Some people who get sick with kovat 19 are asymptomatic meaning they don’t feel any symptoms of the disease but the infection is still there in a new study published in Nature Medicine last month researchers compared what happens in the bodies of people with both symptomatic and asymptomatic infections and it turns out that not having symptoms of kovat 19 doesn’t mean your body isn’t affected there’s a lot we don’t know about asymptomatic infections including how common they are you won’t know the real number until all this is over but some studies have estimated that it might be around 35 to 40 percent of cases.
So we really want to know what if anything happens to people in these situations in the new study researchers in China looked at 37 people who tested positive for kovat 19 and had mild symptoms as well as 37 people who tested positive but didn’t have any symptoms and even if it wasn’t obvious from the outside that the asymptomatic patients were sick for most of them you could easily tell by looking at their lungs of the 37 patients in that group 21 had abnormal chest CT scans 11 of them with the ground glass texture that’s characteristic of kovat 19 even though they felt fine the team also confirmed that people who are asymptomatic can still be shedding virus particles all over the place in fact they tended to do it for longer than people who did have symptoms that’s troubling because we haven’t ruled out the idea that asymptomatic people can spread the disease and a longer period of viral shedding could mean that not only are they contagious they’re contagious for longer or not you see these particles aren’t necessarily infectious the tests scientists use to detect viral shedding don’t differentiate between broken down bits of old virus in your snot and fully capable viruses that can go on to infect others.
So that’s one thing that could definitely use some more research because we need to pin down how infectious sick people are whether they’re symptomatic or not beyond that though the team also looked at the immune responses of patients in both groups now we don’t yet know for sure if having kovat 19 makes you immune to getting it again even if it does we don’t know how long that immunity lasts but what the study found doesn’t exactly build confidence they found that three to four weeks after their initial exposure to the virus most patients in both groups tested positive for antibodies to the virus the study looked at several types of antibody one of which was AGG the most common kind though the symptomatic patients had much higher levels then eight weeks after they were all released from the hospital that was still true those who had been symptomatic had higher levels of IgG but levels had fallen substantially in nearly all patients in 12 of the patients who had been asymptomatic.
You couldn’t detect these antibodies at all anymore the same was true for only four of the people who had had symptoms so at least among these 74 people some antibody levels seemed to drop within a few months of being infected and in those who didn’t have symptoms they were more likely to drop below what we can detect that’s not super promising it’s too early to say though that asymptomatic cases are at risk of getting infected again we simply don’t know if reinfection is a thing yet and when it comes to immunity these circulating antibodies aren’t the whole story.
For example, we might need to consider memory b-cells those are the kind of immune cells that produce antibodies and they can produce more in response to a repeat infection of the virus even if the person didn’t have many antibodies circulating in their blood when they were reexpose so even if asymptomatic patients do lose more of certain types of antibodies we don’t yet know what that means for their immunity the good news is that a strategy is showing up that may help us detect more asymptomatic cases and it’s cheaper to boot to work around is math it’s an approach you may have heard referred to as pooled or batch testing say you have nasal swabs from 60 people you need to test two of them are positive although you don’t know that yet normally you test each of those swabs individually end up with two positive results and you’re done but you’ve just used up 60 tests another approach would be to pool the swabs together and to say 12 groups of 5 then test each group then you test each individual swab in any group that comes back positive even if the two positive swabs ended up in different groups.
You’d still be using only 22 tests the first round of 12 and going back for 10 individual samples when researchers from Nebraska conducted a study on this and presented the results to the US Food and Drug Administration the organization responded that they wouldn’t object to it basically tacit permission for this approach to move ahead other researchers have proposed ways to get real fancy with the math using computer algorithms asically optimizing the number of tests that are carried out and narrowing down which samples in a pool positive those proposals need to pass peer review but pooled testing isn’t a new strategy it’s been in use since at least the 1940s if it’s used this could help us get more bang for our buck we’re testing resources are limited but these tests still won’t tell us who’s contagious and that’s something that we really need to figure out to make the best decisions about who needs to stay home still we’re learning more and more about what this disease looks like even in people who aren’t aware they’re sick and hopefully we’ll be able to use that knowledge to beat it thanks for watching this episode of scishow if you want to help us bring more informative videos like this one to the public consider supporting us on patreon patrons get access to cool perks like our community discord and exclusive behind-the-scenes materials so check it out to get started head over to patreon.com/scishow.