Coronavirus: When a Covid-19 Infectee Ceases to be Contagious, With or Without Symptoms
RIO DE JANEIRO, BRAZIL – Many viruses continue to spread even long after the infected person’s symptoms have subsided – 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 continue to be contagious even after the symptoms have subsided, according to research. But for how long?
And in the case of people who never had symptoms or in whom the symptoms were so mild that went unnoticed?
Incubation
Since Sars-Cov-2 was detected in China last December, several scientific teams have been investigating the incubation period of the novel coronavirus – that is, how long the virus will remain in the body.
One of these studies, conducted by researchers from Johns Hopkins University in the United States, and published in the “Annals of Internal Medicine” scientific journal in May, estimated that the average incubation period for the novel coronavirus is 5.1 days.
However, this is the average period – it can be longer or shorter, depending on the person’s organism. The majority (97.5 percent) of infectees who develop symptoms do so before reaching 11.5 days from the time of exposure to the virus through the nose or mouth, according to the study.
“The ability to infect other people, to pass this virus to other people, lasts from seven to ten days from the appearance of symptoms,” explains infectologist Vicente Soriano, professor at the International University of La Rioja, Spain, and former adviser to the World Health Organization (WHO).
He adds that from that moment on, when the symptoms have either subsided or disappeared, the possibility of infecting other people also decreases.
However, the specialist points out that the PCR tests used to detect the virus may continue to give a positive result for several days or weeks after infection with the virus. In other words, the virus may remain in the individual’s system.
“The PCR test, which detects fragments of the virus genome, can continue to be positive one, two or even three weeks after being cured of the disease”, Vicente Soriano points out.
“But that positive PCR does not reflect contagiousness. The PCR detects virus fragments, or ‘debris sequences’, which are fragments of the virus genome in the respiratory tract and which we expel for several weeks after we have been cured”.
In fact, the sensitivity of diagnostic tests is a known challenge since they began to be used, and is an illustration of how research on Covid-19 is still in its early stages.
But, as Soriano stresses, “the contagiousness of the coronavirus is basically from seven to ten days, one or two days before the onset of symptoms and while symptoms occur,” he adds.
That is, a person infected with the coronavirus ceases to be contagious about ten days after the onset of symptoms. But care must be taken before leaving confinement: making sure there are no more symptoms and that no fever has been present for at least 24 hours without the use of drugs to control it.
Asymptomatic cases
But what happens when a person is infected with the coronavirus and has no symptoms? How to know that he/she will not infect other people?
Although several studies have been published on the percentage of infected people who are asymptomatic, the WHO states that it is not possible to pinpoint an exact number.
The organization’s official position states that a recent systematic review of the scientific literature shows that asymptomatic cases could vary between six and 41 percent of infections, i.e., there is still considerable uncertainty regarding the proportion of asymptomatic cases among those infected.
The WHO explains that “most studies included in these reviews had significant limitations as to the reporting of symptoms, or did not accurately define which symptoms were being investigated”.
Furthermore, the organization explains that many people who believe they are asymptomatic actually had some symptoms, albeit very mild, which ultimately went unnoticed.
There is also the case of people who were diagnosed with Covid-19, do not have any symptoms yet, but will develop them in the future – these are the pre-symptomatic individuals.
In any case, researchers have found that people with no symptoms and with Covid carry a high amount of virus in the body – the same amount as symptomatic patients. And they both retain this viral load for the same amount of time.
Therefore, experts stress the importance of wearing masks and observing social distancing. These two measures can help reduce the risk that an individual with Covid-19 and symptom-free will infect others.
“Basically, people with no symptoms can pass the virus on to other people for a week, just like symptomatic individuals, but unless a person is tested for the antigen (to detect that they are infected) or a PCR test, that individual will go unnoticed,” Soriano says.
“Hence the interest in conducting screening to detect people who may have been in the area of contagion and perform the antigen or PCR test from 48 hours after the event”.
This way, asymptomatic and pre-symptomatic individuals can be found and isolated for ten days to prevent further infections.
Critical patients
However, these recommendations are not applicable to individuals who have had more severe covid-19 symptoms and have not been hospitalized.
As pointed out by the Centers for Disease Control and Prevention (CDC) of the United States, in many cases, when an individual was critically ill and has not been hospitalized, he or she will be required to remain at home until 20 days after the initial onset of symptoms.
Furthermore, people with immune system disorders or weakened immune system who have had the disease will need to stay home longer and see their doctor to determine when they can end their isolation.
Source: BBC
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This article was produced by The Rio Times’ automated newsroom system. How we use AI · Report an error · Editorial responsibility: Matthias Camenzind, Editor-in-Chief