The news pages continue to be filled with stories of public health systems overwhelmed by the introduction of Zika virus across the Western Hemisphere. While experts debate the role of institutions, clinicians and mosquito-control professionals in managing this new health threat, the reality is that there is nothing new about how local communities can adapt and respond.
The Americas have battled the mosquito Aedes aegypti for over a hundred years, originally in the fight against yellow fever, and more recently in suppressing dengue fever, chikungunya fever, and Zika, all transmitted by this same pest.
Fifty years ago, efforts to eradicate Ae. aegypti from the Americas ranked among the 20th century’s greatest global health success stories. But then it became one of our biggest failures. Institutionalized vector control programs had pushed Ae. aegypti to the brink of elimination, but global health resources were gradually redeployed to more pressing needs (particularly the emergence of HIV in the 1980s), and this urban mosquito resurged with a vengeance in our ever-urbanizing world.
How are communities responding to Zika in 2016? The same rules apply: public education about protection from mosquito bites, vector control, clinical case management and international agency oversight. Why does this sound easier said than done? Historically we have not excelled at all of these activities simultaneously because there has rarely been so much at stake.
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The majority of people exposed to dengue, chikungunya and Zika show no symptoms, and the vast majority with symptoms are mild cases. Dengue, in particular — which has shaped urban vector control efforts in the Americas over the past few decades — has a very low fatality rate and normally resolves in seven to 10 days without long-term health effects. Chikungunya leaves a small number of patients with longer-term arthritic symptoms, though often quietly, appearing weeks or months after the initial infection.
But Zika’s legacy of microcephaly, Guillain-Barré, and other neurological symptoms — which produce lifelong disabilities, decreased life expectancy, and longer-term burdens on health care systems — is more visible and heart-wrenching than that of dengue and chikungunya.
Suddenly there is a lot at stake.
Across the Atlantic, Bill Gates and British Chancellor George Osborne recently pledged £3 billion ($4.3 billion) over the next five years to eradicate malaria, another mosquito-borne disease. The scientific malaria literature — much of it funded by the Bill & Melinda Gates Foundation — has been increasingly peppered with high-profile, back-slapping articles celebrating the success of control efforts in suppressing the disease. Few other disease distributions have been so thoroughly mapped, analyzed and simulated.
Gates believes that malaria eradication is achievable, and he’s probably right. But what is missing is an acknowledgment that the global drop in malaria cases has also been fueled by rapid urbanization — which limits breeding of the more rural Anopheles mosquito that transmits malaria — and improved diagnostics that help us distinguish malarial fevers from other infections. In fact, cutting-edge research tells us that in many tropical urban areas where malaria diagnoses predominate, malaria is no longer our biggest problem.
These recent developments concerning Zika, malaria, and especially last year’s unprecedented Ebola outbreak, humble us and demonstrate how little we still know about infectious-disease ecology. We are awakening to a world where a pathogen previously confined to an African forest can reach a global city in weeks or days. Global health practice has evolved from moral imperative to practical necessity.
Despite substantial inertia, we are slowly breaking out of traditional medical paradigms and getting back to the basics by implementing integrated vector management and deploying better technology to improve diagnoses of fevers. We are probably closer to understanding Zika and eradicating malaria than we realize, but something else will likely emerge to take their place. Perhaps Bill Gates would achieve his vision of malaria eradication faster if resources were more broadly focused on diagnostics and patient management, rather than a single disease.
The global coverage of these issues galvanizes the global health community and inches us closer to innovative solutions such as vaccines, new insecticides, and genetically modified mosquitoes, after which we can move on to the next global health challenge. There’s hope, but we must commit to global health solutions together and put our money where our mouth — and science — is.
Justin Stoler is an assistant professor in the University of Miami’s Department of Geography and Regional Studies, Department of Public Health Sciences.