Yellow fever could be on the verge of exploding out of central Africa and spreading to Asia, which has never before suffered a major outbreak. The most likely route of transmission: any one of the thousands of unvaccinated Chinese expatriates who are building roads, dams and other big projects in the region. Health authorities already know of at least a dozen workers who returned to China earlier this year and turned out to be sick with yellow fever. How many more infected workers might escape official notice and quarantine, thereby allowing the mosquito-borne virus to gain a toehold in a new part of the world?

The World Health Organization is rushing to play catch-up, planning to send millions more doses of vaccine, extra supplies and even a mobile lab to test samples in distant parts of the DRC. But there are no guarantees that all the extra equipment, even if it arrives quickly, will halt the spread of yellow fever before October and the traditional start of the rainy season. A reporting trip to the DRC in July revealed just how haphazard the response has been to date. Continue reading.