By Nellie Darling and Dr. Stic Harris
Armed Forces Health Surveillance Branch
One Health is the principle that the health of humans, plants, animals and the environment are interconnected. At this interface is a significant opportunity to prevent and mitigate public health crises. Although not new, this concept has recently risen in relevance.
Changes in climate, globalization and human migration have had an impact on the kinds of interactions between people, animals, and their environment. These changes in interaction can lead to the emergence — or reemergence — of disease. As a single spillover event showed, transmission from bat to human initiated the 2014 Ebola outbreak in West Africa. But One Health principles are applicable across a much broader environment. The Defense Department’s ongoing predictive modeling collaborations and integrated health surveillance efforts reflect these principles as we work to promote, maintain, and enhance health protection of U.S. armed forces.
For example, Rift Valley fever is an acute, febrile and viral infection first identified in livestock within Kenya’s Great Rift Valley in 1910. This infection is commonly reported among animals but also can spread to humans via mosquito bite or exposure to bodily fluids of infected animals. Environmental conditions are also a known risk factor for outbreaks as heavy rainfall and localized flooding enable mosquito breeding to thrive. These factors, unfortunately, translate into outbreaks that disproportionately affect communities vulnerable to economic and environmental changes.
Illustration via Defense Health Agency
However, these same factors also mean public health experts are often able to predict when and where outbreaks may occur to help direct response efforts. NASA, the Department of Agriculture and the Defense Health Agency’s Armed Forces Health Surveillance Branch together developed an outbreak forecasting model for RVF using satellite-derived data based on the observed coupling between RVF activity and El Niño–driven flooding.
In December 2015, the National Oceanic and Atmospheric Administration assessed that the weather pattern episode known as El Niño in 2015–2016 could rank among the top three strongest episodes since 1950. The Department of Agriculture’s RVF Monitor predicted above-normal rainfall leading to an increased risk of RVF outbreaks in northern Kenya, Tanzania, South Sudan, Ethiopia, Chad and Niger and parts of Mali, Nigeria and Saudi Arabia in August 2016. These predictions proved accurate as an outbreak of RVF began that month in Niger and areas bordering Mali. As of Nov. 21, the Centers for Disease Control and Prevention reported 240 human cases of RVF [including 32 deaths], 39 cases in cattle, as well as 363 cases of miscarriage and 370 deaths in small sheep and goats since the start of the outbreak.
The RVF outbreak shows how public health experts apply the principles of One Health to predict, and ideally mitigate, disease outbreaks. There is still room for improvement in outbreak response in geographic areas with limited infrastructure. Once an infected mosquito is identified or an outbreak in animals is reported, preventive actions can be initiated. Such actions include vector control, animal vaccinations, restricting the movement of livestock, and warning against contact with infected animals. Mosquito nets, repellents and insecticide-treated uniforms can be utilized in areas of U.S. military operations. By examining public health problems through the lens of One Health, we can effect change in a more timely fashion and have a broader impact on the health of humans and animals worldwide.
Nellie Darling is a contract epidemiologist for the Alert & Response Operations team of AFHSB’s Integrated Biosurveillance section.
Dr. Stic Harris is an epidemiologist, veterinarian and Chief of the Alert & Response Operations team in AFHSB’s IB Section.
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