U.S. pub­lic health of­fi­cials have been told to stop work­ing with the World Health Or­ga­ni­za­tion, ef­fec­tive im­me­di­ate­ly.

A U.S. Cen­ters for Dis­ease Con­trol and Pre­ven­tion of­fi­cial, John Nken­ga­song, sent a memo to se­nior lead­ers at the agency on Sun­day night telling them that all agency staff who work with the WHO must im­me­di­ate­ly stop their col­lab­o­ra­tions and “await fur­ther guid­ance.”

Ex­perts said the sud­den stop­page was a sur­prise and would set back work on in­ves­ti­gat­ing and try­ing to stop out­breaks of Mar­burg virus and mpox in Africa, as well as brew­ing threats from around the world. It al­so comes as health au­thor­i­ties around the world are mon­i­tor­ing bird flu out­breaks among U.S. live­stock.

The As­so­ci­at­ed Press viewed a copy of Nken­ga­song’s memo, which said the stop-work pol­i­cy ap­plied to “all CDC staff en­gag­ing with WHO through tech­ni­cal work­ing groups, co­or­di­nat­ing cen­ters, ad­vi­so­ry boards, co­op­er­a­tive agree­ments or oth­er means — in per­son or vir­tu­al.” It al­so says CDC staff are not al­lowed to vis­it WHO of­fices.

Pres­i­dent Trump last week is­sued an ex­ec­u­tive or­der to be­gin the process of with­draw­ing the U.S. from WHO, but that did not take im­me­di­ate ef­fect. Leav­ing WHO re­quires the ap­proval of Con­gress and that the U.S. meets its fi­nan­cial oblig­a­tions for the cur­rent fis­cal year. The U.S. al­so must pro­vide a one-year no­tice.

His ad­min­is­tra­tion al­so told fed­er­al health agen­cies to stop most com­mu­ni­ca­tions with the pub­lic through at least the end of the month.

“Stop­ping com­mu­ni­ca­tions and meet­ings with WHO is a big prob­lem,” said Dr. Jef­frey Klaus­ner, a Uni­ver­si­ty of South­ern Cal­i­for­nia pub­lic health ex­pert who col­lab­o­rates with WHO on work against sex­u­al­ly trans­mit­ted in­fec­tions.

“Peo­ple thought there would be a slow with­draw­al. This has re­al­ly caught every­one with their pants down,” said Klaus­ner, who said he learned of it from some­one at CDC.

“Talk­ing to WHO is a two-way street,” he added, not­ing that WHO and U.S. health of­fi­cials ben­e­fit from each oth­er’s ex­per­tise. The col­lab­o­ra­tion al­lows the U.S. to learn about new tests and treat­ments as well as about emerg­ing out­breaks — in­for­ma­tion “which can help us pro­tect Amer­i­cans abroad and at home.”

A U.S. health of­fi­cial, who was not au­tho­rized to talk about the memo and spoke on con­di­tion of anonymi­ty, con­firmed the stop­page.

A WHO spokesper­son re­ferred ques­tions about the with­draw­al to U.S. of­fi­cials.

Of­fi­cials at the U.S. De­part­ment of Health and Hu­man Ser­vices didn’t im­me­di­ate­ly re­spond to an emailed re­quest for com­ment.

The As­so­ci­at­ed Press Health and Sci­ence De­part­ment re­ceives sup­port from the Howard Hugh­es Med­ical In­sti­tute’s Sci­ence and Ed­u­ca­tion­al Me­dia Group and the Robert Wood John­son Foun­da­tion. The AP is sole­ly re­spon­si­ble for all con­tent.

By MIKE STO­BBE

NEW YORK (AP)