We've been following the Yellow Fever (YF) outbreak in Angola - that nation's largest in 30 years - since early February. An epidemic that now threatens to spill over into neighboring countries (see WHO Yellow Fever Update - DRC), and that could even be carried well beyond the African continent (see Yellow Fever In Angola & The Risk Of International Spread - ECDC).
While Yellow Fever has been successfully eradicated from North America and Europe for decades, the mosquito vectors that transmit the virus are still present in some regions.
A 2010 Eurosurveillance Journal devoted an entire issue to The Threat Of Vector Borne Diseases, including making the case for the reintroduction of Yellow fever and dengue: a threat to Europe? by P Reiter.
While in 2013, Peter Hotez - Dean of the National School of Tropical Medicine at Baylor College of Medicine - along with Kristy Murray, an associate professor of pediatrics at Baylor, posed a similar question in Could Yellow Fever Return to the United States?
In both cases, the answer is `yes'. It's possible.
Any place susceptible to Dengue, Chikungunya, or Zika is potentially at risk of seeing local transmission of Yellow Fever from imported cases. Today, the World Health Organization posted the following update, with a risk assessment on the possible spread of the epidemic beyond Angola.
On 21 January 2016, the National IHR Focal Point of Angola notified WHO of an outbreak of yellow fever (YF). The first case with onset date on 5 December 2015 was identified in Viana municipality, Luanda province.
As of 7 April 2016, a total of 1,708 suspected cases, including 238 deaths (CFR: 13.9%), had been reported from 16 of the country’s 18 provinces. Luanda remains the most affected province with 1,135 cases (405 confirmed), including 165 deaths (CFR: 14. 5%). The other most affected provinces are Huambo (266 suspected cases, 37 deaths), Huila (95 suspected cases, 16 deaths) and Benguela (51 suspected cases, 0 deaths). Between 6 and 7 April, 30 new suspected cases, including 4 deaths, were reported across the country – 19 of these suspected cases and 2 of the reported deaths came from Luanda.
A total of 581 cases have been laboratory confirmed in 59 districts of 12 provinces. Luanda province, the epicentre of the outbreak, accounts for 70% of the confirmed cases (405 cases). Other provinces with a high number of confirmed cases include Huambo (73 cases), Huila (27 cases), Benguela (22 cases) and Kuanza Sul (11 cases). From 6 to 7 April, 30 new confirmed cases were reported from Luanda (19), Huambo (4), Cuanza Sul (2), Cunene (2), Bengo (1), Lunda Norte (1) and Uige (1). The number of laboratory confirmed cases in provinces other than Luanda continues to increase. The risk of spread to other provinces and to neighbouring countries remains very high.
Transmission of the disease is no longer restricted to Luanda. As of 7 April 2016, the National Final Classification Committee had confirmed local transmission in five other provinces (Benguela, Cuanza Sul, Huambo, Huila and Uige) and in a total of 10 districts.
In addition, international spread of the disease has already been documented. Recent imported cases of YF have in fact been detected in China, Kenya and the Democratic Republic of the Congo (DRC) (see DONs published on 11 and 6 April).
WHO risk assessment
The evolution of the situation in Angola is concerning and needs to be closely monitored. The reports of imported cases of YF in China, DRC and Kenya demonstrate that this outbreak constitutes a potential threat for the entire world.
There is a risk for the further spread of the disease in view of the large international communities residing in Angola and the frequent travel activities with neighbouring and overseas countries. Furthermore, all countries where the mosquito vector (Aedes species) is present are at risk, notably those endemic for or previously affected by outbreaks of Dengue, Chikungunya or Zika virus and other arboviruses.
Therefore, there is an urgent need to strengthen the quality of the response in Angola and to enhance preparedness activities in neighbouring countries and in countries that have diaspora communities in Angola. WHO continues to monitor the epidemiological situation and conduct risk assessment based on the latest available information.