Yellow Fever - Africa: Angola comment

The World Health Organization (WHO) called for strengthening the quality of the response against the epidemic of yellow fever in Angola today [19 Apr 2016], according to a statement of the specialized agency released by the media. There is "an urgent need to strengthen the quality of response in Angola, as well as to increase the immunization control of travellers coming from the regions affected by the disease," WHO indicates.

It considers that the condition may be a threat to the world, and the greatest risk lies with countries where there is proliferation of _Aedes aegypti_, the [mosquito] transmitter of the disease.

Similarly, it is added, regions with outbreaks of dengue, Zika and chikungunya are fertile grounds for the disease [because of the presence of the common vector of all 4 viruses]. It was known that passengers who left Luanda exported the virus to China, Kenya and the Democratic Republic of Congo, where at least 21 people died because of yellow fever.

According to WHO, 16 out of the 18 Angolan provinces are affected by the disease, discovered in this capital 5 months ago, and the evolution of the situation "causes concern, and it should be monitored". The latest weekly bulletin of the National Health Service reveals that the yellow fever outbreak has caused 242 deaths so far in this African country, out of a total of 1751 cases. From 4-10 Apr [2016], 119 new suspected cases were reported, one of which was confirmed, and 7 died.

From the start of the campaign on 2 Feb [2016] in Luanda, 5.8 million people out of a total of 6.5 million have been immunized. Outside the capital, 10.1 million people have received the vaccine. In the provinces of Benguela and Huambo, the campaign is scheduled to begin with more than a million doses available for each region. Huambo has reported a total of 281 suspected cases, with 40 deaths, and Benguela 51, with no record of human losses.

Yellow fever is a viral disease transmitted by infected mosquitoes and causes fever, muscle aches, loss of appetite, vomiting and nausea, [and jaundice] and can lead to death.

Huambo and Benguela

As Angola grapples with its worst yellow fever outbreak in decades, the Ministry of Health, with the support of WHO and partners have extended the vaccination campaign beyond the capital Luanda into Huambo and Benguela, 2 of the other 5 provinces reporting local transmission. [Cases infected in Luanda have been reported in 16/18 of Angola`s provinces, but local transmission apparently in just 5 of them so far.

Since the outbreak began in December 2015, 1908 suspected cases of yellow fever have been reported (617 laboratory confirmed), and 250 deaths have been reported. The majority of the cases are concentrated in Luanda and in 2 other provinces, namely, Huambo and Huila. It is not clear why the extension of vaccination has been to Benguela when Huila has more cases.

In order to contain the outbreak outside the capital, nearly 2.15 million people will be vaccinated in 5 densely populated urban districts in Huambo and Benguela provinces over the coming weeks. [It is not clear why it isn`t possible to organize vaccination for more than an average of about a half million people a week, when there is no resistance to vaccination [6 million were vaccinated in 11 weeks in Luanda Mod.JW] Around one million people in the 2 provinces have been vaccinated thus far. "This targeted vaccination is critical to protect those most at risk countrywide and to stop the further spread of infection by making the best use of available global vaccine supplies," said Dr Matshidiso Moeti, WHO regional director for Africa.

Since 2 Feb 2016, [11 weeks ago] close to 6 million people in Luanda have benefited from a large scale vaccination campaign using vaccines made available from the yellow fever vaccine emergency stockpile made available through the International Coordinating Group (ICG) for Vaccine Provision, with support from Gavi (the Vaccine Alliance); the UN Central Emergency Response Fund (CERF), and a vaccine donation from Brazil.

Along with the vaccination campaign, the Ministry of Health, WHO and partners are working to strengthen disease surveillance and diagnostic capacity, both within Angola and neighbouring countries, and to enhance vector control, including using community-led public health education campaigns. "The immediate concern is that the virus might spread to other urban centres in Angola and other countries. WHO urges all countries, especially those that border Angola, to increase disease surveillance and strengthen vector control as well as to ensure that all those travelling to Angola are vaccinated," says Dr Bruce Aylward, executive director, Outbreaks and Health Emergencies, WHO.

Angola's outbreak has stretched existing yellow fever vaccine supplies. During outbreaks, available vaccines are prioritized for the emergency response. At the end of March 2016, thanks to ICG partners, including UNICEF, the yellow fever emergency vaccine stockpile was replenished, and approximately 10 million doses of the vaccine are now available.

Concerns exist that if yellow fever should spread to other countries in Africa and Asia, there would be a need to further prioritize vaccine supplies, which would interrupt routine immunization programmes in some countries. "Stockpiling yellow fever vaccine has proved critical in combating the current resurgence of the disease," said Dr Seth Berkley, CEO of Gavi, the Vaccine Alliance. "With 12 million doses of vaccine, including 3 million for Angola, Gavi is the single biggest contributor to the emergency yellow fever stockpile.

The current situation is a reminder of the importance of investing in strong and sustainable routine immunisation programmes to prevent such outbreaks and protect populations' health."

Yellow fever cases in people who travelled from Angola have been reported in 3 countries: China (11 cases), Democratic Republic of Congo (10 cases with 1 in Kinshasa), and Kenya (2 cases). Three yellow fever cases have been reported in the south of Uganda. The patients had no travel history to Angola.

WHO is working with neighbouring countries such as the Democratic Republic of Congo (DRC), Namibia and Zambia to bolster cross-border surveillance with Angola and information sharing to prevent and reduce the spread of infection.

Vaccination is the single most important measure for preventing yellow fever. The vaccine is safe and highly effective, and a single dose provides lifelong immunity [officially 10 years.Mod.SH]. The Government of Angola requires all travellers older than 9 months of age to show proof of yellow fever vaccination upon arrival. People who are travelling to Angola must ensure that they get vaccinated against yellow fever at least 10 days before travel. WHO advises travellers going to and from Angola and other countries where yellow fever occurs to get vaccinated and carry their certificate of vaccination when travelling.

The yellow fever virus is transmitted by infected mosquitoes, the commonest being the _Aedes_ species, the same mosquito that spreads the Zika, chikungunya, and dengue viruses. Mosquitoes become infected with the virus when they bite an infected human or monkey. The disease cannot be spread by contact from one person to another. Yellow fever is endemic in over 43 countries in Africa and South America, with about 900 million people at risk.

Symptoms include fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue. A small percentage of infected people experience a second, more severe phase of illness, which includes high fever, jaundice and internal bleeding. At least half of severely affected patients who don't receive treatment die within 10 to 14 days.

Communicated by: WHO Angola Country Office-Pro Med mail

It is easy to be critical of the 2-month delay in mounting the yellow fever (YF) campaign in the 2 outlying provinces. Dealing with the larger, immediate challenge of YF cases in the Luanda area alone has been and continues to be a formidable logistical challenge and has been given priority for vaccine and personnel. This situation provides a compelling case for the need for national contingency planning prior to the occurrence of an outbreak of YF or other pathogens. YF poses the problem of its capacity for rapid spread in situations where there are populations of abundant vectors and susceptible (unvaccinated) individuals. Rapid, well-planned response is critical when the YF clock is ticking.