Experts are raising fresh concerns that the next global pandemic could emerge from viruses related to smallpox, a disease once thought to be permanently defeated.

Scientists say declining immunity and the rise of other poxviruses may pose a serious future risk.

Health experts have warned that deadly smallpox, or similar viruses from the same family, could potentially trigger the next pandemic.

Smallpox, medically known as variola, was officially eradicated in 1980 following a worldwide vaccination campaign led by the World Health Organization (WHO). Its elimination was considered one of humanity’s greatest public health achievements.

Although smallpox no longer circulates naturally, the virus has not completely disappeared.

Today, samples of the virus are preserved under strict security in a small number of high-level laboratories. These samples are tightly controlled and rarely accessed, making natural outbreaks extremely unlikely.

Declining immunity raises new concerns

Scientists now say the eradication of smallpox has had an unintended consequence.

With routine smallpox vaccination stopped decades ago, immunity against other related viruses has gradually weakened. Experts warn this reduced protection could open the door to new infections from the same viral family.

Smallpox belongs to the orthopoxvirus family, which includes several other viruses capable of infecting humans.

These include monkeypox, as well as lesser-known viruses such as boreal pox, buffalo pox, and camel pox. Experts fear that one of these viruses could adapt, spread more efficiently, and replace smallpox as a major global threat.

Deadly historical reminder

The warnings are grounded in history.

During the 20th century alone, smallpox is estimated to have killed around 500 million people worldwide. Its rapid spread and high fatality rate made it one of the deadliest diseases ever known.

Scientists stress that while smallpox itself remains rare, the conditions that once allowed it to spread widely could re-emerge in a different form.

They caution that vigilance is needed as orthopoxviruses continue to circulate, especially in populations with little to no immunity.