This year delivered many sobering reminders that the coronavirus isn’t the only viral threat out there.

Mpox went global

The mpox virus, a relative of the virus that causes smallpox, had never before spread widely among people outside of Central and West Africa. But in May, mpox, previously known as monkeypox, burst onto the global scene. As of November 28, there have been more than 81,100 cases across 110 countries and 55 deaths.

The disease, which can cause a rash with painful, pus-filled lesions, mainly spreads through close contact. Although anyone can be infected, outside of West and Central Africa the current outbreak is primarily affecting men who have sex with men (SN: 6/18/22, p. 6). Waning immunity worldwide to smallpox — which was eradicated in 1980, ending vaccination programs — likely helped mpox spread. 

In the United States and Europe, cases started going down in August as people at high risk changed their behavior or received vaccines. Preliminary data from the U.S. Centers for Disease Control and Prevention suggest that vaccination is protective. Yet vaccines are still not available in African countries where mpox has historically circulated.

Ebola surged in Uganda

Two small Ebola virus outbreaks were reported in Congo this year. But more worrisome was an outbreak in Uganda that began in September. Current Ebola vaccines and treatments don’t offer protection against the strain causing that country’s outbreak. But clinical trials for three vaccine candidates were set to begin in late 2022.

The outbreak, however, appears to be on the decline after peaking in mid-October. As of December 5, there were no active cases in Uganda. In total, the outbreak has had 142 confirmed cases and 56 confirmed deaths, including at least seven health care workers.

Poliovirus found in sewage

A version of the poliovirus was detected in sewage in New York, Israel, the United Kingdom and some other places where polio had been eliminated, suggesting the virus — which can cause paralysis — was circulating there. In March, Israeli officials confirmed a case of paralytic polio in an unvaccinated 3-year-old; an unvaccinated man in New York was paralyzed by polio in June.

These cases were linked to vaccine-derived polioviruses (SN Online: 9/14/22). One type of polio vaccine relies on live but weakened virus to teach the body to mount immune defenses against the disease. In rare cases, that weakened, or attenuated, virus can spread, mutate and regain the ability to cause paralysis in people who are not vaccinated. Attenuated vaccines are not used in the United States, but are common in some countries, including Afghanistan and Pakistan, the last two places that are still working to eliminate polio.

Unexplained hepatitis hit children

Between October 2021 and July 8, the last time the World Health Organization released an update, more than 1,000 children globally had developed severe hepatitis, an inflammation of the liver. Experts still aren’t sure why. They also don’t know whether it’s a new outbreak, or if doctors are just paying more attention in the wake of the pandemic.

Many cases were linked to an adenovirus, which typically causes colds (SN Online: 5/19/22). But having a previous case of COVID-19 could also factor in. Another hypothesis is that kids with a certain genetic susceptibility are getting hepatitis after a double infection, perhaps with an adenovirus plus a second virus called AAV2.

Bird flu wreaked havoc

Birds around the world also faced a deadly viral foe this year: the H5N1 influenza virus. In the United States alone, more than 4,300 wild birds have tested positive for the virus. A record number of farmed poultry — more than 53 million — died from either infection or being culled to control the virus’ spread. In Europe, the 2021–2022 season was also the largest known epidemic of highly pathogenic avian influenza, with more than 2,600 outbreaks across 37 countries in farmed or captive birds. Researchers are concerned that H5N1 poses a long-term threat to poultry, wild birds and potentially other animals; the virus was linked this year to a seal die-off in Maine.

People can also be susceptible, with two reported cases since December 2021. Although bird flu doesn’t easily spread among people, experts worry that as the epidemic continues the virus will pick up mutations that allow it to transmit from person to person.