Are reports of coronavirus ‘reinfection’ a cause for concern?

‘The answer is that we do not know yet, [but] the general consensus amongst experts is that recovery from infection is likely to result in subsequent protection.’
 
When it comes to the question of immunity and COVID-19, that is the response of Professor Ian Henderson, Director of the Institute for Molecular Bioscience at the University of Queensland.
 
Research from China last month showed that between 3–14% of coronavirus patients tested positive for a second time after being released from quarantine. More recently in South Korea, 111 people tested positive for a second time, according to the Korea Centers for Disease Control and Prevention (KCDC).
 
While further epidemiological investigations are currently under way, KCDC Director Jeong Eun-kyeong told a briefing they believed it was not a case of ‘reinfection’ but rather that the virus had been ‘reactivated’ in the patients.
 
Australia’s Deputy Chief Medical Officer Professor Paul Kelly said while the numbers were relatively low, and not the normal trend, the prospect of possible reinfection was certainly ‘concerning’ and would need to be taken into account in the search for a vaccine.
 
‘We’ve only been in this fight against the virus for several months now, rather than years, and so it’s difficult to know what happens in the long term,’ he said during a press conference.  
 
‘Clearly if immunity does not last for a long time, then that has implications for the vaccine. And clearly if there is, for example, slight changes in the virus which leads us to be able to be reinfected, that also has vaccine implications and so we’ll have to take that into account.’
 
In South Korea, patients with COVID-19 must test negative twice within 24 hours before being released from isolation, while Australian guidelines currently require patients to test negative on two tests 24 hours apart. 
 
It is important to note that the relatively small numbers of cases in South Korea were tested within seven to 14 days after apparent recovery, according to the Australian Department of Health (DoH).
 
‘It is likely that positive tests soon after recovery represent persisting excretion of viral RNA, and it should be noted that PCR [polymerase chain reaction] tests cannot distinguish between “live” virus and non-infective RNA,’ the DoH states on its website.
 
That is the same point raised by Oh Myoung-don, a professor of internal medicine and member of the World Health Organization’s (WHO) Strategic and Technical Advisory Group for Infectious Hazards. Contrary to claims of possible reactivation of the virus, Professor Oh suggests the tests conducted in South Korea likely picked up lingering viral genetic material.
 
‘Even after the virus is dead, the nucleic acid [RNA] fragments still remain in the cells,’ he said.
 
Associate Professor Ian Mackay, a virologist at the University of Queensland Child Health Research Centre, told newsGP that until some scientific method is applied to these cases, they are merely ‘anecdotes about reinfection [with] no solid analyses to guide us’.
 
‘We can hypothesise that this is simply related to a single disease episode in which two tests returned virus-negative results, mainly because viral load was sputtering out in clinically well patients,’ he said.
 
‘The viral load may be dipping below and back above the limit of detection of even sensitive PCR-based tests as recovery concludes.’
 
This may also be something that occurs with influenza and other respiratory viruses, Associate Professor Mackay explained.
 
‘We may simply have missed it in the past because we haven’t been both as hyper-vigilant and using the same PCR-based tools as we are in this pandemic,’ he said.  
 
‘We also need to see testing for other viruses in patients who have reportedly become ill “again”. SARS-CoV-2 is not the only infectious pathogen in town.
 
‘Other infections may start new clinical illnesses as a COVID-19 patient is still shedding the last RNA remnants of SARSV-CoV-2.’
 
When it comes to other strains of coronavirus, infected patients have been observed to produce antibodies that give them immunity varying between months and years. But data on COVID-19 is still very limited just months into the current coronavirus outbreak.
 
One recent study published on rhesus macaques monkeys in China (which has yet to be peer-reviewed) suggests a protective immune response does occur; however, more data is needed to understand if this is common in humans.
 
Meanwhile, the WHO has said it is aware of reported individuals testing negative for COVID-19 and testing positive again days later, and that it is conducting its own investigations.
 
‘We are closely liaising with our clinical experts and working hard to get more information on those individual cases,’ the WHO told Reuters.
 
‘It is important to make sure that when samples are collected for testing on suspected patients, procedures are followed properly.’
 
The number of global coronavirus cases stood at almost two million people, and 126,753 deaths, at the time of publication on Wednesday 15 April.
 
Unlike other countries, Australia has yet to experience widespread community transmission of the virus and appears to be flattening the curve thanks largely to level three restrictions involving stringent social distancing measures.
 
The RACGP has more information on coronavirus available on its website.
 
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