Mpox Outbreak

Authored by
Staff
Last reviewed
March 12, 2024
Content Overview
Mpox outbreaks in 2024 include Africa, the Americas, China, Europe

Mpox Outbreaks 2024

The World Health Organization (WHO) Mpox External Situation Report #31 confirmed on December 22, 2023, that it has received mpox case reports from 115 affected countries since May 2022. The WHO Director-General declared a public health emergency of international concern (PHEIC) regarding outbreaks on July 23, 2022. The WHO announced the PHEIC ended on May 11, 2023. This global outbreak (93,497 cases) was caused by mpox clade II and occurred in 118 locations.

Mpox Virus Cades

The natural reservoir of the zoonotic mpox virus (MPXV) remains unknown. There are two MPXV clades: clade I, previously known as the Congo Basin clade, and clade II, formerly the West African clade; clade II further has two subclades: clade IIa and clade IIb. Since May 2022, an epidemic of clade IIb MPXV was initially detected in the Canary Islands and is ongoing globally in 2023. Clade I MPXV community outbreaks occur regularly in Cameroon, the Central African Republic, and the Democratic Republic of Congo (DRC). The European Centre for Disease Prevention and Control (ECDC) stated on December 5, 2023, that there's no evidence that clade 1 is spreading outside of central Africa. Before April 2023, no formally documented cases of sexual transmission of clade I MPXV were registered globally. 

Mpox Outbreak United States

In the U.S., initial mpox virus clade IIb cases were detected in Boston, MA, in May 2022. The U.S. government declared an outbreak in August 2022. As of March 2024, the U.S. Centers for Disease Control and Prevention (CDC) reported 32,063 confirmed cases of mpox and 58 deaths in the U.S. During 2023, there were 241 mpox cases confirmed by the CDC.

On January 31, 2023, the U.S. HHS did not renew the public health emergency declaration for mpox. The mpox public health emergency in San Francisco, CA, ended on October 27, 2022, followed by New York in November 2022. 

The ACIP presentation on October 25, 2023, reviewed mpox infections in Chicago, indicating an increase in mpox (18), particularly among previously JYNNEOS vaccinated persons. And in a CDC Morbidity and Mortality Weekly Report published on September 1, 2023, among 38 (73%) patients with no known exposure to a person with mpox, behaviors preceding illness included sexual activity (17; 45%), close face-to-face contact (14; 37%), attending large social gatherings (11; 29%), and being in occupational settings (10; 26%). The CDC published a Dispatch, Volume 29, Number 10—October 2023, confirming that 1.3% of reported mpox instances were in children and adolescents <18 years of age. The U.S. CDC Advisory Committee on Immunization Practices (ACIP) presented various mpox data on June 23, 2023. 

The Lancet reported on August 4, 2023, that sexually transmitted coinfections (STI) were prevalent in mpox patients, including gonorrhea (28%), chlamydia (25%), syphilis (8%), and HIV (38%).

Mpox Africa

The WHO reports that mpox is an infectious disease endemic in densely forested West, Central, and East Africa regions. The first human case of Mpox was identified in the Democratic Republic of Congo (DRC) in 1970. During 2016–2022, PCR testing confirmed 100 mpox cases among 302 suspected cases in the Central African Republic

A novel mpox outbreak in eastern DRC confirmed mpox infections caused symptoms in a wide age range of participants, including children, with most clade 1 cases presenting in sexually active heterosexual individuals.

In December 2023, the U.S. CDC issued a Health Alert Network Health Advisory to notify clinicians and health departments about the occurrence, geographic spread, and sexually associated human-to-human transmission of Clade I MPXV in the DRC. The CDC also issued Level 2 travel advisory in February 2024 to alert international travelers regarding mpox outbreaks in African countries. In March 2024, researchers reported 21,630 suspected MPXV Clade 1 cases and 1,003 deaths. Around 85% of the deaths recorded during this period were children under 15 years of age.

Mpox Europe

The European Centre for Disease Prevention and Control (ECDC) and WHO published a statement confirming that 26,703 mpox cases were identified from May 2022 to January 14, 2024, from 45 countries and areas throughout the European Region. Over the past four weeks, 138 cases of mpox have been identified from 11 countries and areas in Europe.

