Dr. Margaret Chan, director-general of the World Health Organization, visited Angola on April 4 for a two-day visit to assess the yellow fever outbreak there. Photo by Jose Caetano/WHO

WASHINGTON, April 12 (UPI) -- An outbreak of yellow fever that started in December in Angola is spreading, with the number of cases and deaths in the Democratic Republic of the Congo rising and individuals who have picked up the infection in Angola showing up in other countries, according to new reports.

The World Health Organization reports 151 cases of yellow fever and 21 deaths in Congo as of March 22, an expansion of the outbreak in Angola that has sickened 450 and killed 225 since last year -- which has health officials around the world scrambling to stop what they say is a dangerous situation.


"You think SARS was bad?," Dr. Duane Gubler, a researcher at the WHO and director of the emerging infectious disease program at the Duke University-National University of Singapore Graduate Medical School, told STAT. "This would make it pale by comparison."

Although case numbers in Angola have fallen, experts are sounding the alarm that the outbreak could get much worse if it spreads, a potentially larger issue as the WHO has sent its entire vaccine reserve to the country.

Angolan officials asked the WHO to send enough of the vaccine for the country's 7.2 million citizens, though the international organization's stockpile has about six million doses -- short of what Angola needs, before considering any other country.

WHO officials, while speaking positively about the effects of vaccination and other efforts to prevent the spread of yellow fever, have asked leaders in Angola to pause the widespread vaccination until the stockpile can be replenished. About 5.4 million Angolan citizens already have received the vaccine.

"The vaccination campaign has so far been effective," Dr. Sergio Yactayo, expert on epidemic diseases at the WHO, said in a press release. "We are seeing case numbers dropping considerably, especially in Luanda. We need to vaccinate the maximum number of people in Luanda and the affected provinces as possible to stop the spread of this deadly disease."

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WHO officials say they are working with governments and manufacturers to divert vaccine shipments and boost production in order to replenish the emergency stockpile.

Yellow fever is spread by mosquitoes, including the Aedes aegypti that also spread the Zika virus, causing fever, headache, muscle pain, nausea, vomiting and fatigue. For most people, symptoms disappear in a few days. For some, a "toxic" phase that gets significantly worse kills about half these patients within two weeks.