These Are The 3 Viruses To Watch In 2026, Disease Expert Says

In an article for The Conversation, Patrick Jackson, Assistant Professor of Infectious Diseases at the University of Virginia, highlighted three that he would be keeping a particular eye on in 2026: influenza A, mpox, and Oropouche virus.

"A warming and increasingly populated planet puts humans in contact with more and different viruses,” he wrote. “And increased mobility means that viruses can rapidly travel across the globe along with their human hosts."

Here’s the lowdown on his top picks, and why Jackson isn’t the only one to be worried.

Influenza A

In 2024, H5 influenza appeared in US dairy cattle for the first time and quickly established itself in herds in multiple states. Since then, the Centers for Disease Control and Prevention (CDC) has reported 71 cases in humans and two deaths.

The first was a Louisiana resident infected with H5N1 who died in January 2025, while the second lived in Washington state and is the first person known to have contracted the related H5N5 strain.

Dairy and poultry workers make up almost all cases, and there has been no human-to-human transmission in the US. The November case was also the first since February 2025, marking a nine-month gap in human infections.

That is somewhat reassuring, and the CDC maintains the public health risk is low, but Jackson isn’t alone in his concerns. "That species breadth is a hallmark of a dangerous pathogen that could emerge," Derek Cummings, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, told U.S. News & World Report in January.

There is also doubt over whether the CDC can effectively track the prevalence and spread of the disease after funding and staffing cuts by the Trump administration, which have reportedly led to much of its flu surveillance infrastructure being shut down.

"How much of it is because it's not happening, versus how much of it is because it's not being reported, versus how much of it is because the government is not reporting it to us?" Angela Rasmussen, a virologist at the University of Saskatchewan, told the Los Angeles Times.

Mpox

Mpox virus – formerly called monkeypox – has been a concern in Africa since it was first documented in the 1970s, but it has only recently gained widespread attention in the West.

"Mpox is closely related to smallpox, and infection results in a fever and painful rash that can last for weeks," said Jackson. It is divided up into four groupings, or subclades, known as Ia, Ib, IIa, and IIb.

In 2022, an outbreak of clade IIb spread to over 100 countries through human-to-human transmission, mainly through sexual contact. While case numbers have since declined and the public health emergency was declared over, the outbreak continues, and in 2023 it was joined by a clade Ib outbreak that began in the Democratic Republic of the Congo and spread to multiple neighboring countries by 2024.

While clade I has yet to spread as widely as clade II, the CDC has reported 10 cases of it in the US since 2024, including three cases of clade Ib mpox in California. There had been 19 cases of clade Ib mpox in the UK as of November 30, 2025.

Most individuals in these cases reported either direct or indirect links to travel to countries where mpox is circulating, but the evidence suggests there is now also some person-to-person transmission occurring outside of Africa.

At the start of the 2022 outbreak, epidemiologists in Africa lamented the lack of attention on mpox from elsewhere. Adesola Yinka-Ogunleye at the Nigeria Centre for Disease Control in Abuja told Nature News, “the world is paying the price for not having responded adequately” to earlier outbreaks, including on in Nigeria in 2017.

In its January 2026 report, the CDC said it expects “additional cases in Europe and the United States”. While most cases are mild and will resolve on their own after a few weeks − and there is a vaccine available – there is no specific treatment.

Oropouche virus

First identified in Trinidad in the 1950s, Oropouche is an insect-borne infection carried primarily by biting midges (Culicoides paraensis). It is thought to have originated in sloths, hence sometimes being dubbed “sloth fever”.

Once confined to the Amazon, cases began appearing throughout South and Central America in the 2000s, and, during an outbreak in 2024, travel-related cases were reported in Europe for the first time, as were the first-ever deaths in Bahia, Brazil.

“The biting midge that carries Oropouche virus is found throughout North and South America, including the southeastern United States,” said Jackson. “The range of the virus could continue to expand.”

During the 2024 outbreak, there were also reports of vertical transmission − from mother to child − and the virus was linked to cases of microcephaly, a condition in which a baby's head develops to be smaller than expected.

In response to the uptick in cases and increased range of Oropouche, the World Health Organization published a report on January 5, 2026 outlining a research and development roadmap to tackle the disease.

One of the priorities it outlines is the development of vaccines and therapeutics, of which Oropouche currently has none.

Other diseases

These are just three examples, but there are plenty more pathogens out there with the potential to spread further or into new regions under the right – or wrong – circumstances.

Chikungunya virus is one of Jackson’s honorable mentions. The mosquito-borne virus has symptoms similar to dengue and Zika, and it had a resurgence in several countries last year, with 445,271 suspected and confirmed cases and 155 deaths between 1 January and 30 September 2025.

A recent outbreak of Nipah virus in West Bengal has also drawn attention, but so far researchers have said there is little cause to be worried about it developing into a large epidemic or pandemic.

Professor Piero Olliaro at the University of Oxford told the UK Science Media Centre on January 28 that "based on available information, the current outbreak does not appear larger or more severe than previous Nipah outbreaks" and that "the virus does not currently exhibit the transmissibility needed to cause a pandemic”.

The response to the outbreak was described by Dr Efstathios Giotis at the University of Essex as “swift and targeted”.

Nipah, alongside all the previously mentioned viruses, is listed on WHO’s priority pathogen list, which acts as a guideline for where the world’s resources should be allocated to most effectively guard against the spread of disease. The response in West Bengal should perhaps provide some reassurance that this system is working.

On the other hand, even diseases we should be able to tackle are staging comebacks. Measles has rebounded in recent months amid falling vaccination rates, with several countries losing their elimination status. The US is expected to lose its measles elimination status in April at a meeting convened by the Pan American Health Organization.

As Jackson notes, health professionals must always stay alert: "Around the world, people, animals and the wider environment are dependent on each other. Vigilance for known and emerging viral threats and the development of new vaccines and treatments can help keep everyone safe."