How monkeypox symptoms compare to smallpox and chickenpox

• More than 100 cases of monkeypox have been detected worldwide in the past month, including in the US.
• Monkeypox symptoms can be confused with those of chickenpox.

Health officials around the world have urged people to be alert to monkeypox rashes, as more than 100 cases have been confirmed in the past month and an additional 131 are suspected, according to the World Health Organization.

Inger Damon, director of the Centers for Disease Control and Prevention's Division of High-Consequence Pathogens and Pathology, said in a statement after the first case was confirmed in the US: "Healthcare providers should be alert to any rash that has features typical of monkeypox. We're asking the public to contact their healthcare provider if they have a new rash and are concerned about monkeypox."

But identifying a monkeypox rash is not always easy.

Although they are caused by different types of viruses, the symptoms of monkeypox are similar to those of chickenpox — and it can be tricky to tell between the two without a test.

In Greece, for example, local media reported on Monday that the country's first suspected monkeypox case tested positive for chickenpox and not monkeypox.

Symptoms of monkeypox can also be compared with smallpox — a related virus that was declared eradicated in 1980. Like smallpox, monkeypox causes pus-filled boils.

Monkeypox, however, is generally milder than smallpox, with symptoms getting better on their own within two to four weeks. Monkeypox is less contagious than smallpox was and less fatal, according to the WHO.

The main difference between the symptoms of smallpox and monkeypox is swollen lymph nodes or "lymphadenopathy" — monkeypox causes lymph nodes to swell while smallpox does not, according to the CDC.

Here are the symptoms associated with monkeypox and how they compare with chickenpox and smallpox.