Mpox Pacific Region

China's National Health Commission (NHC) confirmed in a statement in September 2023 that it plans to manage mpox, Category B protocols, similar to other infectious diseases such as COVID-19, HIV, and rabies, after detecting 501 cases of viral infection in August 2023. These reported cases have been identified as clade IIb MPXV. The WHO situation report #27, published on August 14, 2023, identified sustained community transmission of mpox in China. Mpox cases increased to 491 on the Chinese mainland in July 2023, according to China's Center for Disease Control and Prevention (China CDC). That was an increase from 106 cases in June 2023. Since June 23, 2022, China has listed mpox as a second-class legal infectious disease. The WHO reported 106 mpox cases in Beijing in July 2023, plus recent infections in Taiwan and Hong Kong. The Hong Kong Special Administrative Region of the People's Republic of China recently recorded its fifth Mpox patient since September 2022. The Taiwan Centers for Disease Control and Prevention reported that 266 cases (250 local and 16 imported cases) have been diagnosed in Taiwan. As of August 7, a total of 77,809 mpox vaccination services have been completed in China.

A U.S. CDC study reported in July 2023 that asymptomatic mpox infections were likely underestimated in Japan and were comparable in magnitude to symptomatic infections. Japan's Ministry of Health, Labor and Welfare Health reported 169 mpox cases as of May 28, 2023, since the first domestic case in July 2022. On March 20, 2023, the Japanese Ministry of Health reported 13 men were confirmed to have a mpox infection. The Western Pacific Region reported additional mpox cases in early April 2023, driven by an outbreak of mpox affecting mainly men in Japan. 

The Korean Herald reported that Korea's Centers for Disease Control and Prevention announced in April 2023 that it would raise the crisis alert level from 'Level 1' to 'Level 2 caution' following a mpox outbreak of about sixty cases.

Mpox United Kingdom

The U.K. Health Services Agency (UKHSA) began reporting mpox cases in March 2022, which accelerated in May 2022. The first smallpox specimen was identified during this outbreak through retrospective testing in the United Kingdom on March 7, 2022. In 2023 and up to March 2024, there have been a total of 160 cases of mpox reported in the UK. Of these, 153 were in England (68 cases were presumed to have acquired mpox in the UK, 58 were acquired outside the UK, and 27 are awaiting classification). The UKHSA published that the mpox clade of monkeypox predominantly circulating in the U.K. (Clade IIb, B.1 lineage) was no longer classified as a High Consequence of Infectious Disease. Before the recent outbreak, between 2018 and 2021, there were seven cases of mpox in the U.K. Of these; four were imported. There was no documented community transmission in previous outbreaks.

Mpox in Women

Eurosurveillance published a study on December 1, 2022, on mpox infections in 158 women. In Spain, 7,393 confirmed cases of Mpox, 2.1% of cases (158) have been in women diagnosed between April 26 and November 21, 2022. The average age of female patients was 34 years, and two were pregnant at the time of mpox infection. The most likely transmission mechanism was close contact during sexual relationships. 

Mpox and HIV

People with HIV and mpox were not at an increased risk for hospitalization unless they were immunosuppressed, according to an abstract presented at the International AIDS Society Conference on HIV Science in July 2023.

Mpox Disease

The mpox virus, a member of the Orthopoxvirus genus in the family Poxviridae, causes mpox. The mpox virus has identified two distinct genetic clades of the Congo Basin and the West African clades. According to the WHO, the mpox virus is transmitted from one person to another by contact with lesions, body fluids, respiratory droplets, and contaminated material. A meta-study published in the Archives of Virology on June 29, 2023, found that the median mpox incubation period is seven days, and immunocompromised people with HIV comprise about 36% of documented cases.

Mpox Vaccines and Treatments

Various mpox vaccines (JYNNEOS®) and treatments (TPOXX) are authorized in 2023. Numerous research studies have clinically reviewed the mpox outbreak as of September 2023.