There isn’t a single new virus dominating headlines right now, but several viruses are causing concern in 2025 due to new outbreaks, evolving strains, or jumps from animals to humans. The most closely watched are H5N1 bird flu (which has infected 71 people in the U.S. through contact with animals), a newer strain of mpox spreading in Central Africa, and Oropouche virus appearing in parts of Latin America. Here’s what each one actually means for you.
H5N1 Bird Flu in Humans
H5N1 avian influenza has been circulating in birds for decades, but what’s new is how often it’s showing up in mammals and, occasionally, in people. The CDC reports 71 confirmed human cases in the United States, with two deaths. The infections have come from direct contact with animals: 41 cases linked to dairy cattle, 24 to poultry farms or culling operations, and a handful from other animal exposures or unknown sources.
The critical detail: there is no known person-to-person spread at this time. Every confirmed case traces back to close contact with infected animals, which means the risk to the general public remains low. The concern is that influenza viruses mutate quickly. If H5N1 picked up mutations allowing efficient human-to-human transmission, it could become a serious pandemic threat. Public health agencies are monitoring the virus closely for exactly that shift, but it hasn’t happened.
Mpox Clade Ib in Central Africa
Mpox (formerly monkeypox) made global headlines in 2022, but the strain circulating then, called Clade IIb, was relatively mild with a fatality rate around 0.2%. A different strain, Clade Ib, has been spreading in the Democratic Republic of the Congo and is drawing fresh attention because of its clinical severity and how it behaves differently in adults versus children.
In a study of over 400 hospitalized patients in South Kivu, 97% had active skin lesions and 82% had mucosal lesions (sores on moist tissues like the mouth or genitals). Among adults, 89% developed genital skin lesions, consistent with sexual transmission being a primary route. Children presented differently, with only 42% showing genital involvement and a more evenly distributed rash across the body. Most infections traced back to close contact with a confirmed or suspected case, whether a spouse, sexual partner, colleague, parent, or sibling.
Two deaths occurred among those 403 hospitalized patients, putting the in-hospital fatality rate below 1%. That’s lower than historical estimates for Clade I strains, which have been associated with fatality rates between 1.4% and 11%. The CDC currently lists mpox outbreaks in Ghana and Liberia at a Level 2 travel notice, meaning travelers should practice enhanced precautions.
Oropouche Virus (Sloth Fever)
Oropouche virus isn’t technically new. It was first identified in Trinidad in 1955. But outbreaks in Brazil, Peru, Cuba, and Panama have brought it to wider attention, and cases in travelers returning to other countries have raised its profile. The CDC has issued Level 2 travel notices for those countries.
The virus spreads through bites from infected midges (tiny flies smaller than mosquitoes) and some mosquito species. After a bite, symptoms develop within 1 to 10 days. Most people experience a dengue-like illness with fever, headache, and muscle pain. In rare cases, the virus invades the nervous system, causing intense pain at the back of the head, confusion, sensitivity to light, stiff neck, and dizziness. There is no vaccine or specific antiviral treatment. If you’re traveling to affected areas, insect repellent and protective clothing are your main defenses.
Marburg Virus in East Africa
Marburg virus causes a severe hemorrhagic fever related to Ebola. Ethiopia experienced its first recorded outbreak, with 14 laboratory-confirmed cases and nine deaths. The virus is carried by a species of fruit bat found in southern Ethiopia, and outbreaks typically start when humans come into contact with bat habitats like caves or mines.
Marburg is not easily transmitted in casual settings. It spreads through direct contact with the blood or bodily fluids of an infected person. The fatality rate in this outbreak was high, roughly 64%, which is consistent with past Marburg outbreaks. For most people outside the affected region, the direct risk is negligible, but the outbreak underscores how animal viruses can spill into human populations without warning.
COVID-19 Is Still Evolving
COVID-19 hasn’t disappeared. The virus continues to mutate, and new variants regularly emerge. As of early 2025, the most prevalent variant under monitoring was XEC, accounting for about 43% of sequenced cases globally. It has been declining in prevalence, and no current variant has shown a dramatic jump in severity compared to previous Omicron-era strains. Updated vaccines continue to target circulating variants, and prior infection or vaccination still provides meaningful protection against severe illness.
Borealpox, Formerly Known as Alaskapox
Six cases of a virus originally called Alaskapox, now renamed borealpox, have been reported in Alaska. The virus has been found primarily in red-backed voles and shrews in the Fairbanks area, and domestic cats and dogs may play a role in carrying it to humans. Symptoms include one or more skin bumps or pustules, swollen lymph nodes, and joint or muscle pain. The number of cases is extremely small, but borealpox is an example of a previously unknown virus emerging from wildlife, which is exactly how most new infectious diseases begin.
What “Disease X” Actually Means
You may have seen references to “Disease X” in news coverage. This isn’t a specific virus. It’s a placeholder used by the World Health Organization and organizations like CEPI (the Coalition for Epidemic Preparedness Innovations) to represent a future pathogen that doesn’t yet cause human disease but could trigger a pandemic. CEPI’s current priority list includes Chikungunya, coronaviruses, Ebola, Lassa fever, mpox, Nipah, Rift Valley fever, and Disease X. The practical purpose of the label is to justify funding for flexible vaccine technologies that can be adapted quickly when a genuinely novel threat appears, rather than scrambling from scratch the way the world did in early 2020.
In short, the viruses making news in 2025 are a mix of familiar threats behaving in new ways and obscure pathogens reaching new populations. None of them currently pose a pandemic-level risk to the general public, but H5N1’s expansion into mammals and the ongoing evolution of mpox Clade Ib are the two situations most likely to change that picture if they continue to evolve.