Dengue cases in the Americas spiked in the first three months of this year by three times the number of infections reported in the same period last year, the Pan American Health Organization said on Thursday.

Brazil, Argentina, and Paraguay are the countries most affected by dengue, in what PAHO officials described at a press conference as probably the worst season to date observed in the Americas for the often deadly mosquito-borne viral illness.

PAHO, part of the United Nations organization, has confirmed some 3.5 million cases of dengue and more than 1,000 deaths this year through March across the Americas, extending from Canada to the southern tip of Chile and including the Caribbean. 

According to Argentina’s latest National Epidemiological Bulletin published over the weekend, 134,202 dengue cases were registered between January 1 and March 17 with 325 serious cases and 106 deaths.

The peak this season was in the ninth week of 2024 (February 26-March 3) with 18,991 cases. The date matches the mosquito invasion that struck Buenos Aires in mid-February.

Around four billion people, or about half the world’s population, live in areas with a risk of contracting dengue, according to data from the U.S. Centers for Disease Control and Prevention.

Dengue symptoms include fever, headaches, vomiting, skin rashes, as well as muscle and joint pain. In some cases, it can cause a more severe hemorrhagic fever, resulting in bleeding that can lead to death.

Most cases of the mosquito-borne disease are usually seen between the late summer months of February and May, but Argentina detected cases throughout the entire 2023/2024 season, even during winter when they usually subside. The National Epidemiological Bulletin shows a steady increase in early October, showing how peak season started sooner.

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—Herald/Reuters