As we enter a new year, there may be new viral threats on the horizon.
Viruses are constantly changing and adapting. With a warming world and growing populations, humans encounter a greater variety of viruses. Plus, the way we travel means these viruses can spread rapidly around the globe.
As someone involved in infectious diseases, I plan to keep an eye on a few specific viruses in 2026 that could lead to infections in surprising places or numbers.
Influenza A – a potential pandemic threat
Influenza A is always a concern. This virus has a wide host range and can mutate quickly. The last pandemic, triggered by the H1N1 strain in 2009, resulted in over 280,000 deaths globally in its first year, and it continues to exist today. Initially spread from pigs in Mexico, it became widely known as swine flu.
Currently, scientists are monitoring the H5N1 subtype of avian influenza. First identified in humans in southern China in 1997, this virus has spread globally, primarily through wild birds. In 2024, it was detected in dairy cattle in the U.S., establishing itself in several herds.
The concern is that the virus could adapt to humans. There have been reports of cow-to-human transmissions, and in 2026, researchers will continue to assess whether H5N1 could potentially be transmitted between humans, which is critical for a new pandemic to start. The existing influenza vaccines may not protect against H5N1, but efforts are underway to create effective vaccines.
Mpox – a global concern
Mpox, previously known as monkeypox, was first discovered in the 1950s but remained rare, primarily seen in sub-Saharan Africa. Ironically, its main carriers are rodents rather than monkeys, and it occasionally crosses into humans.
Related to smallpox, infection can lead to a fever and a painful rash lasting several weeks. Various strains exist, with clade I being more severe than clade II. Though a vaccine is available, effective treatments are lacking.
In 2022, a global outbreak of clade II mpox spread to more than 100 countries, mainly due to human-to-human transmission during close contact, often through sexual activity. While cases have dropped since then, clade II mpox remains prevalent worldwide. Some regions in Africa have also reported a rise in clade I cases since 2024, and since August 2025, four clade I cases were reported in the U.S. – notably in individuals who had not visited Africa.
The trajectory of mpox cases in and outside the U.S. remains uncertain as we move into 2026.
Oropouche virus – an emerging threat
The Oropouche virus was first identified in the 1950s in Trinidad. It’s transmitted by mosquitoes and small biting midges, commonly known as no-see-ums.
Most infections lead to fever, headaches, and body aches. While symptoms typically last only a few days, some patients may experience lingering weakness for weeks, and in some cases, the illness reoccurs after recovery.
There are still many unknowns regarding Oropouche virus and the disease it causes, and no specific treatments or vaccines exist. Historically, cases were thought to be confined to the Amazon, but since the early 2000s, reports have emerged from a broader area of South and Central America and the Caribbean, often tied to travelers returning home.
Looking ahead to 2026, Oropouche outbreaks are likely to continue affecting travelers in the Americas, where the biting midges that carry the virus are prevalent, particularly in the southeastern U.S. The virus’s range may further expand.
Additional viral concerns
Several other viruses also present risks going into 2026.
Ongoing chikungunya outbreaks might impact travelers, prompting some to consider vaccination.
Measles cases are rising in the U.S. and worldwide amid falling vaccination rates.
Despite effective treatments, HIV appears ready for resurgence, partly due to interruptions in international aid.
Lastly, as always, new and unpredictable viruses may emerge as a result of human activities and travel.
Ultimately, the intricate relationship between people, animals, and the environment underscores the need for vigilance against both known and emerging viral threats, and for the development of new vaccines and treatments to ensure public safety.
