In his 20 years cleaning the Buenos Aires subway, Mauricio Ríos, 52, had never seen anything like it: a vast and noisy swarm of mosquitoes churning in dark clouds the length of the platform at Piedras station.

Ríos pulled out his phone and filmed the growing swarm for half a minute, before rushing to the break room, contacting his superior and shutting down the station.

“Mostly in summer time, bugs come down here, attracted by the light, but never in such an enormous numbers,” said Ríos. “They reappeared the next day. I have no idea what’s going on. And, from what I saw in the news, this is not the only place.”

His video quickly went viral as Argentina endures an unprecedented mosquito outbreak, which has been blamed for a spike in dengue, an infectious disease carried by the Aedes aegypti species.

According to the health ministry, 74,555 cases of dengue have been registered in the country since the beginning of the year, a whopping 2,153% higher than the same period in 2023. Forty-seven people have died of it in 2024, and health officials expect cases to continuing surging over the coming weeks.

Dengue’s symptoms include headaches, high fever, vomiting, muscle and joint pains, pain behind the eyes, and a skin rash. Sometimes – especially for those who have been infected more than once – dengue can be severe and lead to death.

According to the head of Córdoba University’s Center of Tropical Diseases, epidemiologist Hugo Pizzi, the outbreak is being caused by a spike in the country’s temperatures – a phenomenon he calls “tropicalization” – together with an increase in out-of-season rains.

“It is the perfect formula for the proliferation of mosquitos,” he said. Pizzi added that mosquitoes are now appearing in the country’s southern provinces, a region where that was unthinkable 25 years ago, due to human-caused climate change.

Even though mosquitoes bite people regardless of their social class, protection is getting increasingly expensive, as the price for mosquito repellent has jumped 170% since December, when the country’s libertarian president, Javier Milei, devalued the peso by 54% and eliminated all price controls. A 290ml canister of spray costs a minimum of 3,620 pesos ($4 at the official rate, $3.60 at the informal rate).

In April last year, Argentina’s health authorities approved a dengue vaccine produced by the Japanese Takeda laboratory that protects against all four dengue serotypes, but its price means it is far from accessible for most people in the country. The government currently has no plans to make the vaccine generally available because it believes more trials are needed, according to a spokesperson for the health ministry.

Milei’s government has blamed the previous administration for the outbreak, saying that former president Alberto Fernández failed to educate the public about the risk. Milei’s campaign manager Fernando Cerimedo has also suggested on X that Bill Gates released the mosquitos intentionally to harm the new government and profit from the dengue vaccines, without providing any evidence.

Pizzi said many Argentinians were still not taking the dire situation seriously, and called on people to clean their yards, eliminate excess water, cut the grass and weeds, and protect their children with mosquito nets. “Small children are defenseless,” he said.

In January, a three-month-old child died of dengue in the northern province of Misiones.

Pizzi called on Argentina’s government – and its population in general – to fight harder against dengue and the insect that carries it. “We cannot be intimidated by a mosquito, by such a tiny creature,” he said.