The viruses that shaped 2024

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The viruses that shaped 2024

This year saw record-breaking surges in dengue and mpox cases, a polio outbreak in Gaza, and the emergence of new viral threats.

Dengue cases reached unprecedented levels. Dengue fever, a mosquito-borne disease, broke global records in 2024. The Americas alone reported approximately 12.7 million cases by early December, 90% of the world’s estimated 14 million total cases. This staggering number more than doubles the previous record of 5.3 million cases reported globally by the WHO in 2023.

Experts point to climate change, El Niño, and urbanization as driving factors behind the outbreak. Rising temperatures are estimated to have increased dengue transmission by 18% in the Americas and Asia.

Projections suggest that if warming trends continue, transmission could rise by 40–57% by 2050.

Mpox declared a global emergency
An escalating mpox outbreak in Central Africa prompted the World Health Organization (WHO) to declare a public health emergency of international concern in August. Mpox, known for its fever, muscle aches, and painful rash, has long affected Africa, particularly the Democratic Republic of Congo (DRC), where the current outbreak originated.

In 2024, the virus spread to previously unaffected countries, including Burundi, Kenya, Rwanda, and Uganda. By December, nearly 60,000 cases and 60 deaths had been reported across 20 countries. Children were disproportionately impacted.To curb the spread, over 170,000 vaccine doses were distributed to Nigeria, Congo, and Rwanda. The UN also authorized the first mpox vaccine for children aged one and older.

Bird flu jumped to dairy cows
The global H5N1 bird flu outbreak took a surprising turn in March when the virus spread to dairy cows in the United States. Over 700 herds across 16 states were affected, with symptoms including reduced milk production. Studies indicate that contaminated milking equipment facilitated cow-to-cow transmission.

By December, 58 farm workers had tested positive for H5N1. Alarmingly, one Missouri resident contracted the virus without direct exposure to cows or poultry, hinting at rare person-to-person spread through close contact. While the risk to humans remains low, scientists are monitoring for mutations that could enhance transmissibility.

Polio resurfaced amid conflict in Gaza
In September, a polio outbreak in Gaza prompted a massive vaccination campaign after the virus was detected in wastewater and a 10-month-old boy developed paralysis. The WHO fully vaccinated 556,774 children (94% coverage) by November. However, ongoing conflict and displacement hindered access in northern Gaza, leaving up to 10,000 children vulnerable.

Oropouche fever spread and turned deadly
Oropouche fever, a viral disease transmitted by biting midges, emerged in new areas across South America and the Caribbean. First-ever cases were reported in Guyana, Cuba, and the Dominican Republic, as well as several Brazilian states. For the first time, the virus caused fatalities, including two deaths and a stillbirth in Brazil.

Triple E cases on the U.S. East Coast
Eastern equine encephalitis (Triple E), a mosquito-borne virus, resulted in 16 cases across eight U.S. states in 2024. While most infections go unnoticed, severe cases—where the virus invades the nervous system—are often fatal. 

This year, all reported cases were neuroinvasive, with three deaths recorded. (Source: ScienceNews)