Angolan Yellow Fever outbreak threatens African health

A yellow fever outbreak began in Angola in December. By April 2016, Angola had 2023 suspected yellow fever cases, and 258 deaths from infections.

Yellow fever is transmitted to humans by mosquitoes, primarily Aedes or Haemagogus species. On 2 May 2016, the Democratic Republic of Congo (DRC) announced plans to control mosquitoes, and to vaccinate two million people.

This campaign, along with Angola’s measures, could exhaust global vaccine supplies. Chicken eggs are used to produce the vaccine. More than seven million Angolans have been vaccinated.

Yellow Fever symptoms

There are no specific antiviral drugs or immune therapies for yellow fever. Without vaccination, most patients recover from the acute febrile phase with attendant myalgia, headache, back pain, anorexia, nausea, and vomiting within a week, but about one in seven patients develop a second phase that includes high fever, jaundice, bleeding, and kidney damage.

Mortality is about 50% in the patients who develop that second phase of yellow fever.

Yellow fever endemic areas in yellow, and risk areas in dark green.
Yellow fever endemic areas in yellow, and risk areas in dark green.

The outbreak was reported to the WHO on January 21, 2016. The yellow fever outbreak threatens parts of Africa, and Chinese nationals working there.

It also threatens Latin America and Asia, where progammes could exhaust vaccine supplies and trigger a global health emergency.

The World Health Organization (WHO) may convene an emergency committee to mobilise funds, coordinate international response, and spearhead a surge in vaccine production, reported Janis C Kelly in Medscape Medical News

Specialists urged the WHO to adopt a new structure for dealing with fast-emerging international health threats such as Ebola virus, Zika virus (an ongoing epidemic), and yellow fever (JAMA, 9 May 2016; Daniel Lucey, and Lawrence O Gostin, O’Neill Institute for National and Global Health Law, Georgetown University, Washington DC).

The committee would advise the WHO on whether to declare an emergency, and on necessary steps to avert a crisis.

The laboratory-confirmed outbreak of yellow fever involved travellers to Angola in China, the Democratic Republic of Congo, and Kenya. Nambia and Zambia is also at risk.

Vaccine dose could be reduced, and repeated

The authors suggest that WHO use the Emergency Use Assessment and Listing procedures introduced to deal with Ebola to safeguard the yellow fever vaccine supply, by cutting doses in Angola to one fifth of the normal vaccine dose.

They acknowledge that the duration of immunity with such doses is uncertain, especially in children. The proposed measure raises the prospect that vaccinations may have to be repeated.

To authorise a reduced dose, the WHO director-general would have to declare that yellow fever constitutes a public health emergency of international concern or determine such action is “in the best interest of public health,” according to the authors.

The WHO director-general can declare a public health emergency only by convening an emergency committee.

A typical workplace spraying programme to control health risk vectors such as mosquitoes and flies.
A typical workplace spraying programme to control health risk vectors such as mosquitoes and flies.

Prof Peter Hotez of the National School of Tropical Medicine told Medscape Medical News that the recommendation to consider using lower doses of yellow fever vaccine is supported both by reduced-dose studies in individuals with egg allergy, and by a randomised controlled non-inferiority trial showing protective immunity in volunteers given intradermal yellow fever vaccine at one fifth the usual dose.

Affected areas should also coordinate mosquito control.

Source: Medscape Medical News. WHO.

Leave a Reply