Yellow fever is an acute viral hemorrhagic fever spread by Aedes mosquitoes, the same mosquitoes that transmit Zika. The “yellow” refers to the jaundice that affects some patients. Up to half of the severely affected people will die from yellow fever. Yellow fever is endemic in some tropical parts of Africa and Latin America. There is no specific treatment for yellow fever, merely symptomatic treatment, but there is a highly effective vaccine that has been partly responsible for the decreasing number of yellow fever cases around the world over the last 10 years.
In Angola, the outbreak is growing. It started in the Luanda province on 5 December 2015. Since then it has spread to 16 of the country’s 18 provinces, and 13 of those provinces can link their imported cases to the Luanda province. At this time, there have been at least 1,975 suspected and confirmed cases, including 258 deaths. Transmission is still active so surveillance is a crucial part of the outbreak response. However, the surveillance system is not perfect so the number of cases may be more than what is being reported.
A major immunization campaign has begun in Angola. It started in the Luanda province on 2 February 2016 and continues still. So far the vaccination rates are at least 90% in the targeted areas with almost 7 million people vaccinated. The vaccine being used is coming from the International Coordination Group emergency stockpile. However, there is a global yellow fever vaccine shortage and the emergency stockpile is essentially depleted. The WHO is working with vaccine manufacturers to divert shipments from routine immunization programmes until the emergency stockpile is replenished.
The yellow fever vaccine is still manufactured via an 80-year old low-tech method that takes 6 weeks and utilizes eggs. There are only four manufacturers of yellow fever vaccine, the Pasteur Institute of Dakar, two government-run plants in Russia and Brazil, and Sanofi-Pasteur. These four companies cannot keep up with global demand and the Angola outbreak has really strained the system.
This outbreak is a global threat. Not only is there a vaccine shortage. But there has already been documented cross-border transmission. Cases linked to the Angola outbreak have surfaced in Kenya, Morocco, the Democratic Republic of Congo, and China. And with the global vaccine shortage, an outbreak taking hold in one of these countries would be incredibly difficult for the global health community to contain.