Tiny air­borne par­ti­cles pose big coro­n­avirus risk

Arab Times - - FRONT PAGE -

NEW YORK, Sept 26, (AP): At a Univer­sity of Mary­land lab, peo­ple in­fected with the new coro­n­avirus take turns sit­ting in a chair and putting their faces into the big end of a large cone. They re­cite the al­pha­bet and sing or just sit qui­etly for a half hour. Some­times they cough.

The cone sucks up ev­ery­thing that comes out of their mouths and noses. It’s part of a de­vice called “Ge­sund­heit II” that is help­ing sci­en­tists study a big ques­tion: Just how does the virus that causes COVID-19 spread from one per­son to another?

It clearly hitch­hikes on small liq­uid par­ti­cles sprayed out by an in­fected per­son. Peo­ple ex­pel par­ti­cles while cough­ing, sneez­ing, singing, shout­ing, talk­ing and even breath­ing. But the drops come in a wide range of sizes, and sci­en­tists are try­ing to pin down how risky the var­i­ous kinds are.

The an­swer af­fects what we should all be do­ing to avoid get­ting sick. That’s why it was thrust into head­lines a few days ago when a US health agency ap­peared to have shifted its po­si­tion on the is­sue, but later said it had pub­lished new lan­guage in er­ror.

The rec­om­men­da­tion to stay at least 6 feet (2 me­ters) apart – some au­thor­i­ties cite about half that dis­tance – is based on the idea that larger par­ti­cles fall to the ground be­fore they can travel very far. They are like the droplets in a spritz of a win­dow cleaner, and they can in­fect some­body by land­ing on their nose, mouth or eyes, or maybe be­ing in­haled.

But some sci­en­tists are now fo­cus­ing on tinier par­ti­cles, the ones that spread more like cig­a­rette smoke. Those are car­ried by wisps of air and even up­ward drafts caused by the warmth of our bod­ies. They can linger in the air for min­utes to hours, spread­ing through­out a room and build up if ven­ti­la­tion is poor.

The po­ten­tial risk comes from in­hal­ing them. Measles can spread this way, but the new coro­n­avirus is far less con­ta­gious than that.

For th­ese par­ti­cles, called aerosols, “6 feet is not a magic dis­tance,’’ says Lin­sey Marr, a lead­ing re­searcher who is study­ing them at Vir­ginia Tech in Blacks­burg. But she says it’s still im­por­tant to keep one’s dis­tance from oth­ers, “the far­ther the bet­ter,” be­cause aerosols are most con­cen­trated near a source and pose a big­ger risk at close range.

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