Angola's yellow fever outbreak remains highly concerning, with the disease still maintaining a foothold in hard-hit, highly populated Luanda district, despite the fact that more than 7 million people have now been vaccinated, the World Health Organization (WHO) said yesterday in its weekly update on the situation.
Local yellow fever transmission in under way in six of Angola's other highly populated provinces, with the mosquito-borne disease spreading to new provinces and districts, according to the WHO. Weak surveillance systems are struggling with identifying newly affected areas, especially in remote locations such as Cabinda province.
A related outbreak in urban areas of neighboring Democratic Republic of Congo (DRC) underscores the threat of international spread, especially to Namibia and Zambia where borders are porous and populations aren't usually vaccinated against yellow fever, the WHO said.
New developments since last week's report include confirmed cases and local spread in Angola's Namibe province, which borders Namibia. At the end of April, Namibia reported a suspected yellow fever case imported from Angola, but the patient tested negative for the disease on May 6. Namibia has requested 450,000 doses of yellow fever vaccine to use for travelers and refugees.
DRC, Uganda vaccination efforts
In DRC, 2.2 million doses of vaccine are set to arrive by the middle of May, with immunization campaigns targeted to parts of Kongo and Kinshasa provinces, according to the WHO.
Also, the WHO said the DRC has reported imported cases from two Angolan provinces where local transmission hasn't been reported: Cabinda and Zaire. Cabinda is separated from the rest of Angola by a narrow strip of land belonging to DRC, and the spread of yellow fever there threatens both DRC and the Republic of Congo, the province's neighbor to the north.
In Uganda, where a yellow fever outbreak is under way that isn't linked to Angola, the WHO said that, as of May 11, 51 suspected cases have been reported in seven districts, with 7 lab-confirmed cases in three districts. It added that 700,000 doses of yellow fever vaccine have arrived in the country for an immunization campaign that starts May 19.
Shift in affected African regions
In a backgrounder Q and A report yesterday on Angola's outbreak, the WHO said the location of Africa's yellow fever outbreaks since 2010 has shifted from West Africa—where vaccination programs have has made significant progress with disease control—to central and East Africa, where no mass immunization campaigns have been conducted.
Though yellow fever in Angola is endemic, the outbreak is its first since 1988, when the country registered 37 cases and 14 deaths.
Given the limited supply of vaccine, the WHO said shipments typically meant for routine immunization in endemic countries have been temporarily prioritized to the three outbreak countries and that it and partners are working with prequalified vaccine makers to increase global production.
The WHO said it is looking at ways to stretch the limited supply. Approved vaccines are more potent than required, and clinical studies have shown that using the doses more sparingly could present an option. "Experts are exploring both the feasibility of this option, and the circumstances in which it could be used," the WHO added.
May 12 WHO yellow fever situation report
May 12 WHO Q and A backgrounder