Argentina is under invasion by a mosquito species carrying a deadly brain disease since the end of December 2023, according to a report by Le Monde.
The biting insects have been found in the capital Buenos Aires and its greater metro area and the country's central region.
The alarming onslaught of an Aedes albifasciatus, also called the flood mosquito, is thanks to the survivability of their larvae in pools or stagnant water which is flooded by rainwater, usually following a drought period, biologist Sylvia Fischer explained.
Argentina has been under the effects of the El Niño weather system, bringing heavy rain after several dry years. That has created perfect conditions for the mosquitoes to thrive.
"The eggs all hatch at the same time, the larvae develop simultaneously, and a huge number of adults emerge at the same time. This is what generates the spike," said Fischer.
Controlling the pests is complicated by their ability to adapt to different temperatures and seasons. The species can fly distances spanning the remotest parts of southern Argentina’s Tierra del Fuego to the country's far north. The invasive species is active by day and night, provided it rains during summer.
One Argentinian woman told how she was bitten five times on her left leg alone while the mosquitoes feasted on other parts of her body. She complained of her discomfort and said the insects could even bite through her clothing.
Able to bite even through the thick skins of livestock, the insects are "a plague, precisely because of its behavior - invasive and aggressive toward people," said Victoria Micieli, a scientist and researcher at Argentina's National Council for Scientific and Technical Research (CONICET) in a report.
The flood mosquito's bites are dangerous to both animals and people as they carry western equine encephalitis — a lethal neurological disease found in horses. Argentina’s Ministry of Health issued a warning on on November 28 last year following an uptick in cases.
By January 5 about 1,250 cases had been confirmed, the ministry said. There are also reports of the disease spreading among horses across most of the country's 24 provinces. Cases of human transmission were reported on January 7, with one death recorded. All the cases among humans are in rural areas.