On 15 August, a 33-year-old man landed in Hong Kong after flying home from Spain. On arrival, he was screened for coronavirus. Despite feeling well he tested positive. It was the second time he had picked up Covid-19 in less than five months. The case immediately caught scientists’ attention. The man was the first in the world to have a confirmed coronavirus reinfection and there were positives to take from the report. First and foremost, he was asymptomatic. Although reinfected with Sars-Cov-2, his immune system swung into action fast and contained the virus without him knowing. Many researchers took heart from the case, but since the patient came to light a flurry of reinfections around the world have raised fresh concerns. Within days of the Hong Kong case being made public, doctors in the US reported that a 25-year-old man from Reno, Nevada, had been hospitalised with a Covid-19 reinfection after shrugging off an earlier brush with the disease. More cases soon followed. While most infections were no worse the second time around, a good number cropped up – in the US, the Netherlands, Ecuador and India – where the reinfection was more severe. “It’s really hard to find a pattern right now,” said Akiko Iwasaki, a professor of immunobiology at Yale University who has been following cases of reinfection closely. “Essentially every case is different.” So far, only two dozen or so reinfections have been confirmed worldwide in a pandemic that has infected more than 30 million people. For now at least, reinfection seems uncommon. But scientists point out that confirming reinfection is no easy task and many cases are missed. To confirm a reinfection, scientists must examine the genetic code of the virus from each round of illness and prove they are distinct. That means having access to both sets of swabs and the wherewithal to do whole genome sequencing. Even in hospitals where the capacity exists, such tests are rarely done. Reinfected patients simply go unnoticed or unreported. “There is probably a lot more than we are seeing,” said Iwasaki. The immune system’s battle against coronavirus is unleashed in several waves. The first line of defence, the innate immune system, is imprecise but fast. Invading pathogens prompt cells to churn out signalling proteins called cytokines which call in an army of white blood cells that engulf and disrupt the virus. Next to gear up is the adaptive immune system, a more specialised attacking force. This unleashes T-cells, which destroy infected cells, and prompts B-cells to make antibodies that stick to viruses and stop them spreading further. If and when the infection is beaten, the T- and B-cells stand down, but some should be stored in the body for years, an immune memory that can be recommissioned should the virus try again. Given the complexity of the immune response, it is no surprise that scientists are struggling to unravel why reinfections occur. Blood tests on patients reveal that virus-disabling
Related Posts
