The Pan Amer­i­can Health Or­ga­ni­za­tion (PA­HO) has is­sued a new Rapid Risk As­sess­ment (RRA) on yel­low fever in the Amer­i­c­as—in­clud­ing the Caribbean—which it said shows that the risk to pub­lic health re­mains high due to con­tin­ued hu­man cas­es in en­dem­ic coun­tries of the re­gion.

PA­HO said that so far this year, there has been a more than 8-fold in­crease in cas­es com­pared to the same pe­ri­od of 2024.

It said this is due to the pe­ri­od­ic re­ac­ti­va­tion of syl­vat­ic trans­mis­sion cy­cles with spillover cas­es among peo­ple and that in to­tal, coun­tries have re­port­ed 221 con­firmed hu­man cas­es of yel­low fever, in­clud­ing 89 deaths.

In com­par­i­son, in 2024, there were 61 hu­man cas­es con­firmed, in­clud­ing 30 deaths.

PA­HO said that of con­cern is the fact that while in 2024 most cas­es were re­port­ed in the Ama­zon re­gion of Bo­livia, Brazil, Colom­bia, Guyana, and Pe­ru, this year, cas­es have al­so been re­port­ed out­side the Ama­zon re­gion in ar­eas such as Sao Paulo State in Brazil and Toli­ma De­part­ment in Colom­bia.

It said syl­vat­ic yel­low fever oc­cur­rence near dense­ly pop­u­lat­ed ar­eas in­creas­es the risk of an ur­ban out­break.

“Al­most all cas­es re­port­ed in both 2024 and 2025 have oc­curred in un­vac­ci­nat­ed in­di­vid­u­als,” PA­HO re­port­ed. “Pri­or to the COVID-19 pan­dem­ic, vac­ci­na­tion cov­er­age against yel­low fever in en­dem­ic coun­tries of the re­gion ranged from 57 per cent to 100 per cent among chil­dren aged 9-18 months.”

“How­ev­er, 10 out of 12 en­dem­ic coun­tries had cov­er­age rates be­low the rec­om­mend­ed 95 per cent. Be­tween 2020-2023, these rates de­clined fur­ther, leav­ing a sub­stan­tial pro­por­tion of the pop­u­la­tion un­pro­tect­ed,” PA­HO said,

PA­HO not­ed that while vac­ci­na­tion ca­pac­i­ties in en­dem­ic coun­tries have since im­proved, the lim­it­ed glob­al sup­ply of yel­low fever vac­cines con­tin­ues to pose a chal­lenge, with cur­rent sup­plies un­able to cov­er de­mand in the Amer­i­c­as and in Africa.

In the risk as­sess­ment, PA­HO calls for the need to strength­en sur­veil­lance, vac­ci­na­tion of at-risk pop­u­la­tions, and com­mu­ni­ca­tion strate­gies to en­sure the pro­vi­sion of pub­lic health ad­vice for af­fect­ed com­mu­ni­ties and those trav­el­ling to ar­eas where vac­ci­na­tion is rec­om­mend­ed.

PA­HO said it is al­so work­ing with en­dem­ic coun­tries to pro­vide tech­ni­cal sup­port aimed at op­ti­miz­ing vac­ci­na­tion strate­gies. This in­cludes the use of frac­tion­al dos­es where ap­pro­pri­ate and iden­ti­fy­ing pop­u­la­tions most at risk and in great­est need of vac­ci­na­tion.

Yel­low fever is an acute haem­or­rhag­ic dis­ease that is en­dem­ic in trop­i­cal ar­eas of the Amer­i­c­as and Africa. In the Amer­i­c­as, it is com­mon­ly trans­mit­ted by syl­vat­ic mos­qui­toes be­long­ing to the Haemogogus and Sa­bethes species.

Symp­toms usu­al­ly ap­pear three to six days af­ter the bite of an in­fect­ed mos­qui­to and in­clude fever, mus­cle pain, headache, shiv­ers, loss of ap­petite, nau­sea and vom­it­ing. While most pa­tients’ symp­toms dis­ap­pear, around 15 per cent ex­pe­ri­ence high fever, or­gan dam­age and some­times death.

PA­HO said it con­tin­ues to mon­i­tor the sit­u­a­tion and sup­port coun­tries in adopt­ing the best strate­gies for pre­vent­ing and re­spond­ing to yel­low fever out­breaks. —WASH­ING­TON D.C. (CMC)