Patients with mild symptoms of covid-19 may be able to transmit the new coronavirus for longer than previously believed. The hypothesis was raised in a study by the Institute of Tropical Medicine of the University of São Paulo (IMT-USP), recently published in medRxiv.
The research conducted by IMT-USP professor Maria Cassia Mendes-Correa, under review by the scientific community, was based on the cases of two patients in whom Sars-CoV-2 was active in the organism for more than 30 days, exceeding 14 isolation days indicated in Brazil.
One of the women, seen for the first time in April 2020, lived with dry cough, weakness, headaches, in the body and joints for more than 20 days. The presence of the virus was confirmed by means of an RT-PCR exam carried out 22 days after the onset of the condition.
Loss of smell and taste, vomiting and nausea followed, requiring a new test 37 days after the start, which again was positive. Most symptoms did not disappear until mid-May, according to the article.
Insulation term review
The second patient presented fever, cough, runny nose, headache, in the joints and body, nausea and weakness in May. She tested positive five days after the onset of symptoms, which persisted and led to a new test, 24 days later, still indicating the presence of the coronavirus. In total, there were 35 symptomatic days.
As these are atypical cases, the patients’ nasopharyngeal secretion samples underwent a thorough analysis. “The material was inoculated into a culture of epithelial cells and, after several tests, we confirmed that the virus present there was still viable, that is, it was able to replicate and infect other people”, said the leader of the study.
The research group followed up with 50 other people in a similar situation – mild and prolonged symptoms. In 18% of cases, the RT-PCR test indicated Sars-CoV-2 active for up to 50 days. “Among these, 6% remained transmitters (with the virus still multiplying) for 14 days”, commented the teacher.
According to Mendes-Correa, the result of the study shows that the 10 days of isolation recommended by the United States Disease Control Center (CDC) for mild conditions may not be ideal for preventing further contamination.
Broadcast over several months
The researcher also reported the existence of immunosuppressed patients who can remain infected for a longer time. One of the volunteers, who has undergone a bone marrow transplant, has been in isolation for six months.
Monitoring cases like this is essential, as they offer the ideal conditions for even more aggressive variants of the coronavirus to appear, according to the author.