Yellow fever, polio reports highlight obstacles to disease prevention, control, eradication

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In areas of where staff, supply and training gaps join with population mobility and political instability to compromise surveillance efforts, control of diseases for which preventive vaccines exist remains elusive

A little more than four months after the December 2015 start of an urban outbreak of yellow fever in Angola, the health ministry of the neighboring Democratic Republic of the Congo announced a locally driven outbreak of the vector-borne virus had begun within its borders as well.

Yellow fever is a virus so easily spread that one confirmed case is all that is needed to recognize a local outbreak, but, within a month of the announcement, the country had seen more than 450 suspected cases, with the deaths of 45 people attributed to the disease. Among them, 90 percent were reported in Kongo Province, a place also seeing a higher-than-average rate of fatality from the disease. Within that province, a market city on DRC side of the Angola border that is crossed by as many as 40,000 travelers weekly was home to the highest number of cases.

The city, Lufu, lies on a border so porous and so busy that researchers reporting the yellow fever outbreak say 65 or more people were seen crossing the border every minute over the course of a 10-hour period on a market day. This was one of the challenges facing the four health workers assigned to identify travelers with fever and jaundice, take travel histories and check yellow fever vaccination certificates.Other challenges included lack of sterile and appropriate supplies to collect the samples needed to confirm yellow fever diagnoses, and an average four-day lapse between the collection of blood samples and their arrival at the laboratory where they would be tested. Finally, personnel trained to handle the specimens were in short supply, leading to mishandled specimens. Researchers say that, in turn, led to lower rates of case confirmation than might have been expected; while about 27 percent of suspected cases in Angola were confirmed, 9.4 percent of those in the DRC outbreak were.

The report on the DRC yellow fever outbreak, in last week’s Morbidity and Mortality Weekly Report from the U.S. Centers for Disease Control and Prevention, was followed this week by a report on factors that have stymied polio surveillance efforts that the authors say are essential to eradicating the disease. That surveillance starts with reports of  rapid onset muscle weakness among children 15 years or younger,  includes laboratory testing of stool samples  from afflicted patients, and  also includes sampling of sewage in selected locations. While hailing progress in surveillance measures, including a more than six-fold increase in the numbers of sewage surveillance locations in Afghanistan, Pakistan and Nigeria between the end of 2011 and the present, the authors note that gaps continue. Ongoing conflict limits surveillance efforts in Somalia, South Sudan and Syria.The 2014 Ebola crisis in West Africa compromised surveillance efforts in the most effected countries. In the DRC, Ethiopia, Gabon, Madagascar and Niger, issues with the delivery of specimens to laboratories compromise their quality. All of these need to improve, and be monitored within countries where challenges continue, the authors write.

They note that until the polio viruses are eliminated from every country, “all countries remain at risk.”

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