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WHO: Yellow fever outbreak concerning, but not a global emergency

A female Aedes aegypti mosquito. Credit: Sanofi Pasteur/flickr

The World Health Organization (WHO) declined to classify the ongoing yellow fever outbreak in Angola and the Democratic Republic of the Congo as a public health emergency. Rather, the U.N. health body characterized the outbreak, which has killed nearly 300 people, as a matter that is “serious and of great concern.”

“We determined that the outbreak does not constitute a public health emergency of international concern,” said Oyewale Tomori, the chairman of the emergency committee, in a news conference on Thursday. “However, the seriousness of what is going on could lead to the potential spread [of yellow fever].”

The head of the WHO convened the emergency committee to evaluate the outbreak that started in Angola in December 2015. Cases of the mosquito-born infection spread from the country to neighboring Democratic Republic of the Congo, as well as Uganda, Kenya and China. The committee’s determination, while acknowledging that the outbreak is very serious for the region, shows that it doesn’t believe the yellow fever outbreak has reached the same level of concern globally as the Zika or Ebola outbreaks.

Yellow fever used to be an extremely deadly disease around the world. Vaccines developed nearly a century ago helped eradicate it from most countries and reduced the number of cases worldwide. Today, there are as many as 170,000 cases of yellow fever each year. Of those cases, anywhere between 30,000 and 60,000 are fatal. While yellow fever is found in 47 countries across Africa and Central and South America, the overwhelming majority of cases occur in Africa.

Urban settings with lots of mosquitoes are favorable settings for the spread of yellow fever. Fortunately, the yellow fever vaccine is very effective. A campaign, which started a decade ago, to vaccinate 105 million people against yellow fever in West Africa succeeded in eliminating major outbreaks in the region. To stop the current outbreak in its tracks, international and local health officials are mobilizing to track cases and vaccinate people against yellow fever in Angola and the DRC.

In addition to the immediate consequences of the outbreak, there are broader concerns that it could spread well beyond the currently affected countries. Foreign workers who traveled through Angola have spread yellow fever to China, Uganda and Kenya. While it is not as much of a concern for countries where yellow fever vaccines are regularly given, places like China are vulnerable because virtually nobody is vaccinated against the virus, which is not a public health issue there.

That was the main reason for the emergency meeting. Similar to the fears about Ebola spreading, yellow fever could do the same and may, in fact, infect people more easily. In many ways, it is similar to the rapid spread of Zika emanating from Latin America. The current outbreak is relatively small, but it could spread quickly.

Yellow fever is carried by the Aedes aegypti mosquito, the same one that can harbor dengue and Zika. The mosquitoes are also found in the southern region of the United States, and travelers from Brazil or Angola could import and potentially spread those diseases across the region.

Concerns remain that it could mirror the spread of Ebola in West Africa, where a slow international response coupled with poor health systems in affected countries, led the outbreak to spiral out of control.

“I don’t think we should dismiss the potential worst-case scenario of this epidemic,” Bart Janssens, director of operations for Doctors without Borders, told the Associated Press. “It’s a very unusual situation.”

The number of suspected and confirmed yellow fever cases in Angola are down after peaking seven weeks ago, according to the latest WHO estimates. A concerted push to vaccinate more people in the capital city of Luanda and other affected regions may be enough to end the current outbreak. Some 11.7 million doses of the yellow fever vaccine have been shipped to Angola, and 2.2 million vaccines and ancillaries will arrive in the DRC by the middle of the month.

Neighboring countries Namibia and Zambia, both still unaffected by the outbreak, are taking precautionary measures by requesting more vaccine doses to reach anyone not vaccinated against yellow fever.


About Author

Tom Murphy

Tom Murphy is a New Hampshire-based reporter for Humanosphere. Before joining Humanosphere, Tom founded and edited the aid blog A View From the Cave. His work has appeared in Foreign Policy, the Huffington Post, the Guardian, GlobalPost and Christian Science Monitor. He tweets at @viewfromthecave. Contact him at tmurphy[at]