A Bangladeshi doctor has allegedly caught coronavirus three times, according to local reports that would mark a world-first.
The medic — referred to only as Dr Das — is said to have caught the disease in the first instance in April while on the frontlines of the epidemic.
After beating the illness and returning to work, he then developed a fever, loss of appetite and aches in July, media in Bangladesh claimed. He isolated at home for seven days and was allowed to return to work following a negative test that proved he had cleared his illness.
The doctor’s coronavirus symptoms then appeared again in the second week of October, and a positive test confirmed it was the viral disease.
Some scientific advisers speculated that the virus had laid dormant in his body for months, causing his three repeat infections — but this has never been proven with Covid.
But British experts have warned the report is likely to be ‘nonsense’, saying details on whether or not the three strains were genetically different — the only way of proving it was a re-infection — were not reported.
A doctor in Bangladesh claims to have caught coronavirus three times, according to local reports that would mark a world-first. Re-infections have been reported in the Netherlands, Hong Kong, Belgium, and the US
However, research is starting to mount that immunity against the coronavirus may only last a short period of time, and therefore a person can catch it repeatedly like the common cold or flu.
The largest study on Covid-19 immunity — published by British researchers yesterday — suggested reinfection can occur between six to 12 months after beating Covid the first time.
While it’s possible to catch the disease a second time, scientists agree it’s unlikely to happen within a year.
People with weaker immune systems — such as the elderly — struggle to make large amounts of antibodies, disease-fighting proteins found in blood that store memories of how to fight off specific viruses.
In vulnerable and elderly people antibodies often fade quicker, meaning they lose any protection they had developed against Covid-19.
Details about the Bangladeshi case are scarce but have been picked up widely by Chinese media.
It’s unclear how old Dr Das is or whether he had any underlying illnesses — but his profession would have seen him exposed to the virus.
Local media outlets reported that Dr Das had suffered symptoms on three separate occasions — in April, July and October.
According to the China Central Television news website, citing a local newspaper in Bangladesh, 25 people in Bangladesh have been re-infected with Covid.
Dr A.S.M. Alamgir, senior scientific officer at the Institute of Epidemiology Disease Control and Research in Bangladesh, told the Global Times that within six months of the first infection, the virus may become dormant in a patient’s body and cause a second infection.
However, Wang Peiyu, deputy head of Peking University’s School of Public Health, China, suggested that the man’s immunity to the coronavirus faded, and so it was possible he could be re-infected again.
Dr Peiyu said: ‘This is a rare case, and there are two possible reasons: one is that the person’s immune system and resistance is weak, so the antibody stays in the body for too short a time, leading to a third infection.
‘The second possibility might be that the virus has undergone a greater degree of mutation, and the antibodies originally produced are no longer sufficient to resist the virus.’
Dr Peiyu said this situation was ‘unlikely to happen in China’, but did not expand on why.
Dr David Strain, a clinical senior lecturer, University of Exeter and chair of the British Medical Association’s Medical Academic Staff Committee, said that reinfection was entirely possible.
But he is dubious of the details in this report. He told MailOnline that case was likely to be ‘nonsense’.
And he said it is not clear whether he had three separate infections, or whether tests spotted dead fragments of the virus multiple times.
Hundreds of supposed cases of reinfection in South Korea and China early in the crisis were proven to be false positives caused by dead viral particles.
PCR tests – which amplify people’s genetics to hunt for parts of the disease – are sometimes so accurate they spot tiny remnants of virus from previous infection.
These tests cannot distinguish whether the virus detected in people’s bodies is dead or alive, and can therefore lead to false positives.
However, this would not explain why the Bangladeshi doctor fell ill on three separate occasions. A dead virus is unlikely to have cause him illness.
Dr Strain added: ‘It is entirely possible he was just carrying the virus that one of his patients had presented with. It’s not a “false positive” per say, but that’s probably the closest description.
‘He probably had [viral particles] in his mouth and then tested positive.
‘Even if he did not get significant infection but was little more than a carrier the second and third time, the fact that he was carrying the virus means he may have been infectious to his patients.’
A true re-infection requires genetic testing to see whether the two instances of the virus differ slightly.
Dr Strain said: ‘Getting genetic testing on early infections was, and is, pretty difficult in Exeter with a genetic lab looking at specific geneotypes, let alone in a not particularly well resourced place like Bangladesh.
‘The general view is we can get a cold or the flu more than once, so there is no reason you can’t get this virus more than once.’
Dr Jeffrey Barrett, of the COVID-19 Genome Project at the Wellcome Sanger Institute, told MailOnline: ‘This report does not indicate that the virus genome was sequenced from any of the different positive tests, which makes it hard to confirm three repeat infections. Some people can be sick for months after a single infection.
‘There have been over 100million cases of Covid-19 around the world, and since we are seeing only a small number of fully confirmed reports of re-infection, it seems to be rare to be infected twice (or more) in the space of a few months.
‘What we don’t know yet is whether people might be infected multiple times over much longer time scales, like years.’
It comes after a Government-led study on Tuesday found 26 per cent fewer Britons have coronavirus antibodies now than at the peak of the first wave.
It raised concerns that protection against the disease is short-lived and that people may be able to get reinfected just months after recovering the first time.
Imperial College London scientists, who led the research, said they suspect natural protection against Covid-19 lasts between six to 12 months.
They believe that most people will be vulnerable to reinfection after that time.
Scientists insisted the truth on immunity is still murky and said it was possible that the body could still rapidly produce antibodies in the future, even if someone no longer tests positive for them.
They said this may not protect them entirely but lead to a milder illness.
However, Dr Strain said it could go the other way — in some diseases, illness gets more severe the more times a person is infected, such as with Dengue fever and Ebola.
He said: ‘What I would imagine is your second response is a lot more mild than the first. You’d be back to normal in about 72 hours because your memory cells respond quickly.
‘Older adults would more at risk of getting a second infection because the immune system is slightly weaker.
‘But the other thing we need to be careful of is the younger patients — those in their 50s or 60s — who died due to their overactive immune response to Covid.
‘It is theoretically possible that the second response could be even more aggressive than the first.’
This response has been reported in a 25-year-old American man, one of the handful of cases of re-infection across the globe that have been reported before.
Doctors in the US reported in The Lancet last week of a unnamed man who had two positive tests — one in April and one in June — with two negative tests in-between indicating he recovered from the first bout of illness.
Genetic analysis of the swabs showed ‘significant differences’ between the variants in the viruses DNA, which suggests he was truly infected twice.
The second infection was symptomatically more severe than the first, the doctors in Nevada reported.
The first illness, the man had a sore throat, cough, headache, nausea, and diarrhoea and recovered within 10 days. The second time, he had the same symptoms for five days before getting short of breath and needing oxygen.
It followed the cases of two European Covid-19 survivors who had been re-infected after recovering from the disease.
In some cases, the details of re-infection have been scarce or there is no genetic testing to back up the claims. It may just be a case of faulty testing.
But the cases indicate that previous exposure to SARS-CoV-2 does not necessarily translate to guaranteed total immunity over a long period.
This would make stamping the life-threatening virus out even more challenging because patients that had the coronavirus back in the spring could be re-infected this winter.
The implications of reinfections could be relevant for vaccine development because it may mean people need booster jabs after the first one to offer robust protection.
Dr Strain said: ‘It is obviously worrying regarding the vaccines. If you can get different strains at different time then the vaccine may end up being pointless.
‘It also undermines the herd immunity path that some degree is still being followed.’