Yellow Fever Crisis Continues to Grow Worse

The outbreak of yellow fever in the west African nation of Angola has already spread to other countries on the continent—and even China—and with vaccine supplies at alarmingly low levels a potential public health emergency of global proportions may be on the horizon.

These are the conclusions of a commentary/review published online on May 6 by the International Journal of Infectious Diseases (IJID). The World Health Organization (WHO) formally declared the outbreak in Angola a level 2 emergency in April of this year.

“Every day that goes by now, people are dying from yellow fever,” the authors of the IJID commentary—John P. Woodall, PhD, and Thomas M. Yuill, PhD, write. “The clock is ticking.”

Dr. Woodall did not respond to requests for comment from Contagion; however, the commentary effectively serves as an addendum to the WHO’s formal statement on the Angola yellow fever outbreak. At the time of the international organization’s initial announcement, there were nearly 2,000 suspected cases of yellow fever in the African country (581 of which had been confirmed) and 238 deaths had been linked to the disease. Since then, those numbers have increased to nearly 3,000 suspected cases and more than 300 deaths.

According to WHO, a vaccination campaign has been underway in the Luanda province of Angola since early February; the region is the home of the nation’s capital and largest city of the same name. However, as Drs. Woodall and Yuill note, the country, one of the poorest on the continent, is “struggling” to complete the necessary vaccination of the population in the area and “more than 10 million more doses are needed to cover the rest of the country completely.”

They add, “The longer the delay in getting them to Angola, the more people will become infected and many will die.”

In addition to reviewing recent outbreaks of yellow fever in Africa and elsewhere, the authors share their views on the potential for success of various approaches designed to curtail the spread of the current one, including two strategies they believe to be ineffective: mosquito control and border control. Although they note that “any action to reduce the numbers of the vector would of course help,” such efforts have yielded only limited effect, given the nature of the mosquito species involved. Yellow fever, like Dengue fever, Chikungunya, and Zika, has been linked with the Aedes aegypti mosquito.

“Mosquito control is not the answer,” they write. “If it worked, Dengue would not be such a problem in the tropics. Because Aedes aegypti is day-biting, bed-nets are only useful for preventing the spread to those who are caring for bedridden patients.”

Similarly, border control efforts have proved largely ineffective, due in large part to the “many uncontrolled border crossings” in the region. There have already been cases of yellow fever reported in Uganda, Kenya, and the Democratic Republic of the Congo, and there have been allegations that border control agents in many of the countries in the region are accepting bribes from unvaccinated travelers in exchange for allowing them entry.

“In the final analysis, the vaccine is the only recourse,” Drs. Woodall and Yuill write. “Studies have shown that the [yellow fever] vaccine is so potent that one-fifth of a dose immunizes just as well—so an existing five-dose vial could protect 25 people. The WHO has the authority to declare temporary use of the lower dose, which would usefully stretch the supply.”

Unfortunately, as the authors note, “vaccination cannot be done without cold boxes and transport for distribution, syringes to apply it, staff to administer it, and aircraft and logistics to deliver it...” They write, “All these were provided by the United Nations agencies to combat the Ebola epidemic [but] the WHO is still suffering from serious, chronic understaffing and underfunding.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.