|Areas With Endemic Yellow Fever - Credit CDC|
While endemic in Africa's tropical rain forests, over the past few months Angola has been in the grips of their first urban Yellow Fever (YF) epidemic in decades (see WHO Angola grapples with worst yellow fever outbreak in 30 years). Unlike the forest, densely populated cities present mosquitoes with a target rich environment which can help sustain an outbreak.
Once a scourge in both Europe and North America (see Not Without Warning - The Return Of Mosquito Disease Threats) Yellow Fever is only endemic in parts of Africa and South America (see map above) today.
But, with our increasingly global society, exported YF cases have already turned up in China, Kenya, Mauritania, and the DRC, and further international spread is considered possible.
Earlier this week the medical journal JAMA published Yellow Fever - A New Global Health Emergency? that called for an IHR Emergency Committee Meeting while on on Wednesday we saw ECDC announce they are sending a Medical Mission To Angola To Review Yellow Fever Outbreak.
Six weeks ago the ECDC issued a rapid risk assessment on this outbreak (see Yellow Fever In Angola & The Risk Of International Spread - ECDC), which warned:
As yellow fever and dengue fever share the same mosquito vector, Aedes aegypti, any area where dengue has been transmitted could be suitable for establishment of local transmission of yellow fever if the virus is introduced by a viraemic traveller.
All of which brings us to a new Epidemiological Update from the ECDC on the ongoing outbreak in Angola.
Epidemiological update: Outbreak of yellow fever in Angola
12 May 2016
An outbreak of yellow fever that started in December 2015 in the municipality of Viana, Luanda province, has been spreading to other provinces of Angola in the past weeks. A rapid increase in the number of suspected cases was recorded since mid-January 2016. As of 8 May 2016, the Angolan Ministry of Health has reported 2 267 cases and 293 deaths. Of those, 696 cases are confirmed. Of the confirmed cases, 445 are from Luanda and 251 are from outside of Luanda. Confirmed cases have been reported in 14 of Angola 18 provinces. This week, Namibe province (south of Angola, bordering Namibia) was reported as affected.
Yellow fever cases in people who travelled from Angola have been reported in China (11 cases), Democratic Republic of the Congo (37 confirmed cases), Kenya (two cases), Mauritania (one case) and Namibia (one case).
More than seven million people in Luanda have been vaccinated through a large-scale vaccination campaign since the beginning of February, using vaccines mobilised through the yellow fever vaccine emergency stockpile made available through the International Coordinating Group for Vaccine Provision, with support from Gavi, the UN Central Emergency Response Fund, and a vaccine donation from Brazil.
On 5 May 2016, the Ministry of Health of the Democratic Republic of the Congo (DRC) issued an update on the yellow fever outbreak. Since the beginning of January 2016 and as of 4 May 2016, DRC has reported five probable cases and 39 laboratory-confirmed cases: 37 imported from Angola, reported in Kongo central province and Kinshasa, and two autochthonous cases in Ndjili, Kinshasa and Matadi, Kongo Central province. The possibility of locally acquired infections is under investigation for at least 10 non-classified cases in Kinshasa and Kongo Central provinces.
A response plan, involving the Ministry of Health, WHO and non-governmental organisations has been developed. It includes a vaccination campaign in eight health zones, the six districts of Kongo Central and at least two districts in Kinshasa.
On 29 April 2016, media quoting the Ministry of Health in Namibia reported one confirmed case of yellow fever. In addition, media sources last week reported a suspected case of yellow fever at the Engela district hospital in the Ohangwena region. The patient had travelled to Lubango in Angola and was transferred to the Oshakati Hospital and later discharged.
In Uganda, on 5 May 2016, WHO issued an update on the yellow fever outbreak in Uganda, which is unrelated to the outbreak in Angola. Between 26 March and 18 April 2016, health authorities reported 41 yellow fever cases, including seven deaths. Among them, seven cases and two deaths were laboratory-confirmed. The 41 cases are reported in the districts of Masaka, Rukungiri, Ntungamo, Bukumansimbi, Kalungu, Lyantonde, and Rakai. None of the cases had a recent travel history to Angola.
WHO estimates that 508 million people are living in 31 African countries at risk for transmission of yellow fever. Therefore, the large outbreak of yellow fever in Angola is of concern with regard to the risk of introduction of the virus through viraemic travellers to countries at risk of transmission, especially in neighbouring countries. In DRC, the confirmation of the autochthonous circulation in the capital is a major concern as Kinshasa is highly populated, representing a risk of extension to Brazzaville, the capital of the Republic of the Congo, that is located across the Congo river.
ECDC published a rapid risk assessment on 25 March 2016. The Aedes aegypti mosquito, a competent vector for yellow fever, is not present in continental Europe but is present in the island of Madeira, an autonomous region of Portugal where the weather conditions are not currently suitable for high mosquito activity.
Proof of vaccination is required for all travellers aged 1 year and above entering Angola and DRC. WHO recommends vaccination for all travellers older than 9 months of age in areas where there is evidence of persistent or periodic yellow fever virus transmission. European citizens travelling to, or residing in, Angola should be vaccinated against yellow fever as per their national health authorities’ recommendations. Vaccine should be administered at least 10 days before travelling.
Yellow fever in an urban setting is considered a public health emergency that may result in a large number of cases. Vaccination is the single most important and effective measure for preventing yellow fever. Therefore, additional cases in unvaccinated populations related to this urban outbreak should be expected, until a sufficient proportion of the susceptible population is immunised. The outbreak in Angola, DRC and Uganda is not yet controlled and is currently expanding to additional provinces challenging the ongoing mass vaccination campaign with a potential vaccine shortage in the coming months. The control of the outbreak in the three countries is needed in order to prevent further spread in the region and beyond.