Lung inflammation and scarring are associated with long COVID
Years after children with measles recover , they can still develop subacute sclerosing panencephalitis ( SSPE ), a deadly brain disorder that is rare in countries with strong immunisation programmes against the disease . Though the measles virus can ’ t be detected in children with SSPE while they ’ re alive , said Dr Nath , bits of viral particles are found in their brains at autopsy .
Similarly , DNA fragments of SARS-CoV-2 have been detected in the intestines of asymptomatic people months after they recovered from COVID-19 . In a more telling sign , Dr David Putrino , director of rehabilitation innovation at the Mount Sinai Hospital in New York , told the Economist that viral material was present in stool samples of some patients treated at his long COVID clinic .
In Dr Nath ’ s view , the theory of viral persistence is reinforced by the observation that most people with long COVID experience mild infections that don ’ t require medical care and only later do they fall ill with long-term problems . Patients with COVID-19 who mount a very strong immune response are more likely to end up in a hospital because their immune cells produce tissue inflammation to get rid of the virus , he argued . But “ if you don ’ t mount a very strong immune response and you ’ re at home with mild symptoms it ’ s possible that you never get rid of the virus completely , and you can have a persistent viral replication going on ,” he posited .
The second hypothesis on the causes of long COVID holds that , though the virus has been completely wiped out , it has nonetheless managed to disrupt the immune system up to a point where it is chronically activated and doesn ’ t know how to shut down .
Dr Chung believes this theory can explain why some people with long COVID develop POTS-like
symptoms . “ There ’ s strong suspicion this could be a sort of autoimmune disease ,” he said .
Following a COVID-19 infection , the body forms antibodies ( proteins produced by the immune system ) that recognise and attack the virus , he explained , but in some cases these proteins can mistakenly target our own tissues , thus inflaming the nerves , for instance , and causing problems .
These rogue autoantibodies have been identified in some patients who got infected with COVID-19 , but it ’ s still unclear whether they ’ re a key driver of long-lasting symptoms associated with the infection .
As for lung damage in patients with long COVID , however , it seems likely that autoimmunity sets in motion a pathological process that could resolve itself without causing significant problems or leading to serious conditions . Lung inflammation is driven by the immune system in its response to COVID infection , said Dr Jenkins , but genetic and lifestyle factors ( including smoking and air pollution ) can increase the risk that this inflammatory process results in long-term lung scarring .
While research is moving forward , both hypotheses might turn out to be accurate for explaining the multiple pathological mechanisms that go under the name of long COVID as well as those behind other syndromes associated with infections , in particular ME / CFS , POTS , and fibromyalgia .
“ It ’ s possible that COVID-19 triggers pathological mechanisms that are common in all these conditions ,” said Dr Nath , hinting that disparate pathogens can cause similar disruptive processes .
If that ’ s the case , the spotlight on COVID-19 might have positive ripple effects for many less-talked about syndromes , setting in motion research that will benefit a variety of other patients suffering from other longterm infections .
DNA fragments of SARS-CoV-2 have been detected in the intestines of asymptomatic people months after they recovered from COVID-19 .
GlobalHealthAsiaPacific . com JUNE 2021
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