Lab Matters Winter 2020 | Page 22

INFECTIOUS DISEASES CDC’s Yellow Fever Diagnostic Kit Could Mean Faster Outbreak Response, Fewer Deaths By Maggie Silver, MPH, Arboviral Diseases Branch, US Centers for Disease Control and Prevention Yellow fever is one of the oldest- recognized mosquito-borne diseases in the world. Those who become infected with the virus are at risk for severe liver disease with bleeding and yellowing skin. Between 30 to 60% of those who develop this severe form of the disease will die. Despite having an effective vaccine since the 1930s, we continue to see outbreaks occur, particularly in Africa and South America. In 2016-17, nearly 1,000 cases of yellow fever were confirmed in Angola and Democratic Republic of Congo, and around 2,700 cases have been confirmed in Brazil since 2017. These totals are likely much higher since many people didn’t seek treatment or died before their diagnosis could be confirmed. Being able to quickly identify yellow fever infections is crucial to stopping an outbreak. When a yellow fever outbreak occurs, public health officials must mobilize quickly, as the disease can spread rapidly within a region. Fast, accurate identification of yellow fever cases allows health authorities to swiftly implement mass vaccination campaigns that can prevent further illness. This is why the global strategy to Eliminate Yellow Fever Epidemics (EYE), enacted by the World Health Organization (WHO) in 2016, includes improved diagnostic testing and early detection as part of its strategy. Currently, no validated commercially available yellow fever tests exist. For the last five years, researchers at the US Centers for Disease Control and Prevention (CDC) have been looking for ways to transform the current, highly specialized test (IgM-capture ELISA) into a test accessible to laboratory staff working in resource-poor countries. All those years spent in the lab trying to streamline the traditionally complex process have begun to pay off. The CDC yellow fever diagnostic research team, led by Jane Basile and Christin Goodman, have managed to produce a yellow fever diagnostic kit that cuts previous processing time from three days to just four hours. The kit is 20 LAB MATTERS Winter 2020 CDC Researcher Jane Basile (center) works with attendees at the yellow fever workshop in Cameroon. Photo: CDC CDC validated the new YF MAC-HD test kits during the 2016 Angola outbreak and found that the method was easily transferable, and that the kit was sensitive and specific. Now, with support from the Association of Public Health Laboratories, CDC, WHO and Gavi, Basile and Goodman are taking their kits on the road and teaching other laboratorians how to use them. aptly named the “yellow fever M-antibody capture-half day” (YF MAC-HD). Diagnosing yellow fever can be difficult due in part to the way symptoms occur, as well as the lengthy, technically demanding diagnostic test. Not only does the current front-line yellow fever diagnostic test take three days to complete, but it requires highly trained laboratory staff who must order and calibrate multiple test components (reagents) in order to accurately perform a test. Since most yellow fever outbreaks occur in resource- poor countries, where electricity, water and even reliable shipping can be an issue, this new diagnostic kit is a valuable tool in combatting yellow fever outbreaks. To address the technical challenges of performing the existing serologic test, Basile and Goodman created pre-measured, calibrated test components to allow the YF MAC-HD to be performed easily in resource-limited settings. This required a great deal of work producing materials and testing complex matrices of components before arriving at the best combinations. The most critical of the kit components are freeze dried to improve stability, and the end-user simply adds water. Each kit can test up to 24 samples and is relatively shelf-stable—although refrigeration is recommended. PublicHealthLabs @APHL