(NEXSTAR) – The World Health Organization said mpox is spreading so rapidly in parts of Africa that it constitutes a global health emergency. For many in the U.S., the virus hasn’t been top of mind for a couple of years, but is there now renewed cause for concern?

There are several important differences between the type of mpox that was spreading globally (including around the U.S.) in 2022 and the type of mpox that prompted the WHO’s new declaration.

The WHO said so far there have been more than 14,000 cases and 524 deaths in Africa this year, which already exceed last year’s figures. More than 96% of all cases and deaths are in a single country: the Democratic Republic of the Congo.

The strain of mpox spreading now (clade I) is more serious than the type we saw two years ago (clade II), the Centers for Disease Control and Prevention explains. Clade I spreads more easily and could kill up to 10% of people who contract it. On the other hand, more than 99% of people who caught the clade II version in 2022 survived.

Also, in previous mpox outbreaks lesions were mostly seen on the chest, hands and feet. The new form of mpox causes lesions on the genitals and milder symptoms. That may sound like a good thing at first, but it actually makes an infection harder to spot, meaning people might also sicken others without knowing they’re infected.

During the global outbreak of mpox in 2022, gay and bisexual men made up the vast majority of cases and the virus was mostly spread through close contact, including sex. But with this outbreak in Congo, a majority of cases and deaths are in children. The reasons for the difference aren’t entirely clear. It could be because kids are more susceptible, said Dr. Boghuma Titanji, an infectious diseases expert at Emory University. Social factors, like overcrowding and exposure to parents who caught the disease, could also be at play.

Another key difference between now and 2022: No cases of clade I mpox have been reported in the U.S. yet, according to U.S. Health and Human Services.

The CDC believes the risk of the clade I mpox coming from Congo into the U.S. is “very low,” and says even if the new strain did find its way here, our country is well prepared to combat its spread. Importantly, we already have a vaccine that works.

“Based on what we know, people in the United States who have already had mpox or have had both doses of mpox vaccine are likely to be protected against clade I mpox,” the CDC writes.

Anyone who is eligible for the vaccine can get it now – there’s no need to wait for further spread of the outbreak.

To stop the spread of the deadlier version of the virus, Congolese authorities said they have asked for 4 million doses, the Associated Press reported, but they haven’t gotten any. The WHO’s declaration is meant to spur other countries into donating vaccine doses and treatment medications.

Clade II mpox is still spreading in the U.S., the CDC says, but in small clusters. Case counts have remained stable at around 250 per month.

The Associated Press contributed to this report.