Yellow Fever – Angola
On 21 March, the Ministry of Health of Angola provided WHO with an update on the ongoing outbreak of yellow fever (YF), which started on 5 December 2015 in the Viana municipality, Luanda province.
As of 21 March, 16 of the country’s 18 provinces have reported YF suspected cases – 13 of these provinces have reported imported cases linked to Luanda. Local transmission of the disease was documented in 2 of the 11 municipalities of Huambo province. Other provinces have reported autochthonous suspected cases with no epidemiological links to Luanda. These cases are being investigated and outcomes of these investigations will be known in the following days.
To date, at least 1,132 suspected and confirmed cases have been reported nationally, including 168 deaths. A total of 375 cases have been laboratory-confirmed. Luanda, the outbreak epicentre, remains the main affected province with 818 cases (281 confirmed confirmed), including 129 deaths. However, the number of cases reported in provinces other than Luanda is apparently increasing.
Public health response
A national task force was activated and is now leading the response to the outbreak. WHO is providing support for the coordination of the response operations. On 12 February, WHO declared this outbreak a “grade 2 emergency”, in accordance with the Emergency Response Framework (ERF). Since then, 65 WHO multidisciplinary experts have been deployed to provide high-level technical support to the country.
The Immunization campaign in Luanda, which started on 2 February in Viana, is still ongoing and has so far been implemented in 6 municipalities out of the targeted 12. Three municipalities are reporting high coverage rates (≥90%) while other municipalities are reporting even higher rates (136% in Viana and 113% in Bela) probably due to people coming from other districts of Luanda as well as other provinces.
Surveillance and investigations of newly affected areas are ongoing as well as social mobilization activities. So far, vector control activities are mainly oriented to the control of the mosquito breeding sites.
WHO risk assessment
The evolution of the situation in Angola is concerning and needs to be closely monitored in the whole African region. Partly, the reported drastic increase in the number of confirmed cases could be attributed to backlog testing. However, the dates of symptom onset of the recently-confirmed cases indicate that transmission is still active in Luanda – mainly in unimmunized districts and probably in other provinces. Surveillance is reportedly not optimal, especially in the border areas, and a higher number of suspected cases cannot be excluded.
Of particular concern is the cross border and international spread risk of the disease, which has already been documented, with cases recently rumoured to have been exported to China, Kenya and the Democratic Republic of Congo. WHO continues to monitor the epidemiological situation and conduct risk assessments based on the latest available information. It is important to know that imported cases do not represent an outbreak. Although the threat of an outbreak exists, this is considered to be low when the risk factors (susceptible vectors and susceptible human populations) are not present.
WHO urges Members States, especially those where the establishment of a local cycle of transmission is possible (i.e. where the competent vector, the Aedes aegypti mosquito, is present), to strengthen the control of immunisation status of travellers to all potentially endemic epidemic areas.
In the context of an active Yellow fever outbreak in Angola, special attention should also be placed on travellers returning from Angola and other potential epidemic areas. Travellers, particularly those arriving to Asia from Africa or Latin America must have a certificate of yellow fever vaccination. If there are medical grounds for not getting vaccinated, International Health Regulations state that this must be certified by the appropriate authorities.
WHO does not recommend any restriction of travel and trade to Angola on the basis of the information available on this outbreak. The vaccination of each person before going to the affected areas as well as measures to avoid mosquito bites are sufficient for the prevention of the disease.