A disease vector is anything—such as a rat or a mosquito—that spreads diseases, especially diseases that aren’t contagious on their own, from one human to another. The disease-causing agent, which is typically a parasite but can also be a virus or even a bacterium, instead alternates between humans and vermin. Worldwide, 17 percent of infectious disease cases are vector-borne diseases. These diseases generally spread in areas where access to safe drinking water is spotty at best and sanitation systems are unreliable or nonexistent. Often, they are found in developing countries in tropical and sub-tropical regions, but vector-borne diseases such as malaria have been common in the American South in living memory.
That means that it’s important for people who are in or planning to be in areas where these diseases are common to be prepared. Travelers should talk to heath care providers about needed immunizations—it’s easy to forget that a disease nearly unheard of in the United States or in colder climates can be an ever-present danger in another part of the world. Nets are often effective against mosquito-borne diseases.
In addition, efforts are underway to eradicate these illnesses completely. There are three approaches that are taken: destroying the populations of the creatures that spread them, keeping those creatures away from humans, or keeping animals from becoming carriers. If humans don’t get infected, in many cases, the carrier animals won’t get infected either, and won’t spread diseases to other humans. To this end, in many places governments and relief organizations have undertaken projects to kill mosquitoes and other insects that spread disease or to improve sanitation so that there is no disease to be spread. Vaccination programs also help, by keeping people from passing the illness back to animals.
However, partial eradication isn’t enough. Dengue fever, for example, was at an all-time low a few decades ago, but as interest in combating it waned, it gradually came to be one of the biggest threats among vector-borne diseases. Better sanitation, particularly water, eradication of vectors such as through insecticide spraying, and vaccinations are the pillars on which eradication efforts rest.