Flu may be spread just by breath­ing

A new med­i­cal study out­lines how the con­cen­tra­tion of flu virus in ex­haled breath vastly in­creases the risk of in­fec­tion.

The Standard Journal - - LOCAL & NATIONAL - By Tracy Seipel

A new study re­leased in the Pro­ceed­ings of the Na­tional Academy of Sciences re­veals that we may pass the flu to others just by breath­ing.

The study — which in­cluded re­searchers from San Jose State Uni­ver­sity and UC Berke­ley — pro­vides new ev­i­dence for the po­ten­tial im­por­tance of the flu’s air­borne trans­mis­sion be­cause of the large quan­ti­ties of in­fec­tious virus re­searchers found in the ex­haled breath from peo­ple suf­fer­ing from flu.

“The study find­ings sug­gest that keep­ing sur­faces clean, wash­ing our hands all the time, and avoid­ing peo­ple who are cough­ing does not pro­vide com­plete pro­tec­tion from get­ting the flu,” Sh­eryl Ehrman, dean of the Col­lege of En­gi­neer­ing at San Jose State Uni­ver­sity, said in a state­ment.

“Stay­ing home and out of pub­lic spa­ces could make a dif­fer­ence in the spread of the in­fluenza virus.”

The study was done at the Uni­ver­sity of Mary­land dur­ing the flu sea­son of De­cem­ber 2012 through March 2013. Re­searchers there re­cruited 178 vol­un­teers, mostly stu­dents, who were within the first three days of the flu’s on­set.

Over four months, re­searchers cap­tured and char­ac­ter­ized the flu virus in ex­haled breath from 142 of the vol­un­teers who had con­firmed cases of the flu, as the vol­un­teers breathed nat­u­rally, talked, coughed or sneezed.

The re­searchers then as­sessed the in­fec­tiv­ity of nat­u­rally oc­cur­ring flu aerosols, tiny droplets that stay sus­pended in the air for a long time.

The study said par- tic­i­pants pro­vided 218 swabs from the up­per part of their throats that lies just be­hind the nose, and the same num­ber of 30-minute sam­ples of ex­haled breath, spon­ta­neous cough­ing, and sneez­ing on the first, sec­ond, and third days af­ter the on­set of flu symp­toms.

The analysis of the in­fec­tious virus re­cov­ered from these sam­ples showed that a sig­nif­i­cant num­ber of flu pa­tients rou­tinely shed in­fec­tious virus, not merely de­tectable ri­bonu­cleic acid, or RNA, into aerosol par­ti­cles small enough to present a risk for air­borne trans­mis­sion.

Sur­pris­ingly, the study said, 11 of the 23 fine aerosol sam­ples ac­quired in the ab­sence of cough­ing had de­tectable vi­ral RNA, and 8 of these 11 con­tained in­fec­tious virus, sug­gest­ing that cough­ing was not nec­es­sary for in­fec­tious aerosol gen­er­a­tion in the fine aerosol droplets.

“We found that flu cases con­tam­i­nated the air around them with in­fec­tious virus just by breath­ing, with­out cough­ing or sneez­ing,” Dr. Don­ald Mil­ton, pro­fes­sor of en­vi­ron­men­tal health in the Uni­ver­sity of Mary­land School of Pub­lic Health, said in a state­ment.

The re­searchers be­lieve that their find­ings could be used to im­prove math­e­mat­i­cal mod­els of the risk of air­borne flu trans­mis­sion from peo­ple with flu symp­toms. The re­sults could help de­velop more ef­fec­tive pub­lic health in­ter­ven­tions and to con­trol and re­duce the im­pact of in­fluenza epi­demics and pan­demics.

‘We found that flu cases con­tam­i­nated the air around them with in­fec­tious virus just by breath­ing, with­out cough­ing or sneez­ing.’

Dr. Don­ald Mil­ton

Uni­ver­sity of Mary­land

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