The race for a Zika vaccine, one of the most pressing priorities in global health, is at full throttle. More than a dozen companies and government institutions are working to unlock the secrets of the virus, and a vaccine could be available as early as 2018.
But available to whom? If history is any guide, impoverished communities in Africa are likely to be the last in line. And this despite a mounting body of evidence that, contrary to the prevailing wisdom, poor families in Africa might bear the greatest burden of the disease.
Indeed, much of what we have taken for granted about Zika — that it is a threat unique to the Western Hemisphere; that it may only recently have evolved the ability to cause microcephaly and brain damage in babies; and that it hasn’t hurt women and children in Africa — is now in serious doubt.
We know that Zika was first identified in Uganda, in 1947, and that the first documented urban outbreak of the virus occurred in Libreville, the capital of Gabon, in 2007. We know that African strains of Zika — which can probably be transmitted sexually and from mother to child — are present in at least 25 countries across the continent. And we know that Guinea-Bissau, the only mainland African nation to send Zika testing results to the World Health Organization in 2016, has reported three microcephalic babies with clinical data suggesting Zika exposure.
Most worrisome, though, is what we’ve learned from laboratory investigations over the past year. So far, at least 16 studies published in scientific journals have demonstrated that African strains of Zika can cause the same kinds of cellular damage we’ve seen in the Americas. According to one study by French virologists, a strain of Zika isolated in the Central African Republic was twice as deadly to brain stem cells as the variant circulating in Brazil.
Brazilian geneticists reported that the mutations that have taken place between different strains of Zika do not seem to have altered the virus’s ability to cause microcephaly, which they believe may be a universal “feature of Zika itself.” Researchers at Harvard found that when they infected human brain cells with either the original Zika strain isolated in Uganda in 1947 or the strain now circulating in Puerto Rico, the effects were “surprisingly comparable.” And neuroscientists in Florida have demonstrated that infection with the Ugandan Zika strain can cause microcephaly in mice.
Given that the disease is asymptomatic in up to 80 percent of those infected, that only a small fraction of infections during pregnancy result in microcephaly, and that other infections known to cause microcephaly are also widespread (and undiagnosed) across the region, it’s easy to see how an African epidemic of Zika-induced microcephaly could have gone unnoticed, possibly for decades.
Such an oversight would hardly be without precedent. Consider H.I.V., which had been circulating in Africa since at least the 1920s, and not exactly silently; cases of aggressive Kaposi’s sarcoma, the classic AIDS-defining illness rarely found in people without H.I.V., were documented in Uganda as far back as the 1960s. By the time the AIDS epidemic was “discovered” in California in 1981, it was estimated that more than 100,000 people across Africa had already been infected.
Or, for a more recent example, take the explosive spread of Ebola across West Africa starting in 2013. Throughout that epidemic, international health authorities maintained that the virus had never before been seen in Guinea, Liberia and Sierra Leone. Yet six studies published by European scientists in the 1980s had documented that in all three countries, up to 14 percent of the populations studied had Ebola antibodies.
In these and other cases, the warning signs were there. But no one was paying attention.
Epidemiologists call this the “streetlight effect”: the tendency to search for something only where it is easiest to see. When it comes to the study of infectious diseases, parts of sub-Saharan Africa are poorly illuminated: Doctors are scarce, disease surveillance is weak and laboratory capacity is severely limited.
Hence the finding, reported in 2010 by researchers in Cameroon, that “despite documented evidence for their presence in virtually all African countries,” arboviruses (of which Zika is one, of the Flavivirus genus) “are almost never part of routine laboratory diagnoses and very often go unnoticed.” Zika, the authors added, “which had not been previously reported in Cameroon, appears as the most important Flavivirus of humans,” in the area studied, “accounting for more than 11 percent of fevers of unknown origin.” (In May 2016, Belgian doctors reported a confirmed case of Zika in a patient recently returned from Cameroon.)
In September, Congress allocated $1.1 billion to combat Zika in the United States. That’s compared with the $2 million raised by the African Development Bank to support the World Health Organization’s Zika surveillance in parts of Africa. Moreover, to help pay for the American domestic response, Congress cut $109.5 million previously dedicated to strengthening laboratory capacity in parts of West Africa devastated by Ebola — funding that might have helped to define and address the threat of Zika in Africa.
The paradox is that while the development of a Zika vaccine relies heavily on knowledge acquired from Africa, Zika vaccines are unlikely to be prioritized for use there — largely because we have been content to accept flimsy assumptions as scientific facts. Like other diseases before it, the data on Zika seems to matter only when it helps those of us in rich countries protect ourselves. Yet it’s this double standard that allows outbreaks to become pandemics, and that imperils public health — in Africa and everywhere.
Patrick Adams is a freelance journalist who reports on public health. Cameron Nutt is a student at Harvard Medical School.