The viral threats everyone should watch in 2026

Viruses are constantly evolving, and a warming, increasingly populated planet is bringing humans into closer contact with a wider range of pathogens. At the same time, global travel allows viruses to spread rapidly across continents alongside their human hosts.

As an infectious diseases physician and researcher, several viruses stand out in 2026 as potential threats—either because they may appear in unexpected places or because they could infect larger numbers of people than anticipated.

It remains one of the most persistent global health threats. The virus infects many animal species and mutates rapidly, allowing it to jump between hosts and evade immunity.

The most recent influenza pandemic, caused by the H1N1 subtype in 2009, killed more than 280,000 people worldwide in its first year. That virus, commonly known as swine flu, originated in pigs before spreading globally and continues to circulate today.

More recently, scientists have been closely monitoring the highly pathogenic avian influenza subtype H5N1 avian influenza, often called bird flu. First identified in humans in southern China in 1997, the virus spread globally via wild birds. In 2024, H5N1 was detected for the first time in dairy cattle in the United States and later became established in herds across several states.

The virus’s jump from birds to mammals has raised serious concern. Studies suggest that cow-to-human transmission has already occurred multiple times. In 2026, scientists will be watching closely for any evidence of sustained human-to-human transmission—a critical step towards a new influenza pandemic.

Current seasonal flu vaccines are unlikely to provide protection against H5N1, but efforts are under way to develop vaccines specifically targeting the virus.

Formerly known as monkeypox, was first identified in the 1950s and for decades was largely confined to parts of sub-Saharan Africa. Despite its name, the virus primarily infects rodents and only occasionally spreads to humans.

Mpox is closely related to smallpox and causes fever and a painful rash that can persist for weeks. There are several forms of the virus, including the more severe clade I and the generally milder clade II. A vaccine is available, but no specific antiviral treatment exists.

In 2022, clade II mpox caused a global outbreak, spreading to more than 100 countries that had never previously reported cases. Transmission occurred primarily through close physical contact, including sexual contact.

Although case numbers declined after 2022, mpox has now become established worldwide. Since 2024, several central African countries have reported rising clade I infections. Since August 2025, four clade I cases have been identified in the United States, including among individuals with no travel history to Africa.

How mpox will evolve in 2026—both within Africa and globally—remains uncertain.

The virus was first identified in the 1950s on the island of Trinidad. It is transmitted by mosquitoes and small biting midges, commonly known as no-see-ums.

Symptoms typically include fever, headache and muscle pain. Most cases resolve within days, but some patients experience prolonged weakness, and relapses can occur. There are no vaccines or specific treatments.

For many years, human infections were thought to be limited to the Amazon basin. Since the early 2000s, however, cases have spread across South America, Central America and the Caribbean. In the United States, most infections have been identified in returning travellers.

The insect vectors that transmit Oropouche virus are widespread across the Americas, including the southeastern United States. In 2026, outbreaks are likely to continue among travellers, and the virus’s geographic range may expand further.

Several additional viruses could pose challenges in 2026.

Ongoing outbreaks of Chikungunya virus may affect travellers, some of whom may benefit from vaccination where available.

Measles cases are rising globally, including in the United States, largely driven by declining vaccination rates.

HIV may also see a resurgence in some regions due to disruptions in international aid, despite the availability of effective treatments.

Beyond known threats, new viruses will inevitably emerge as human activity continues to disrupt ecosystems and increase global connectivity.

Humans, animals and the environment are deeply interconnected. Vigilance, robust surveillance systems, sustained vaccination programmes and continued investment in treatments and research will be essential to reducing the impact of both familiar and emerging viral threats in the year ahead.

Subscribe to our newsletter and stay updated on the latest developments and special
offers!