Out of sight, out of mind. That’s the painful lesson yellow fever has taught us.
Story by: Devy Elling
In December 2015, a case of yellow fever in Luanda, Angola was detected. This was the first case that birthed a full blown outbreak in Angola and its neighbouring countries. Distant countries like China have also reported cases of yellow fever linked to Angola, making this the most serious outbreak since the 1930s.
The first written record of yellow fever was in Barbados in 1647 and the virus had gone on to plague humanity for almost three centuries.
Yellow fever was (and still is) particularly virulent in West Africa and South America. However, this does not mean that other regions are immune. One of the most infamous incidents linked to yellow fever was the Philadelphia (then the capital of the United States) plague of 1783 which wiped out 10 percent of the whole population.
A virus of such proportions demanded steps to eradicated it. Money and research was poured into studying the disease and in the 1930s a powerful vaccine was developed and occurrence had decreased tremendously.
By the turn of the millennium, the last frontier of the disease was West Africa. Since the Yellow Fever Initiative was launched by the World Health Organisation (WHO) in 2006 no major outbreaks had been detected in West Africa. The world seemed safe from the once fatal infection.
The disease became a footnote in textbooks.
Yet, the epidemiological yellow fever almost poetically jumped from the textbook to reality.
The first reported case in Angola in December 2015 proved not to be an isolated incident but the first drop in a flood of infections. The number of suspected cases in Angola continued to rise in the beginning of 2016. Because the brunt of the disease was in West Africa, vaccination campaigns against yellow fever were not prioritised in Eastern, Southern and Central Africa (Angola is a southern African nation) and any in these populations remained vulnerable to the virus.
The Angolan Ministry of Health ordered 5 million vaccine doses to vaccinate her citizens in Luanda from further spread. However, the order size was not enough to allow for a mass vaccination of the whole Angolan population (21 million) to prevent further transmission. Barely a month later Democratic Republic Congo and China reported cases in connection. Uganda and Ethiopia followed closely with reports of related infections. The Chinese case was particularly worrying as Asia has not had a history of yellow fever outbreaks. The outbreak reporting system ProMED mail warned that Asia’s luck might run out, as vaccine stockpiles in the continent were insufficient. Should the infection spread in Asia, there would be almost no Asian country prepared to deal with the fall out.
In April this year, Margaret Chan, Director General of the World Health Organisation (WHO) stated, “[the yellow fever epidemic was] the most serious outbreak of yellow fever that Angola has faced in 30 years”. The European Disease for Control and Prevention (ECDC) reported an increase in the number of cases and mortality.
While national governments seemed to have dropped the ball, the WHO was much more prepared. In fact, the WHO responded to yellow fever outbreaks quicker than to Zika or Ebola. Only a few weeks after the first case was detected, they collaborated with international groups to start mass vaccination campaigns in Angola. Besides the mass vaccination campaigns, mosquito control and surveillance were conducted in different parts of the country. The crisis seems to have eased, all in 4000 Angolans, 2400 Congolese and 90 Ugandans have been detected in this time. The death toll stands at 400. Fortunately, no new cases have been identified, suggesting a decrease of disease transmission.
By the time Science interviewed them, the WHO was in the position to clarify that the outbreak was not an emergency because the international spread had decelerated and vaccine supplies were recovering.
The outbreak broke because of our human ability to forget history. It may have happened in Africa today, but it does not mean a similar outbreak cannot reappear closer to home. Two years ago, we heard devastating counts of lives lost due to Ebola. Last year, we heard about Zika, and earlier this year, it was yellow fever. And yet the yellow fever story is different. This is not an unexpected, unplanned disease. The spread happened because yellow fever was not properly prevented.
The steps required to prevent yellow fever are fairly direct – vaccination and contact avoidance with mosquitoes in high-risk areas. However, due to inadequate vaccination campaigns, at-risk populations had not been immunised in many parts of the world.
How can we improve our healthcare systems in order to prevent a disastrous outbreak of previously treated diseases in the future?
Vaccine could be integrated into each country’s health policy. This would have the effect of lowering the risk of contracting a disease. On a logistical front, compulsory vaccination would have the best reach of all potential at risk individuals. Yet, there is a cultural component to every country or region. A compulsory vaccination may reach a huge chunk of the population, but it can also have an adverse effect when the population feels as though they are forced to get something injected in their body without fully understanding what it is. Small populations in backward regions have been known to reject vaccine treatment. There is also a growing anti-vaccination trend particularly in some developed countries. The best solution to this is by spending on public health education for the general public.
While the practical steps are straightforward, the decision making process is more complicated. First, inadequate vaccination campaigns may be overshadowed by other competing priorities. The recent successful history against yellow fever would further drive down the priority of yellow fever vaccination. A lack of commercial demand would lead to a fall in production, which would result in rising cost per drug and longer lead times for production.
Second, in places where yellow fever is not prevalent, how does the government fund a vaccine that is desperately needed? Few governments are in a position to subsidise vaccination of a potentially unimportant disease.
Third, controls on foreign travellers to and from the country. Visitors might not always have against different diseases in foreign country. With increasing travel within and between nations, transmission risk follows the same pattern. Can countries with high transmission risk enforce some control about visitors’ health coverage without hurting tourist numbers?
This year, we have seen how an outbreak created chaos in the health sector. We sometimes forget that diseases, such as yellow fever, existed. Our complacence would be our failure. As the yellow fever outbreak has shown, diseases that have previously occurred can happen again.
Healthcare policy and lessons must be learnt from this near scare – we must continually watch that the footnotes do not again become headlines. A sustainable solution is more complex we think, yet a solution needs to be derived because complacency is a dangerous option.