The 3,135 cases came from 42 countries, and included 12 deaths, WHO said. Between January and September, a total of 44,299 confirmed cases have been reported from 93 nations, including 180 deaths.
"Since the last edition of this report, Malaysia, Namibia, the Netherlands, Portugal, and Spain have reported detection of clade Ib monkeypox virus (MPXV) for the first time," the report said.
"New imported cases of mpox due to clade Ib MPXV detected among travellers have been reported in Belgium, Canada, Germany, Italy, Qatar, and Spain."
The WHO report highlighted that six nations outside of Central and East Africa -- the United States, Italy, Malaysia, the Netherlands, Portugal, and Spain -- have reported clade Ib monkeypox cases among people with no travel links, suggesting the virus strain is circulating locally.
"In addition to countries in Africa, these countries are now also classified as experiencing community transmission of clade Ib MPXV," the report said.
As for overall monkeypox cases globally, Africa reported 84 percent of the 3,135 confirmed cases in September, according to the WHO.
Southeast Asia and Europe reported an increase in confirmed cases in September compared to August, the organization said.
In contrast, the Americas and the Eastern Mediterranean, African, and Western Pacific regions reported a decrease in cases.
Six clade I monkeypox cases have been reported nationwide among people who recently traveled to regions associated with the outbreak in Central and Eastern Africa, the CDC said.
The agency clarified that it does not see any major risk posed by clade I monkeypox to the United States.
"CDC regularly assesses the risk to the overall population and specific populations within the United States posed by the clade I monkeypox outbreak; it remains low," the agency said.
During the incubation period, which typically runs for 3-17 days, an infected person may not display any symptoms and could even feel fine, the agency said.
Individuals who are at most risk of severe monkeypox disease include those with weakened immune systems, pregnant women, children younger than one year, and people who have a history of eczema.
In a statement, Assistant State Public Health Officer Rita Nguyen urged Californians to stay informed and take preventive measures to address the situation, particularly individuals who are more susceptible to exposure to monkeypox.
"Clade I mpox cases can be severe. Risk of severe disease and hospitalization are highest for people with weakened immune systems, so it's critical to protect yourself by getting both doses of the mpox vaccine if you or your sex partner(s) may be at risk for mpox," she said.