Brazil is experiencing an increase in cases and people with symptoms of covid-19, after the relaxation of some health measures, such as the mandatory use of masks. With the discharge of the disease, an important question that has been studied and discussed is how long the virus can stay in the body.
According to infectologist Alexandre Vargas Schwarzbold, the length of stay of Sars-CoV 2 in the respiratory tract for the omicron and its subvariants does not change much in relation to the previous variants.
“On average, it lasts nine days, but depending on the viral load, it can last less time in a person’s body, from five to seven days, or more, reaching 14 days. In patients with some immunosuppression, the duration and viral excretion it can last even longer, reaching two weeks or even a month”, says the doctor who is also a professor of infectology at the UFSM (Federal University of Santa Maria) and a consulting member of the SBI (Brazilian Society of Infectious Diseases).
Broadly speaking, peak transmission before the micron was between two days before symptoms emerged, and three days later, with viral load gradually decreasing over seven to 10 days. For the Ômicron, the consensus is between two days before and two days after the onset of symptoms, according to Ana Luíza Gibertoni Cruz, an infectious disease specialist at the UK Health Security Agency and a researcher at the Department of Population Health at the University of Oxford, in England.
“However, it is important to convey the uncertainty that exists in these estimates, mainly because the data come from a heterogeneous population for vaccine and disease status, and not from a homogeneously non-immune population”, comments Cruz.
Currently, the recommended isolation for patients with covid-19 varies from five to 10 days in Brazil, depending on the symptoms and tests carried out by the patient.
Immunity, viral load and vaccination influence
The length of time the virus remains in the body can vary depending on factors such as the person’s previous health status, the amount of virus they have been infected with, and vaccination status (vaccinated people have a shorter duration of the virus in the body than unvaccinated people). , possibly because they have a lower viral load).
“One of the main factors that define the length of time the virus stays in the body is the person’s immunity. And the greater the age, the lower the competence of the immune system”, says Rosana. Richtmanninfectious disease specialist at the Emilio Ribas Institute of Infectious Diseases and director of the Brazilian Society of Infectious Diseases.
According to her, they also involve factors such as previous immunity acquired by vaccination or natural disease, and factors related to genetics and immunosuppression conditions. “Someone undergoing cancer treatment, for example, may have a lower immune response and a longer period of time for the virus to remain in the body,” she says.
What is the best test to know if an infected person is transmitting the virus?
The elimination of the virus from a person’s body occurs almost simultaneously with the improvement of respiratory and systemic symptoms. But, according to the experts heard by the report, an objective way to know if the infected individual no longer transmits the virus is through the rapid antigen test, as it can detect viral replication (virus still in activity) and indicate if the amount virus present is sufficient to allow person-to-person transmission.
The RT-PCR test is good and recommended for diagnostic purposes, but not to know if the infected person can still transmit, because it is extremely sensitive and can detect any structure of the virus, whether or not it is viable, says Richtmann, which gives a purely didactic example.
“Imagine that the virus is an ant in the throat. If the person does the PCR test and the ant is alive, the result will be positive. PCR test will still be positive”, he compares.
That is, a person who has had covid-19 can be PCR positive for weeks, but this does not mean that he is still sick or that he can transmit the disease. A positive test can be misinterpreted and put an individual into prolonged isolation unnecessarily.
Cruz, a researcher from Oxford, explains that the virus can continue in the body without transmission being possible. “People who still have active virus but replicating at a low rate do not tend to transmit the virus, probably because there is little active particle being mobilized through the droplets and aerosols formed by respiratory secretions,” she says.