Deadly bird flu surges in hu­mans

Evolv­ing H7N9 strain poses risk of a pan­demic threat, ex­perts say

The Washington Post Sunday - - POLITICS & THE NATION - BY LENA H. SUN lena.sun@wash­ More at wash­ing­ton­ blogs/to-your-health

A surge in hu­man in­fec­tions of a deadly bird flu in China is prompt­ing in­creas­ing con­cern among health of­fi­cials around the world. Ex­perts are call­ing for con­stant mon­i­tor­ing be­cause of the large in­crease in bird flu cases this sea­son, and be­cause there are wor­ri­some changes in the virus.

U.S. of­fi­cials say that of all emerg­ing in­fluenza viruses, this par­tic­u­lar virus poses the great­est risk of a pan­demic threat if it evolves to spread read­ily from hu­man to hu­man, ac­cord­ing to a re­port re­leased Fri­day.

Cen­ters for Dis­ease Con­trol and Preven­tion of­fi­cials are de­vel­op­ing a vac­cine that would tar­get a newly evolv­ing ver­sion of the virus.

China is ex­pe­ri­enc­ing its largest out­break of the H7N9 bird flu strain, with at least 460 in­fec­tions re­ported since Oc­to­ber. About a third of the peo­ple di­ag­nosed with H7N9 have died of their in­fec­tions, ac­cord­ing to the World Health Or­ga­ni­za­tion. Hu­man in­fec­tions with this type of bird flu were first re­ported in China in March 2013. Since then, there have been yearly epi­demics of hu­man in­fec­tions.

But this win­ter, the num­ber of cases is greater than in any of the pre­vi­ous four sea­sons. This year’s in­fec­tions ac­count for more than a third of the 1,258 H7N9 cases that have been re­ported since 2013. Most hu­man in­fec­tions in­volve ex­po­sure to live poul­try or con­tam­i­nated en­vi­ron­ments, es­pe­cially mar­kets where live birds have been sold. Dur­ing the pre­vi­ous four waves of H7N9, 88 per­cent of pa­tients de­vel­oped pneu­mo­nia, 68 per­cent were ad­mit­ted to an in­ten­sive care unit and 41 per­cent died, ac­cord­ing to a re­port from the CDC.

“This is the virus we were con­cerned about in 2013, and now we’re see­ing th­ese in­creas­ing num­ber of cases,” said Daniel Jerni­gan, who heads the CDC’s in­fluenza divi­sion. “This year it came back much stronger, so the num­ber of cases we’re see­ing has al­ready sur­passed all the other waves, and the sea­son isn’t even over yet.”

In ad­di­tion, the virus has be­come more deadly to poul­try, which might lead to more se­vere in­fec­tions in hu­mans, he said. For all those rea­sons, of­fi­cials are watch­ing de­vel­op­ments closely.

“This is a virus you don’t want to take your eyes off,” Jerni­gan said.

Among a dozen an­i­mal and bird viruses that are not yet cir­cu­lat­ing widely in peo­ple, the H7N9 virus has the great­est po­ten­tial to cause a pan­demic, ac­cord­ing to the CDC. That as­sess­ment is based on the virus’s abil­ity to spread eas­ily and ef­fi­ciently to peo­ple from an­i­mals, and its abil­ity to cause se­ri­ous dis­ease.

On Wed­nes­day, WHO of­fi­cials in Geneva said the risk of sus­tained hu­man-to-hu­man trans­mis­sion of H7N9 re­mains low. The char­ac­ter­is­tics of the in­fec­tions and case fa­tal­ity rate re­main sim­i­lar to those of pre­vi­ous waves, of­fi­cials said.

But “con­stant change is the na­ture of all in­fluenza viruses,” Wen­qing Zhang, who heads the WHO’s global in­fluenza pro­gram, told re­porters dur­ing a me­dia brief­ing Wed­nes­day. “This makes in­fluenza a per­sis­tent and sig­nif­i­cant threat to pub­lic health.”

One change al­ready un­der­way is the virus has split into two dis­tinct ge­netic lin­eages, with a new branch of the virus fam­ily now emerg­ing in the cur­rent epi­demic, of­fi­cials said.

That has ren­dered the H7N9 vac­cine stock­piled by the United States less ef­fec­tive against the newly emerg­ing branch, of­fi­cials said. The CDC is de­vel­op­ing an in­fluenza seed virus that can be used by vac­cine man­u­fac­tur­ers to pro­duce an­other H7N9 vac­cine to match a newly emerg­ing H7N9 strain.

It will take sev­eral months to pro­duce and test a new vac­cine, a process that will get un­der­way in June and July af­ter vac­cine man­u­fac­tur­ers com­plete their work on mak­ing sea­sonal flu vac­cine.

Vac­cines to pro­tect first re­spon­ders against the high­est-risk bird flu viruses are part of the pan­demic flu stock­pile main­tained by the Biomed­i­cal Ad­vanced Re­search and De­vel­op­ment Au­thor­ity, the agency within the Depart­ment of Health and Hu­man Ser­vices re­spon­si­ble for pro­vid­ing med­i­cal coun­ter­mea­sures to hu­man-made and nat­u­ral threats, in­clud­ing pan­demic in­fluenza and emerg­ing in­fec­tious dis­eases.

Rick Bright, di­rec­tor of BARDA, said man­u­fac­tur­ers will be pro­duc­ing enough vac­cine to pro­vide 40 mil­lion doses, enough to vac­ci­nate 20 mil­lion peo­ple.


A med­i­cal team treats an H7N9 bird flu pa­tient in Wuhan, China, last month. The coun­try is fac­ing its largest out­break of the virus.

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