Can you get coronavirus twice? Scientists don't have a definitive answer yet
There is currently neither a vaccine to prevent COVID-19 nor drugs to treat the deadly new coronavirus that has killed over 119,800 and infected more than 19,24,870 globally. However, over 458,000 have also recovered globally from the disease, according to the Johns Hopkins tracker. So what happens after people recover from the disease?
Are people still infectious after they recover?
They could be, but it is not clear yet how long someone retains the virus in their body. Patients may remain contagious long after their symptoms disappear.
In one study, researchers found that half of the patients they treated for mild COVID-19 infection still had coronavirus for up to eight days after symptoms disappeared. The most significant finding from the study — published online in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine — is that half of the patients kept shedding the virus even after their symptoms went away. More severe infections may have even longer shedding times, say experts. "COVID-19 patients can be infectious even after their symptomatic recovery, so treat the asymptomatic/recently recovered patients as carefully as symptomatic patients," said the research team.
In another study, researchers found that the virus can survive in a patient’s respiratory tract for 37 days, which implies that they could remain infectious for many weeks. Researchers found that the median duration of viral shedding was 20 days in survivors (ranging from 8 to 37 days), and the virus was detectable until death in the 54 non-survivors. While prolonged viral shedding suggests that patients may still be capable of spreading COVID-19, experts caution that the duration of viral shedding is influenced by disease severity, and note that all patients in the study were hospitalized, two-thirds of whom had a severe or critical illness.
Can you catch COVID-19 a second time?
According to experts, in general, once a person has recovered from a viral infection, the body will keep cells called lymphocytes in your system.
"These cells 'remember' viruses they’ve previously seen and can react quickly to fight them off again. If you are exposed to a virus you have already had, your antibodies will likely stop the virus before it starts causing symptoms. You become immune. This is the principle behind many vaccines," writes an expert. "Unfortunately, immunity isn’t perfect. For many viruses, like mumps, immunity can wane over time, leaving you susceptible to the virus in the future," says the article.
Since this is a new coronavirus, scientists still do not know whether people who recover from COVID-19 are immune to future infections of the virus.
According to the CDC, there are no data concerning the possibility of re-infection with SARS-CoV-2 after recovery from COVID-19. "Viral RNA shedding declines with a resolution of symptoms and may continue for days to weeks. However, the detection of RNA during convalescence does not necessarily indicate the presence of viable infectious virus. Clinical recovery has been correlated with the detection of IgM and IgG antibodies which signal the development of immunity," says the CDC.
During a briefing on April 13, Dr Mike Ryan, executive director, World Health Organization (WHO) Health Emergencies Programme, said, “With regards to recovery and then reinfection, I believe we do not have the answers to that. That is an unknown.”
South Korea recently reported that over 90 patients who were thought to have been cleared of the new coronavirus had tested positive again. The World Health Organization (WHO) now says that it is investigating reports that coronavirus patients — who initially tested negative but later tested positive for the virus a few days later.
“We are aware of these reports of individuals who have tested negative for COVID-19 using PCR (polymerase chain reaction) testing and then after some days testing positive again. We are closely liaising with our clinical experts and working hard to get more information on those individual cases. It is important to make sure that when samples are collected for testing on suspected patients, procedures are followed properly,” the WHO told Reuters.
How long does immunity last?
The answer to this is not known yet. According to CDC experts, the immune response, including duration of immunity, to SARS-CoV-2 infection is not yet understood. Patients with MERS-CoV are unlikely to be re-infected shortly after they recover, but it is not yet known whether similar immune protection will be observed for patients with COVID-19, say experts.
Should you step out or go back to work?
Since determining when a patient has recovered is still fraught with uncertainties, it might be best to observe social distancing for some time, say experts. The CDC says that the decision to discontinue home isolation should be made in the context of local circumstances. "Options now include both a time-since-illness-onset and time-since-recovery (non-test-based) strategy, and a test-based strategy," says the CDC.
The CDC advises persons with COVID-19, who have symptoms and were directed to care for themselves at home, may discontinue isolation after taking into consideration some important factors. This includes not having a fever for at least 72 hours, or three full days of no fever without the use of medicine that reduces fevers. Other symptoms should have improved, for example, cough or shortness of breath. Another consideration is at least seven days have passed since the symptoms first appeared.
If a person is tested to determine if they are still contagious, they can leave home after three things have happened. "You no longer have a fever (without the use medicine that reduces fevers), other symptoms have improved (for example, when your cough or shortness of breath has improved), and you received two negative tests in a row, 24 hours apart," says the CDC.