Four Viral Threats Experts Are Watching Closely in 2026—And Why You Should Know About Them

As the planet warms and travel accelerates, viruses are spreading faster and jumping between species in ways that alarm infectious disease experts. Four particular threats are on the radar for 2026: H5N1 bird flu, which has now infected U.S. dairy cows; mpox (formerly monkeypox), which is quietly spreading in new forms; Oropouche virus, a tropical infection creeping northward; and measles, which is resurging due to declining vaccination rates.

Why Is H5N1 Bird Flu Such a Pandemic Concern?

Influenza A, particularly the H5N1 strain, remains the virus experts watch most closely as a potential pandemic threat. H5N1 first appeared in humans in 1997 in southern China, but it mostly stayed in birds—until 2024, when it was detected in U.S. dairy cows for the first time. The virus didn't stop there. H5N1 is now entrenched in multiple herds across several states, marking a significant shift in how this virus behaves.

What makes this especially alarming is that mammal-to-human transmission has now been documented. Cows have passed the virus to people. However, there's currently no sign that H5N1 is spreading efficiently from human to human—but that's the critical barrier virologists are watching. Once that final leap happens, we enter pandemic territory again.

The standard flu shots most people get each fall probably won't protect against H5N1. Researchers are racing to develop targeted vaccines, but as of now, we're in what experts call a high-stakes waiting game. This is notably different from the 2009 H1N1 outbreak, sometimes called "swine flu," which started in Mexico, spread globally within weeks, and killed over 280,000 people in its first year.

What's Happening With Mpox, and Why Has It Faded From Headlines?

Mpox (previously known as monkeypox) exploded into public consciousness in 2022, suddenly appearing in over 100 countries after being largely confined to sub-Saharan Africa for decades. The virus causes a painful, blistering rash and flu-like symptoms and is part of the same viral family as smallpox.

Many 2022 cases involved a milder strain called Clade II, which spread largely through close physical contact. Public health officials managed to curb its reach temporarily. But here's the critical issue: viruses don't retreat just because we stop paying attention. Since 2024, countries in Central Africa have reported rising cases of Clade I, the more severe version of mpox. Even more concerning, the U.S. has now reported four Clade I cases in people who hadn't traveled abroad, suggesting the virus may be spreading quietly in ways we haven't fully traced.

The mpox vaccine still exists, but global supplies remain limited. Unlike with COVID-19 or the flu, we don't currently have effective treatments. If mpox mutates to become more contagious or takes off again in a new population, public health systems will need to move fast with limited tools.

How to Stay Informed About Emerging Viral Threats

• Monitor Travel Advisories: Check health agency updates before traveling to regions where tropical viruses like Oropouche, chikungunya, or mpox are spreading, and ask your doctor about available vaccines or preventive measures.
• Maintain Vaccination Status: Keep your flu, measles, mumps, and rubella (MMR), and other routine vaccines current, as declining vaccination rates are allowing previously controlled diseases to resurge.
• Track Emerging Virus News: Follow updates from the Centers for Disease Control and Prevention (CDC) or World Health Organization (WHO) about new or resurgent viruses, especially those spreading in regions near you or affecting your travel plans.
• Practice Basic Prevention: Use insect repellent in areas with mosquitoes or biting midges, practice good hand hygiene, and avoid close contact with people showing signs of illness, especially during respiratory virus seasons.

What Is Oropouche Virus, and Why Should North Americans Care?

Oropouche virus is one you've probably never heard of, and that's part of the problem. It doesn't get much media coverage, but it's slowly spreading and could become a much bigger problem than we're prepared for. First identified in the 1950s off the coast of South America, Oropouche is carried by mosquitoes and biting midges (tiny insects known as "no-see-ums").

The virus causes a short-lived but nasty illness: fever, headaches, muscle pain, and in some cases, lingering weakness lasting weeks. Most infections have historically clustered around the Amazon, but over the last couple of decades, that's changed dramatically. Cases are now appearing across South and Central America, as well as the Caribbean, often in places where no one expected it to show up.

Here's the kicker: travelers returning to the U.S. have brought the virus with them. The tiny bugs that carry Oropouche are found throughout much of North America, including the southeastern U.S. There are no vaccines or treatments for Oropouche, and it hasn't caused large outbreaks in North America yet. But all the ingredients are present. In a warming world with longer mosquito seasons, the line between tropical disease and domestic threat is getting blurrier every year.

Which Other Viruses Are Making Unexpected Comebacks?

Beyond the three major threats, several other viruses are resurfacing in concerning ways. Chikungunya is spreading in parts of the world where it was previously rare. Measles, once nearly eradicated in the U.S., is seeing a sharp rise in cases thanks to declining vaccination rates—a stark reminder that even "solved" problems can resurface. And HIV, despite the existence of highly effective treatment and prevention methods, is still spreading largely due to international funding gaps, healthcare access issues, and ongoing stigma.

We also can't ignore the unknowns. As humans continue to disrupt natural habitats, encroach on wildlife, and hop continents with ease, new viruses are almost certain to emerge. The next big threat might not be on our radar yet, but that doesn't mean it's not already brewing.

Are We Actually Prepared to Handle These Threats?

If all of this sounds grim, that's not the full picture. The truth is, we're better equipped than ever before to detect, track, and fight viral threats. We have genomic surveillance, global networks of scientists, rapid vaccine development platforms, and public health systems that, while far from perfect, can still respond quickly when given the right resources.

But awareness matters. Staying informed isn't fear-mongering; it's preparedness. Viruses don't announce themselves with flashing lights. They creep in quietly, hitching rides on the backs of birds, cows, mosquitoes, or human travelers. The goal isn't to panic. It's to pay attention. Because the sooner we notice them, the sooner we can stop them.