The world faces potential crises from three viruses in 2026, according to infectious disease experts. These include the avian influenza A (H5N1), the mpox virus and the Oropouche virus.
Patrick Jackson, an adjunct professor of Infectious Diseases at the University of Virginia, highlighted the need for vigilance regarding these viruses, noting they have all expanded their reach and could be poised to make further significant jumps. “Even though very distinct from each other, all share an unsettling trait: they have crossed new borders and expanded their reach,” Jackson explained.
The Oropouche virus, transmitted by mosquitoes, is a growing concern. Originally identified in Trinidad in the 1950s, it was long considered confined to the Amazon region. However, since the 2000s, it has spread throughout South America, Central America, and the Caribbean. In 2024, Brazil documented the first deaths associated with the virus, and cases linked to travelers were reported in Europe. Researchers are also investigating potential links to microcephaly and have documented instances of vertical transmission – from mother to child. The mosquito vector has adapted to wide areas of the continent, including the southeastern United States, and currently, there are no vaccines or specific treatments available.
In response, the World Health Organization (WHO) presented a roadmap on January 5, 2026, to accelerate the development of prevention and control tools against Oropouche.
The H5N1 avian influenza virus, historically a threat due to its rapid mutation rate, has recently shifted focus. In 2024, it was detected in dairy cows in the United States, marking a species jump that raised concerns among experts. The virus reappeared in herds across multiple states, and studies suggest numerous transmissions from cows to humans, often without apparent symptoms. The primary concern is the virus adapting to transmit efficiently between humans, a necessary step for a potential pandemic.
As of early 2026, the Centers for Disease Control and Prevention (CDC) has reported 71 human cases and two deaths in the U.S. Since 2024, with no evidence of sustained community transmission. Development of specific vaccines is underway, as current influenza vaccines are unlikely to provide sufficient protection against this strain.
Mpox, formerly known as monkeypox, was a rare disease confined to parts of Africa for decades. A global outbreak of the IIb clade in 2022 changed that, spreading to over one hundred countries, largely through close physical contact, including sexual contact. This variant now circulates recurrently in various countries. Simultaneously, an increase in infections from the more severe clade I has been reported in Central African countries, with recent cases of clade Ib identified in the U.S. In individuals with no travel history to Africa. While a vaccine exists, there is no specific treatment, and experts caution that the virus’s evolution throughout 2026 could present new challenges.
Beyond these three, other viruses are also drawing attention. Chikungunya caused over 445,000 suspected and confirmed cases in 2025, with at least 155 deaths reported as of September. The Nipah virus is also under surveillance following a recent outbreak in West Bengal, though specialists currently believe it does not pose a pandemic threat. Measles is experiencing a resurgence in several countries due to declining vaccination rates, potentially jeopardizing elimination status in places like the United States. Some experts also warn that diseases like HIV could see a resurgence if international health cooperation programs continue to be cut.
