Yellow fever: an old disease with new plot twists

“An outbreak of yellow fever in Angola could go global,” announces the subhead of “Yellow Plague,” an ominously titled article in a recent edition of the Economist. Yellow fever—named for the jaundice it causes in its severe form—is difficult to diagnose because it begins with vague symptoms like fever, muscle aches, nausea, and weakness. But it claims the lives of about half of those who enter its toxic phase of compromised kidney and liver function. It has, quite literally, plagued us for several hundred years, but this old disease has a few new plot twists.

The spread of yellow fever across oceanic distances predates plane travel; it crossed the Atlantic on slave ships from Africa to South America. However, as the Economist article notes, yellow fever has never been present in Asia, and the travel of Chinese workers to and from Angola is increasing the risk of introducing the disease into the region for the first time, potentially sparking a chain reaction of disastrous proportions, especially in urban settings. Moreover, the Aedes aegypti mosquito, the vector for yellow fever (as well as chikungunya, dengue, and Zika), is showing up in an increasing number of regions, creating even greater opportunities for disease transmission.

The conditions are ripe for a global outbreak, but PATH and our partners are working to help fortify countries’ strongholds against yellow fever and other emerging threats.

Although there is a highly effective vaccine, there is low demand for it in rich countries where there is currently no yellow fever. As a result, only a few manufacturers produce the world’s supply.

PATH is a global leader in accelerating the development, delivery, and introduction of vaccines that protect children and communities from disease. As an outgrowth of our efforts to strengthen manufacturing practices and improve yellow fever vaccine yields, PATH is working alongside the World Health Organization and other partners with a select group of developing-country vaccine manufacturers (DCVMs). Fortunately, strengthening DCVMs’ knowledge and practice of international Good Manufacturing Practice regulations will pay dividends in securing an adequate vaccine supply for other global health threats, too.

Taking migratory movement patterns into account, we’ve learned that previous vaccination campaigns targeted too narrow a population. How do we know that? Surveillance data. Systems that can better detect and respond to outbreaks.

Knowing that real-time, high-quality information is crucial for swift decisions that prevent or manage outbreaks, PATH’s CDC-funded Global Health Security project is working with countries to improve their responsiveness through more appropriate and effective surveillance, data warehouses and diagnostics. It’s a health systems strengthening approach that will benefit efforts to combat Ebola, Zika, and as yet unforeseen outbreaks.

When diseases innovate, we must innovate, too. Yellow fever may have a few surprises up its sleeve, but we’re up for the challenge.