long covid: for the 1 in 10 patients who become long-haulers, covid-19 has lasting effects

we know it generically as “ long covid ,” though it’s hardly generic, and we still know very little about it, including what it is, who, when or how badly it will strike, how long it might take to recover or whether complete recovery is possible for all.

long covid, or post-covid condition,  features symptoms that can include  trouble breathing, chest pain, brain “fog,” fatigue, loss of smell or taste, nausea, anxiety and depression,  among others .

it appears to  affect about one in 10 people  who have recovered from a covid-19 infection.  in canada , a conservative estimate is that long covid has affected 100,000 to 150,000 people so far, although the studies assessing prevalence have serious methodologic flaws.

post-viral syndromes

the medical and research community first became aware of long covid as a sometimes debilitating post-viral syndrome that  first appeared to affect patients who’d had severe covid-19 , particularly those  who had been treated in intensive care .

similar symptoms that follow viral infections other than covid have been seen before.  post-viral syndrome after influenza  continues to haunt some long after the infection has passed, for example. even common and typically less harmful viral infections  such as mononucleosis  can sometimes have very  serious and long-lasting after-effects .

cause and effect

viruses and hosts

the relationship between hosts and viruses can be complex and highly varied. it is  shaped by the condition of a patient prior to being infected, and by the individual’s immune system . the interplay between those factors creates a wide range of potential outcomes, making it harder to study and treat this new condition.

some of long covid’s effects  appear to be caused by inflammation , which is part of the body’s typical reaction to any virus.  this reaction is exaggerated in covid-19 , especially in terms of the immune system’s inability to return to normal function.

when a patient’s body is unable to eliminate a virus quickly, it escalates its immune response, and can end up  making antibodies against itself . some of what we are seeing with long covid may be due to the collateral damage from that response, especially when the inflammation resulting from the acute infection was severe.