Last week, India publicly announced three laboratory-confirmed cases of Zika infection. The occurrence of Zika infection in India is not surprising, as the Aedes aegypti mosquito, the vector known to spread Zika, is present in abundance in the country. In addition, a serology study found evidence of human Zika infection in India in 1952—5 years after the virus was first discovered, isolated from nonhuman primates in Uganda.
However, what is newsworthy about these three cases—and has been reported widely—is that they were discovered by local health officials in November 2015 but not reported to the World Health Organization until mid-May 2017. Though local officials did take measures to respond to the discovery of these three infections—they are reported to have deployed vector control measures and increased human and vector-based surveillance efforts in order to identify new cases—an official with India’s health ministry told The New York Times that concerns about public panic factored into their decision to not publicly disclose the cases.
Prompt reporting and information sharing are critical to tracking epidemics and enabling the public to make risk-based decisions and take appropriate protective actions; however, it is important to remember that places reporting Zika transmission may experience powerful economic disincentives against timely reporting. The World Bank estimated that the short-term economic costs of the Zika epidemic to the Latin American and Caribbean regions could be as high as US$3.5 billion, or 0.06% of the entire region’s GDP. Similarly, when Zika cases began to be reported in Miami, Florida, there were deep concerns about what the virus would do to the local economy—specifically, Miami’s $24 billion tourism industry—once the CDC and other countries’ health officials issued travel advisories for the affected area. Some countries, including the United States, had already published Zika-specific travel precautions for India in advance of the recently announced cases, specifically that pregnant women should avoid traveling to the country based on concern that “Zika has likely been present…for years with ongoing transmission.” Few countries have issued formal Zika-related travel notices for India; however, others, including the United Kingdom, have upgraded India’s Zika risk assessment in light of the recent reports and published new travel precautions for pregnant women. Even if not in the form of formal travel notices, recommendations for pregnant women to avoid travel to India could also prompt other prospective travelers to cancel upcoming travel plans, potentially resulting in significant damage to India’s economy.
Lack of sufficiently effective tools to control the spread of infection may also fuel governments’ hesitancy to disclose cases or even conduct thorough surveillance for the virus. Absent a vaccine to prevent or medicines to treat infection, the best remaining option for reducing transmission is vector control measures. But while the WHO acknowledges that vector control in response to Zika cases can be important in helping to reduce the spread of the virus, they sanguinely note that “mosquito control is complex, costly, and blunted by the spread of insecticide resistance.” The WHO also notes that “few developing countries…have dedicated well-funded programmes for mosquito control.” Additionally, documented public opposition to some common vector control measures, such as the use of insecticides and larvicides, poses further challenges to vector control efforts.
Taken together, the economic disincentives and lack of better public health control measures suggest that India is likely not alone in its hesitation to publicly announce its Zika cases. Indeed, local elected officials in Florida have also criticized the degree to which state health officials released information about Zika vector surveillance efforts.
On a related note, the CDC recently removed Miami-Dade County from list of places that it cautions pregnant women from visiting. This decision was based on the fact that no new infections have occurred for 45 days (~3 incubation periods). But as the US is about to head into the summer, when the risk of acquiring a mosquito-borne infections typically increases, health authorities will have to remain vigilant and reassess the situation throughout mosquito season.