Also, according to the top health body of the US government, recovered people can have low levels of the virus in their bodies for up to three months after first diagnosis, but such people do not transmit the virus to others.
There has been no case of a recovered patient having been re-infected with the novel coronavirus till now, the Centres for Disease Control and Prevention (CDC) in the United States has said.
But recovered people can have low levels of the virus in their bodies for up to three months after they were first diagnosed, and this can be detected in the diagnostic tests. This is the reason why there have been instances of recovered people having tested positive again within the three-month period.
But such people do not transmit the virus to others, the CDC said in a new guidance released over the weekend.
“Reinfection with SARS-CoV2 (the virus responsible for the Covid-19 disease) has not yet been definitively confirmed in any recovered persons to date. If, and if so when, persons can be reinfected with the SARS-CoV2 remains unknown, and is a subject of investigation,” the CDC, which is part of the United States Department of Health, said.
The assertion can put to rest speculation about people getting re-infected with the virus.
The CDC, however, did not say that recovered patients develop immunity for three months, just that there has been no confirmed case of a re-infection during this time. It said retesting a person within the three month period was therefore “unnecessary”.
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Even if they test positive, it most probably would be because of left-over traces of virus (“persistent shedding”) rather than a case of re-infection.
The CDC also said that persons with mild to moderate symptoms can be released from isolation 10 days after they first tested positive, while those with severe symptoms need to be kept in isolation for a maximum of 20 days.
“Available data indicate that persons with mild to moderate Covid-19 remain infectious no longer than 10 days after symptom onset. Persons with more severe to critical illness or severe immunocompromise likely remain infectious no longer than 20 days after symptom onset,” it said.
“Recovered persons can continue to shed detectable SARS-CoV2 RNA in upper respiratory specimens for up to three months after illness onset, albeit at concentrations considerably lower than during illness, in ranges where replication-competent virus (those that can replicate and spread) has not been reliably recovered and infectiousness is unlikely. The etiology (cause of the disease) of this persistently detectable SARS-CoV2 RNA has yet to be determined,” it said.
“Studies have not found evidence that clinically recovered persons with persistence of viral RNA have transmitted SARS-CoV-2 to others,” it said.
The CDC said its new recommendations were based on more than 15 international and US-based published studies that looked at the length of infection, duration of viral shed, asymptomatic spread, and the risk of spread among various patient groups.
“Researchers have found that the amount of live virus in the nose and throat drops significantly soon after the Covid-19 symptoms develop. Additionally, the duration of infectiousness in most people with Covid-19 is no longer than 10 days after symptoms begin, and no longer than 20 days in people with severe illness…,” it said.
It said the latest findings strengthened the case for relying on “symptom-based, rather than test-based strategy for ending isolation” of infected patients, so that persons who are “by current evidence no longer infectious are not kept unnecessarily isolated and excluded from work or other responsibilities”.
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