Are cases of re-positive SARS-CoV-2 infectious?

About 5-10% of recovered patients test positive again.

Although there are currently no official statistics on the rate of recovered patients "retesting positive" for the SARS-CoV-2 virus, according to reports from many quarantine areas in Wuhan city, Hubei province, this number fluctuates between 5 and 10%.

Nghe An Provincial Center for Disease Control tests patient samples. Photo courtesy of Thanh Cuong

Frontline facilities in the fight against Covid-19 have confirmed that there have been no cases of recovered patients who later tested positive again and were able to infect others.

Yang Zhangqiu, a virologist at Wuhan University, said factors such as testing methods or patient samples could lead to "false positive" or "false negative" results.

A recovered patient who tests positive again is someone who tested positive and then negative after treatment or even without treatment but then tested positive again.

However, calling all these cases "reinfection" is probably inappropriate, according to Mr. Yang, and people should wait for a longer period of time, such as several months, to see if the results continue to be positive.

SARS-CoV-2 can survive in the gut for a long time

A Chinese immunologist told reporters that the new coronavirus can still survive in the human body, especially the intestines, for a long time.

For example, scientists used electron microscopy to observe SARS-CoV-2 in the gut from the stool of a group of people from southern India. It turned out that some people were able to continuously excrete particles containing SARS-CoV-2.

However, these virus-containing molecules have virtually no nucleic acid, meaning they are just empty protein shells with no nucleic acid carrying genetic material inside.

In theory, if healthy people receive these empty virus shell proteins, they could gain immunity against the real virus, the expert said, adding that this could create a kind of "natural vaccine" that would help people in an area achieve herd immunity against the virus.

The "war" between virus and immune system

If the reason does not come from testing procedures or related methods, we need to think about the above "re-positive" cases possibly from the perspective of the patient's immune system and the incubation period of the virus, especially when the patient has symptoms again, such as fever, experts said.

Because there are currently no drugs to treat Covid-19, a patient’s recovery depends entirely on their immune system “clearing” the virus. However, so far, patients have been declared recovered and discharged without testing for immune markers such as antibody valency or immune cells.

When someone has Covid-19, their immune system can be severely compromised. When some patients are discharged from the hospital, the novel coronavirus is only temporarily “overwhelmed” by the immune system, so tests cannot detect it in some tissues or cells.

In these cases, if the patient has not fully recovered or has not had adequate rest, the immune system may weaken again, especially in the elderly, those in poor health or those who have used glucocorticoids. They may be at risk of re-infection with the virus that has been latent in the body.

Notably, according to experts, some of these cases may actually be infected and have the ability to transmit the virus to others.

However, experts also assert that people should not panic about these cases but should pay more attention to them. We should set up mechanisms, such as setting up centralized recovery care centers to ensure that the immune systems of these patients are also fully recovered.

Once patients have fully recovered and are discharged from the hospital, they should undergo all additional rehabilitation phases in designated recovery facilities. This not only allows them to better restore their immune system but also controls and limits the risk of infection.

During this recovery phase, patients can use immunomodulators and nutritional supplements. When all immune indicators have returned to normal, they can safely return home.

Based on research from a team of scientists led by scholar Tong Xiaolin of the Chinese Academy of Sciences, traditional Chinese medicine can reduce the rate of re-positive by about 2.5%./.