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Isolation should be done for at least ten days after the onset of symptoms.
Many viruses continue to spread even long after the infected person’s symptoms have disappeared; a cough or fever are not the only indicators that a person can infect others with a virus.
This is the case with the new coronavirus, Sars-Cov-2, which can remain contagious even after symptoms disappear, research shows. But for how long?
What about people who never had symptoms or where the symptoms were so mild that they went unnoticed?
Incubation
Since Sars-Cov-2 was detected in China last December, several scientific teams have been investigating the incubation period of the new coronavirus, that is, how long the virus remains in the body.
One such study, conducted by researchers at Johns Hopkins University in the United States and published in the Annals of Internal Medicine in May, estimated that the average incubation period for the new coronavirus is 5.1 days.
But this is the average period; it can be longer or shorter, depending on the person’s body. Most (97.5%) of those infected who develop symptoms do so before reaching 11.5 days from the time a person was exposed to the virus through the nose or mouth, according to the study.
“The ability to infect other people, to transmit this virus to other people, lasts from 7 to 10 days after the onset of symptoms”, explains the infectologist Vicente Soriano, professor at the International University of La Rioja, in Spain. and a former advisor to the World Health Organization (WHO).
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Testing and screening are important to detect asymptomatic people
He adds that, from that moment, when the symptoms have passed or have disappeared, the possibility of infecting other people also decreases.
However, the expert notes that the PCR tests used to detect the virus can continue to test positive for several days or weeks after infection with the virus. That is, the virus can remain in the person’s system.
“The PCR, which detects fragments of the virus genome, can remain positive for one, two or even three weeks after the cure of the disease,” says Vicente Soriano.
“But that positive PCR does not reflect contagion. What the PCR detects are virus fragments, or ‘garbage strings’, which are fragments of the virus genome that are found in the respiratory tract and that we expel for several weeks after they are has cured the disease.. “
In fact, the sensitivity of diagnostic tests has been a familiar topic since they began to be applied and is an example of how research on Covid-19 is still in its infancy.
But, as Soriano emphasizes, “the contagion of the coronavirus is basically 7 to 10 days, one or two days before the onset of symptoms and while symptoms occur,” he adds.
That is, a person with coronavirus is no longer contagious about 10 days after the onset of symptoms. But you have to be careful before you leave isolation: make sure you have no further symptoms and that you have not had a fever for at least 24 hours without using the medications that control it.
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Masks reduce the risk of someone infected and asymptomatic transmitting the disease
Asymptomatic cases
But what happens when a person is infected with the coronavirus and has no symptoms? How do you know that you will not infect other people?
Although several studies have been published on the percentage of infected people who are asymptomatic, the WHO says that it is not possible to increase an exact number.
The official position of the organization indicates that a recent systematic review of the scientific literature shows that asymptomatic cases could vary between 6% and 41% of contamination cases, that is, there is still great uncertainty about what proportion of cases asymptomatic among the contaminated.
The WHO explains that “most of the studies included in these reviews had significant limitations in terms of reporting symptoms, or did not adequately define which symptoms were being investigated.”
In addition, explains the entity, many people who believe they are asymptomatic actually had some symptoms, but very mild, which ended up going unnoticed.
There is also the case of people who have been diagnosed with covid-19, they still do not have symptoms, but they will develop them in the future, they are presymptomatic people.
In any case, the researchers found that people without symptoms and with covid carry a large number of viruses in the body – the same number of viruses as patients with symptoms. And both remain with this viral load at the same time.
Therefore, experts emphasize the importance of wearing masks and observing social distance. These two measures can help reduce the risk of someone with COVID-19 and no symptoms infecting others.
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There is no certainty about the percentage of infected people who are asymptomatic.
“Basically, people without symptoms can transmit viruses to other people for a week, just like those with symptoms, but unless the person has an antigen test (to detect that they have the disease) or a PCR, that person goes unnoticed. ” Soriano says.
“Hence the interest in screening to identify people who may have been in a contagious area and undergo antigen or PCR testing 48 hours after the event.”
That way, the expert says, asymptomatic and presymptomatic patients can be identified and kept isolated for 10 days to prevent other infections.
Serious patients
However, these recommendations do not apply to people who have had more severe symptoms of Covid-19 and have not been hospitalized.
As the U.S. Centers for Disease Control and Prevention (CDC) notes, in many cases, when a person was seriously ill and has not been hospitalized, they will have to stay home for 20 days after the initial onset of the symptoms. symptoms.
Also, people with weakened or immune systems who have had the disease will need to stay home longer and see their doctor to see when they can stop isolating themselves.
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