Mpox Outbreak 2023

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Last reviewed
September 20, 2023
Content Overview
Mpox outbreaks in 2023 include Africa, the Americas, Chicago, China, Denver, France, Japan, London, New York, Portugal, South Korea, Spain, Taiwan.

Mpox Outbreaks

The World Health Organization (WHO) External Situation Report #28 confirmed that since August 14, 2023, up until September 11, 2023, it has received reports of 1,131 new confirmed cases of mpox, five new related deaths, and 22 of the 115 affected countries have reported new cases within the last 21 days. Sustained community transmission continues to be observed mainly in the South-East Asia and Western Pacific regions. While mpox continues to pose a public health risk among certain populations after the termination of the public health emergency of international concern in May 2023, the WHO assesses the global mpox risk as Moderate. Since WHO recommends the control and elimination of mpox human-to-human transmission as appropriate, countries' preparedness and response actions can now be guided by the standing recommendations issued by the WHO Director-General in August 2023.

As of August 11, 2023, the European Centre for Disease Prevention and Control (ECDC) reported the ten most affected countries since May 2022 are the United States of America (n = 30,446), Brazil (n = 10,967), Spain (n = 7,560), France (n = 4,150), Colombia (n = 4,090), Mexico (n = 4,045), Peru (n = 3,812), The United Kingdom (n = 3,771), Germany (n = 3,694), and Canada (n = 1,496). These countries represent about 83% of all mpox cases reported globally.

The first mpox specimen was identified during this outbreak through retrospective testing in the United Kingdom on March 7, 2022. The earliest date of mpox symptom onset in the U.K. was reported as April 17, 2022. The global outbreak accelerated in May 2022. Since then, about 113 countries have reported over 89,000 laboratory-confirmed mpox cases, including 152 related fatalities. The WHO Director-General declared a Public Health Emergency of International Concern (PHEIC) regarding mpox virus (MPXV) outbreaks on July 23, 2022. The WHO announced the PHEIC ended on May 11, 2023.

Recent mpox outbreaks have been identified in BelgiumChicago (U.S.), ChinaDenver (U.S.), Jerusalem, Israel, the Netherlands, New York (U.S.),   ParaguayParis (France), Seoul (South Korea), SpainTokyo (Japan), Thailand, Taiwan, and the United Kingdom (London).

Mpox United States 2023

In the U.S., initial mpox cases were detected in Boston, MA, in May 2022, and the government declared an outbreak in August 2022. On October 27, 2022, the Mpox public health emergency in San Francisco, CA, ended, followed by New York in November 2022. And on January 31, 2023, the U.S. HHS did not renew the public health emergency declaration for mpox. On June 20, 2023, NYSDOH Commissioner James McDonald posted a Mpox Update video.

The U.S. Centers for Disease Control and Prevention (CDC) published a Dispatch, Volume 29, Number 10—October 2023, confirming 1.3% of reported mpox cases were in children and adolescents <18 years of age. The analysis of global surveillance data showed one hospital intensive care unit admission and 0 deaths in that age group. 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 Lancet reported on August 4, 2023, sexually transmitted coinfections were prevalent (STI) in mpox patients, including gonorrhea (28%), chlamydia (25%), syphilis (8%), and HIV (38%).

The U.S. CDC Advisory Committee on Immunization Practices (ACIP) presented various mpox outbreak data on June 23, 2023. It published Notes from the Field: Emergence of a Mpox Cluster Primarily Affecting Persons Previously Vaccinated Against Mpox — Chicago, Illinois, March 18–June 12, 2023.

The CDC MMWR Domestic Mpox Response — United States, 2022–2023, published on May 19, 2023, disclosed Black and Hispanic persons represented 33% and 31% of cases, respectively; 87% of 42 fatal cases occurred in Black persons. The CDC's Clinician Outreach and Communication Activity (COCA) call on May 18, 2023, presented Mpox Update: Stay Up to Date on Testing, Treatment, and Vaccination. Furthermore, the CDC issued a Health Update on May 15, 2023, regarding Mpox vaccination breakthrough cases, and the CDC disclosed Mpox wastewater detections and Non-Variola Orthopoxvirus Laboratory Testing as of May 2023.

As of July 28, 2023, the CDC reported over 30,600 mpox cases and 45 related fatalities since May 2022. Chicago, Illinois, reported 46 mpox cases; and New York City confirmed on June 15, 2023, 51 people tested positive for mpox in 2023; Denver  Public Health reported four mpox cases (2 breakthrough cases) on June 26, 2023; the New Jersey Department of Health reported two new mpox cases on June 2, 2023.

A study based on California data published on August 9, 2023, concluded while participants' assessment of symptoms in partners may be imperfect, these findings suggest individuals without visibly prominent mpox symptoms transmit infection.

Mpox Africa

The first human case of Mpox was identified in the Democratic Republic of Congo in 1970. The WHO agreed that Clade II consists of 2 subclades, Clade IIa and Clade IIb. Each of the clades and subclades is subdivided into multiple lineages. During 2016–2022, PCR testing confirmed 100 mpox cases among 302 suspected cases in the Central African RepublicAfrica's CDC confirmed since the beginning of 2022, and as of July 25, 2022, a total of 2,031 cases (250 confirmed; 1,781 suspected) and 75 deaths (CFR: 3.7%) of mpox by nine endemic and two non-endemic countries. Only the Central African Republic, the DRC, Ghana, Liberia, and Nigeria countries have reported mpox cases in 2023. The CDC issued Level 1 travel advisories in 2021 to alert international travelers regarding mpox outbreaks in African countries, such as Nigeria.

Mpox Europe

The European Centre for Disease Prevention and Control (ECDC) published a communicable disease threats report for week #27, indicating a mpox outbreak in Portugal as of early July 2023. The ECDC published a report on public health considerations for mpox in EU/EEA countries in 2023. In addition, a study published by the International Journal of Infectious Diseases on May 15, 2023, shows considerably more mpox DNA in wastewater samples than expected based on hospitalization data, suggesting the mpox outbreak was underestimated in central Europe. Public Health France reported 17 confirmed mpox cases in the Centre-Val de Loire region in April 2023. According to researchers from Portugal's National Institute of Health, a genomic and epidemiologic analysis of the 2022 mpox outbreak estimates that 1.3% of MSM in Portugal were infected with the virus. According to the Carlos III Health Institute, six cases of mpox were diagnosed in Spain in May 2023, 56 since the beginning of 2023, and 7,555 since the mpox outbreak began in May 2022. The Vall d'Hebron (Barcelona, vaccinated against smallpox in childhood) and Ramón y Cajal (Madrid) hospitals diagnosed two patients in May 2023 who had already had the infection before.

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 cases 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 as having 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 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 U.K.

The U.K. Health Services Agency (UKHSA) began reporting mpox cases in March 2022, which accelerated in May 2022. Through December 2022, 3,732 confirmed and highly probable mpox cases were reported in the U.K. Of these, 3,553 were in England. In 2023 (up to 31 July 2023), a further 39 cases of mpox were reported in the U.K. Of these, 38 were in England. On June 16, 2023, the UKHSA announced that mpox vaccinations would remain available in London. 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 Nov 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.