Achoo! The dis­tance germs can travel is noth­ing to sneeze at

The Hamilton Spectator - - HEALTH - AL­LIE SHAH

We all do it. Some of us do it quite loudly. Oth­ers do it not once, but sev­eral times in a row.

The cho­rus of achoos in of­fices, on buses and in homes of­ten sends by­standers scram­bling to get out of the line of germ-spread­ing fire. But how far is far enough away to avoid get­ting hit by a snot-and-fluid pro­jec­tile? A lot far­ther than you might — or would like to — think. We’re talk­ing 20 feet or more.

Re­cent re­search, how­ever, of­fers new in­sights on the sci­ence of sneez­ing — re­veal­ing what hap­pens when we sneeze and how far the spray of saliva and mu­cus can travel.

A sneeze is a re­flex re­ac­tion, ex­plained Dr. Scott Davies, a physi­cian at Hen­nepin County Med­i­cal Cen­ter in down­town Min­neapo­lis who spe­cial­izes in treat­ing res­pi­ra­tory dis­eases. It hap­pens when re­cep­tors in the nose de­tect ir­ri­tants. It can be an odour, such as per­fume or smoke. It can be pollen in the air or pet dan­der — any type of al­ler­gen, re­ally. For some peo­ple, cold air or sun­light can trig­ger the sneeze re­flex. Once the nose re­cep­tors sense the ir­ri­tant, the brain re­ceives a sig­nal and the body re­sponds in­vol­un­tar­ily.

“That re­flex trig­gers a vi­o­lent re­ac­tion that in­volves your neck, the chest, the ab­domen, the di­aphragm,” Davies said. “You cre­ate this force­ful blast of air through your nose.”

The air comes from your lungs, and there’s a deep in­hale just be­fore the sneeze to pro­duce a large gust of air. So what pur­pose does sneez­ing serve? Cleans­ing, said Jeanne Pfeif­fer, an as­so­ciate pro­fes­sor at the Univer­sity of Min­nesota School of Nurs­ing and long­time ex­pert in in­fec­tion pre­ven­tion and con­trol. Think of it as your body spot­ting a squat­ter in the nose that needs to be evicted. The more some­one sneezes, the more likely that pesky free­loader is still there. Hold the pep­per.

Sneez­ing helps re­set the en­vi­ron­ment in­side the nose, al­low­ing trou­ble­some par­ti­cles in­haled through the nose to be­come trapped in the mu­cus lin­ing, ac­cord­ing to a re­cent study con­ducted by re­searchers at the Univer­sity of Penn­syl­va­nia in Philadel­phia.

For a long time, peo­ple on the front lines of sneeze sci­ence thought that the droplets scat­tered from a sneeze trav­elled only a short dis­tance — a cou­ple of feet, per­haps. But a slow­mo­tion video of a sneeze cap­tured re­cently by Mas­sachusetts In­sti­tute of Tech­nol­ogy (MIT) re­searchers un­cov­ered a far more trou­bling truth: Those sneeze par­ti­cles can go mighty far.

The video shows in gross de­tail what hap­pens to the liq­uid mix­ture spewed from a per­son’s mouth and nose dur­ing a sneeze.

The find­ings, as de­scribed by MIT re­searchers in the New Eng­land Jour­nal of Medicine, show that the droplets spread far­ther than pre­vi­ously thought — aided by a swirling puff cloud.

“The largest droplets rapidly set­tle within about 3 to 6 feet away from the per­son,” wrote lead re­searcher Ly­dia Bourouiba, of MIT’s Fluid Dy­nam­ics and Dis­ease Trans­mis­sion Lab­o­ra­tory. “The smaller and evap­o­rat­ing droplets are trapped in the tur­bu­lent puff cloud, re­main sus­pended, and, over the course of sec­onds to a few min­utes, can travel the di­men­sions of a room and land up to 19 to 26 feet away.”

So what, then, is your best de­fence against con­tam­i­na­tion from a nearby sneeze cloud?

“It’s up to the per­son who’s sneez­ing to pre­vent this,” Davies said.

Back in the day, dis­ease pre­ven­tion gu­rus taught us to cover our mouths with our hands when we felt a sneeze com­ing on. That method, while bet­ter than an open-mouthed sneeze, is no longer the pre­ferred method. That’s be­cause once your hand is wet and germy, it is easy to trans­fer those germs to sur­faces such as key­boards, pens and door­knobs — spread­ing sick­ness from per­son to per­son.

Pfeif­fer and other health pro­fes­sion­als now rec­om­mend sneez­ing into a tis­sue or into our el­bow.

Sneezes can travel as fast as 100 miles per hour, by some es­ti­mates. And the force of a sneeze? Well, that’s noth­ing to sneeze at, ei­ther. Davies said while it’s ex­tremely rare, some peo­ple have even been in­jured from sneez­ing hard.

“You can break a rib sneez­ing,” he said.


The more some­one sneezes, the more likely a pesky ir­ri­tant — an odour, pollen, per­fume, smoke — is still in the nose. Sneez­ing helps re­set the nasal en­vi­ron­ment.

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