When, this week World Health Organization Director-General Margaret Chan visited Angola, she called for urgent action to respond to an outbreak of yellow fever there that she called the worst the country has seen in 30 years. It was a reminder that, in the midst of the ongoing impacts of the spread of Ebola and Zika, the concept of responding to predictable health threats before they become emergencies remains far from reality.
Angola’s current yellow fever outbreak, which began in December, has now been reported in 16 of the country’s 18 provinces, with more than 1,100 suspected and confimed cases, and at least 168 deaths. Cases in at least 13 provinces are reported to be linked to the Luanda province where the outbreak began, while others are now reporting cases with no known links to the site. Among the four countries bordering Angola, possible cases have been reported in one, the Democratic Republic of Congo, so far, as well as China and Kenya, countries linked by trade, travel and work. Causing severe illness in about 15 percent of those infected, it kills at least half of those. WHO notes that supportive care can offer a chance to seriously ill patients, but is hard to find in settings where the virus is spreading.
Like Ebola, the virus that causes yellow fever has found room to spread out in fast-growing African cities where inequities, inadequate infrastructure and close quarters feed the spread of infectious diseases and where health resources to support diagnoses and treatment of disease as well as surveillance and monitoring of outbreaks are scarce. Like Zika, as well as dengue and chikungunya viruses, its spread is helped by fertile breeding grounds for the mosquito that carries the disease, supplied by reliable pools of standing water in urban settlements where plumbing is a luxury. But still the latest outbreak as well as the unprecedented speed and scope with which it has spread, remains an event treated as unexpected — and now urgent.
Unlike the other diseases, the virus has been controlled, even in some places conquered by a vaccine. But the stockpile of available vaccine is “completely depleted,” WHO reports, with the 5.7 people vaccinated in an emergency campaign leaving more than a million and a half people at risk in the epicenter of the outbreak alone still unvaccinated.
While lack of steady demand has been cited as the reason for the shortage, the odds of future, faster yellow fever outbreaks increase roughly in sync with the growth of cities in health-resource poor countries, WHO has noted. Growing at nearly twice the average of cities worldwide, their density will offer a promising setting for vectors and the diseases they bring, as well as other infectious illnesses — or for vaccines and other tools with which to build the foundations for health security.