Six weeks ago, in WHO : Yellow Fever Outbreak In Angola we looked at a report that cited 164 suspected cases and 37 deaths over roughly 2 months. Yellow fever is a mosquito-vectored flavivirus, similar to, but deadlier than Dengue and Zika virus.
Today the WHO is back with an update that cites at least 1,132 suspected and confirmed cases, including 168 deaths.
Once a scourge in both Europe and North America (see Not Without Warning - The Return Of Mosquito Disease Threats) yellow fever today is only endemic in parts of Africa and South America. There are concerns, however, that like Zika, CHKV and Dengue, it could one day expand its range.
- 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.
- And in 2013 Peter Hotez - Dean of the National School of Tropical Medicine at Baylor College of Medicine - and Kristy Murray, an associate professor of pediatrics at Baylor College of Medicine who studys mosquito-borne diseases, penned a PLoS Blog entitled. Could Yellow Fever Return to the United States?
Spolier alert, it could.
This from the World Health Organization.
Yellow Fever – AngolaOn 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 assessmentThe 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.