Scientists this week confirmed a new coronavirus reinfection in a 33-year-old man in Hong Kong, who had Covid-19 in March and was found to be infected with a different variant of the virus after 142 days during a visit to Europe. They used genetic sequencing to confirm that the second infection was caused by a genetically different virus from the one that caused the first infection in March.
The otherwise healthy man had developed a cough and sputum, and was depressed with a sore throat, fever, and headache for three days when he first tested positive for Covid-19, but was asymptomatic when he returned to infect in August, according to the newspaper. study published in the journal Clinical Infectious Diseases.
The study reignited the debate over whether true reinfection can occur. Studies show that after infection with Sars-CoV2, the virus that causes Covid-19, the infected person produces neutralizing antibodies rapidly, but antibody titers (count) begin to decline in about one to two months after infection. sharp.
Read the Unlock 4.0 guidelines here
But prolonged low-grade viral shedding detectable by reverse transcription polymerase chain reaction tests has led to people testing positive weeks after recovery. In the past, recovered people tested positive again after a few weeks in South Korea, China, and some European countries, raising fears of reinfection, but scientists clarified that repeated positive tests detected dead viruses from past infections that did not they affected the person. others sick or infected.
Genetic confirmation in Hong Kong showed that a second infection can occur, but there are no reports of people developing symptoms or getting sick a second time.
“Now we are starting to see cases of reinfection, but so far we have not had a true reinfection where a person had symptoms the first time and had symptoms the second time. We only have cases of symptomatic the first time and asymptomatic the second time. A true reinfection has not yet occurred with a patient presenting with two symptoms, ”said Dr. Anurag Agrawal, director of the Council for Scientific and Industrial Research at the Institute of Genomics and Integrative Biology.
The immune system uses specificity, diversity, and memory to fight infection. Immunological memory involving T and B cells in the immune system leads to an adaptive antibody response that is faster, higher affinity, and results in the secretion of non-IgM IgG isotypes that provide longer lasting protection against reinfection.
“So even when neutralizing antibodies bind to the virus to immobilize it and the T cells fight it, the memory B and T cells in the immune system store virus recognition patterns for future reference. Neutralizing antibody levels can drop within three months, but memory B cells instantly recognize a new infection leading to the rapid deployment of the specific immune response pre-programmed to attack Sars-CoV2. So while it may not prevent reinfection, it will prevent damage to the body, ”said Dr. K Srinath Reddy, President of the Public Health Foundation of India.
The amount of live virus in the nose and throat decreases significantly shortly after Covid-19 symptoms develop, and the duration of infectivity in most people does not last more than 10 days after symptoms begin , and 20 days on average in people with serious illnesses or those who are severely immunosuppressed, according to the US Centers for Disease Control and Prevention.
A person who has recovered from Covid-19 can have low levels of the virus in their body for up to three months after diagnosis. “This means that if the person who has recovered is retested within three months of the initial infection, they can continue to have a positive result, even if they are not spreading Covid-19,” said the latest advisory from the CDC.
The only protection is the use of masks, social distancing and hand hygiene. “A lot of people are not using the social vaccine and are not taking precautions, such as maintaining social distancing and wearing masks. People take off their masks when talking, eating or having a conversation, which is the worst thing that can happen in terms of potential exposure to infected droplets, ”said Dr Shiv K Sarin, Director of the Indian Institute of Liver and Biliary Sciences . New Delhi, which established the country’s first convalescent plasma bank for treatment.
“You don’t need to remove your masks while speaking. Doctors, nurses and healthcare workers routinely communicate through masks and personal protective equipment (PPE), even during critical surgeries where lack of communication is not an option, ”said Dr. Reddy.
Since the disease is just over eight months old, it is not yet known how strong and long-lasting protective antibodies provide, but tests to detect them help track the scale of the pandemic and understand the spread of the infection. “The next survey in Delhi will tell us the silent exposure in the population. The latest serosurveillance found that about 30% of people have antibodies against Sars-CoV2 in Delhi, although we do not know how protective these antibodies are as they are not neutralizing, they offer longer protection, “he said.
“With the opening (after the closing), the cases will continue to increase. In the next survey I have the feeling that we can be 38% more or less positive in Delhi. The only way to protect people is to wear a mask and wear it properly covering our nose and mouth, ”he said.
.
