we may be a step closer to understanding one of the great mysteries of the covid pandemic and that is why the virus is devastating to some while others who caught it showed no symptoms at all or hardly any symptoms. a new study is shedding light on how genetics may actually play a role. we have medical correspondent meghan terrel joining us to break all of this down. really interesting, because i think everyone looked at people around them, saw the differing levels of symptoms and outcomes people were having. what are researchers learning? this is really fascinating. there were two different studies that really look at the different spectrums of covid, a symptomatic covid, no symptoms at all or long covid. so if we start with a symptomatic covid, here, researchers looked at people based on what form of hla they had, this is human antigens, this is a marker on cells that s important in the immune response and they found that