A father and his daughter in the city of Xuzhou, in the Chinese province of Jiangsu, have become the last known cases so far of a group that continues to increase: that of patients infected by the new coronavirus who recover to , after a few days or weeks, test positive again. A phenomenon that worries doctors, because it can make Covid-19, the disease caused by the virus, more difficult to eradicate.
According to Chinese state media, the father, the first confirmed case in that city, had been discharged from the hospital two weeks ago, but in a new test he has returned positive as a carrier of the virus. His young daughter, who had also been declared cured, has yielded the same result. Both have been re-entered.
Two days earlier, the local government of Osaka Prefecture in Japan had confirmed another similar case: that of a tourist guide in his forties who had become ill in January and had been discharged in early February. He returned to show symptoms, such as dry cough and chest pain, and on February 26 he tested positive. This patient had not returned to work, had remained at home, had not maintained close contact with anyone and had always worn a mask when leaving.
Throughout China, other cases of new positives have been detected among people declared previously cured. A study conducted among patients who left the hospital in the province of Canton, in the southeast, found that 14% of the cases were positive again, according to Caixin magazine on Tuesday.
Concern about possible reinfections has led the authorities of Wuhan, the city where the epidemic originated, to order that the patients of Covid-19 who are discharged from the hospital have to spend a quarantine of fourteen days in a specially enabled center before of being able to return to normal life.
Experts see several possible explanations for a discharged affected person to relapse again. One possibility is that a small amount of virus has remained in the body, insufficient to test positive, but enough to reproduce and return positive if the body has not developed antibodies in adequate amounts to fight it. It is also possible that this lack of antibodies allows a second infection from external sources.
"It is a pattern that has occurred in outbreaks of other diseases," recalls Professor of Statistical Epidemiology Christl Donnelly, Imperial College London and the University of Oxford. In the case of the Ebola epidemic in West Africa between 2013 and 2016 - he gives as an example - there were cases in which, when the tests were repeated before the final discharge, relapses were recorded. "It is also possible that it occurs as in the case of shingles, a consequence of a previous infection with the chickenpox virus, in which the virus is dormant somewhere in the body," for years.
The question in these cases of positive after cure, Donnelly points out, is that “we do not know if these affected can infect other people later. If it happened, it would cause those seemingly recovered cases to be a potential source of infection, which would be a concern. We have to wait and see what happens with these people, and carefully follow the clinical data that comes out. ”
The National Health Commission in China has declared Friday that the first examinations of these patients have found that they are not infectious. Another possibility that is handled is that, at least in some cases, the tests to discharge have not been done correctly. Or that they have been done correctly and have thrown false negatives: Dr. Li Wenliang, who tried to raise the alarm at the beginning of the crisis that died from Covid-19 on February 6, gave negative several times before his confirmation was confirmed. infection.
Speaking to the People's Daily , the newspaper of the Communist Party of China, the deputy director of the center of infectious diseases at the Hospital of Western China explained that doctors initially took samples of the nose and throat to determine if a patient was a carrier of the coronavirus. Other more recent tests find traces of the pathogen in the lungs.
In Japan, the criteria for the discharge of a patient from Covid-19 provide for the patient to be negative in a test carried out 48 hours after he has stopped presenting serious symptoms, and that the result is the same in a second exam twelve hours later.
In China, patients must test negative, have no symptoms and their lungs must not have abnormalities on a CT scan.
In a press conference this week, the deputy director of the Center for Disease Control and Prevention in Canton, Song Tie, said that none of the patients infected for the second time seems to have infected the people around them. "From what we understand, after someone has been infected by this type of virus, it will produce antibodies, and after these antibodies have been produced, it will not be contagious."
So far, more than 78,000 infected with the coronavirus in China since the crisis began two months ago, 36,117 patients have already been discharged, almost half.