tonight for a growing number of Americans this summer of sizzling temps is also the summer of sick the number of covid cases now on the rise Nationwide so far 15 states have hire very high levels of the virus in their Wastewater according to the latest data released by the CDC I I probably characterize it more as a swell um it's certainly more than we've seen in the last few months as people crowd indoors to escape the heat the virus spreads this year's uptick is thanks to the so-called flirt variants subvariants of Omron which now account for more than 60% of covid cases covid-19 is indeed becoming uh more mild over time population immunity has been going up and therefore the severity of the illness has been going down and yet it's still worse than the flu yes covid-19 is still worse than the flu the outcomes of covid-19 are still worse than the flu doctors say the elderly and imuno compromised are still at high risk of severe disease and should consider masking in public spaces and make sure they're up to date on their vaccines while preventative masking for healthy individuals is no longer recommended by the CDC they say if you're infected wearing a mask can prevent spread as for isolating the CDC has updated their guidance saying that if you have symptoms stay isolated otherwise you don't need to isolate even if you're testing positive that new guidance has raised some concern among medical experts Lester thanks for watching stay updated about breaking news and top stories on the NBC News app or follow us on social media