or laboured breathing.
For these patients, the time from infection to onset of symptoms (incubation period) was five days among all but one patient. The average duration of symptoms was eight days, while the length of time patients remained contagious after the end of their symptoms ranged from one to eight days.
“If you had mild respiratory symptoms from Covid-19 and were staying at home so as not to infect people, extend your quarantine for another two weeks after recovery to ensure that you don’t infect other people,” said Lixin Xie, professor, College of Pulmonary and Critical Care Medicine, Chinese PLA General Hospital, Beijing.
The paper noted it was unclear whether similar results would hold for more vulnerable patients such as the elderly, those with suppressed immune systems and patients on immunosuppressive therapies, and called for more research.
This finding about the shedding window – the time period in which a person can shed the virus and therefore spread the infection – holds special significance for countries such as India, which are still in the initial phase of the outbreak but are hampered by poor healthcare infrastructure and monitoring.
“The main importance of these finding is that patients needs be monitored for viral negative status [two consecutive times, separated by at least 24 hours] after resolution of the symptoms. This is the standard protocol followed by most of the countries,” said Sharma.
But he admitted that such protocol could be tricky in South Asian countries including India, where testing facilities have been limited. “In these cases, patients should remain quarantined at home or at hospital [which can be difficult] even after the resolution of symptoms for at least two weeks to ensure that they do not spread the virus,” he added.
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