What about the Zika Virus?
As you will recall, in 2016 the Zika virus, and the devastating birth defects it causes, exploded in Latin America and the Caribbean, and this spilled over to the U.S. There were 5,000 Zika cases reported in the U.S. from travelers who were bitten by mosquitoes in other parts of the world and returned here with the virus, plus another 224 cases of local transmission where people were bitten and contracted the disease in Florida and Texas.
But in 2017, there were only about 367 travel-related cases of Zika in the U.S. There were only two cases of suspected local transmission, plus another four cases where the virus was acquired through sexual transmission. This reduction was seen in other areas of the world as well. For instance, Puerto Rico had 35,000 Zika cases in 2016, but less than 500 in 2017. This type of drop-off in infections is a pattern that has occurred with other viruses similar to Zika—when some of the human population is exposed and develops an immunity, the percentage of susceptible people to infect drops, and the virus loses steam.
Zika will continue to be a highly important mosquito-transmitted virus to be cautious about. There will likely be occasional flare-ups in different areas, and no one knows how long the immunity will last. If many people in a region lose their immunity, we may have more very dangerous outbreaks. It is important to remain vigilant about this mosquito-borne virus because it causes not only birth defects, but also ongoing neurological effects in adults.