A mounting number of citations on a popular disease-tracking website suggests that mosquitoes may be moving into new ecological niches with greater frequency.
The website, ProMED mail, has carried more than a dozen such reports since June, all involving mosquito species known to transmit human diseases.
Most reports have concerned the United States, where, for example, Aedes aegypti — the yellow fever mosquito, which also spreads Zika, dengue and chikungunya — has been turning up in counties in California and Nevada where it had never, or only rarely, been seen.
Other reports have noted mosquito species found for the first time on certain South Pacific islands, or in parts of Europe where harsh winters previously kept them at bay.
ProMED, the Program for Monitoring Emerging Diseases, is overseen by the International Society for Infectious Diseases. Its moderators disseminate alerts coming in from members, news media, government releases and other sources, with notes that put these reports in context and separate the truly alarming from the merely alarmist.
Over the years, the site has chronicled Public Health England’s hard-fought battle to keep a new invader, Aedes albopictus, the Asian tiger mosquito, out of the “scepter’d isle” that Shakespeare in “Richard II” called “this fortress built by Nature for herself against infection.”
Aedes albopictus established itself in Italy and southern France, where it has spread chikungunya — a painful fever known as “bending up disease.” British health authorities now have more than 30 surveillance stations at ports, airports and truck stops, on guard against the mosquito.
In August, The Daily Express newspaper said officials had “blitzed a clutch of notorious tiger mosquitoes suspected to have smuggled their way into Britain through the Eurotunnel.”
In 2014, ProMED noted, Public Health England debunked false alarms that the mosquito had landed. In 2016, officials acknowledged finding 37 Aedes albopictus eggs at a truck stop in Kent.
Also in August, ProMED reported that Aedes albopictus appeared to have established itself in Gibraltar, a British territory on the southern edge of Spain.