Research and analysis

Global high consequence infectious disease events: summary November 2023

Updated 25 April 2024

Interpreting this report

The report provides updates on known, high-consequence infectious disease (HCID) events around the world as monitored by the UK Health Security Agency’s (UKHSA) epidemic intelligence activities.

The report is divided into 2 sections covering all the defined HCID pathogens. The first section contains contact and airborne HCIDs that have been specified for the HCID programme by NHS England. The second section contains additional HCIDs that are important for situational awareness.

Each section contains information on known pathogens and includes descriptions of recent events. If an undiagnosed disease event occurs that could be interpreted as a potential HCID, a third section will be added to the report.

Events found during routine scanning activities that occur in endemic areas will briefly be noted in the report. Active surveillance, other than daily epidemic intelligence activities, of events in endemic areas will not be conducted (for example, actively searching government websites or other sources for data on case numbers).

The target audience for this report is any healthcare professional who may be involved in HCID identification, treatment and management.

Risk rating

Included for each disease is a current risk rating based on the probability of introduction to the UK and potential impact. Past UK experience and the global occurrence of travel-associated cases are also considered. Currently, all diseases are classified into one of 3 categories: Low, Very low and Exceptionally low/negligible.

Incidents of significance of primary HCIDs

Contact HCIDs

Crimean-Congo haemorrhagic fever (CCHF)

Geographical risk areas	Endemic in Africa, the Balkans, the Middle East and western and south-central Asia. Cases have also been reported in Russia and Georgia. Spain has previously reported locally acquired cases (first reported in 2016, with the latest case reported in 2022).
Sources and routes of infection	• bite from, or crushing of, an infected tick  • contact with the blood, tissues or body fluids of infected humans or animals
UK experience to date	Two cases have been reported in individuals who have travelled to the UK from Afghanistan in 2012 and Bulgaria in 2014
Risk rating	Low – rarely reported in travellers.
Recent cases or outbreaks	Between 1 January and 25 November 2023, the World Health Organization (WHO) reported 1,226 CCHF cases, including 114 deaths (case fatality rate (CFR) of 9.3%) from Afghanistan. In 2022, Afghanistan reported 286 suspected and 103 confirmed CCHF cases, including 15 deaths. On 29 November 2023, media reported that there had been 19 CCHF cases and 4 deaths reported from Diyala, Iraq, in 2023. On 8 November 2023, media reported there had been 73 confirmed CCHF cases and 20 deaths throughout Balochistan Province in Pakistan.

Ebola virus disease (EVD)

Geographical risk areas	Map of countries which have reported EVD cases up to January 2023.
Sources and routes of infection	• contact with blood, tissues or body fluids of infected animals, or consumption of raw or undercooked infected animal tissue • contact with infected human blood or body fluids
UK experience to date	Four confirmed cases (one lab-acquired in the UK in 1976, 3 healthcare workers associated with West African epidemic 2014 to 2015).
Risk rating	Very low – other than during the West Africa outbreak, exported cases are extremely rare.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Lassa fever

Geographical risk areas	Endemic in sub-Saharan West Africa.
Sources and routes of infection	• contact with excreta, or materials contaminated with excreta from an infected rodent  • inhalation of aerosols of excreta from an infected rodent  • contact with infected human blood or body fluids
UK experience to date	Three travel-related Lassa fever cases reported in 2022. Prior to this, 13 imported Lassa fever cases had been reported since 1971, all in travellers from West Africa.
Risk rating	Low – overall, Lassa fever is the most common imported viral haemorrhagic fever (VHF) but importations to the UK are still rare.
Recent cases or outbreaks	Between 1 January and 26 November 2023, Nigeria reported 8,423 suspected, 9 probable and 1,154 confirmed Lassa fever cases. Confirmed cases were reported from 28 states. Among confirmed cases, 197 deaths have been reported (CFR of 17.1%). The number of reported cases and deaths in 2023 are higher compared to the equivalent period in 2022 (7,591 suspected, 993 confirmed cases, including 184 deaths among confirmed cases), although the CFR remains lower (18.5% in 2022).

Marburg virus disease (MVD)

Geographical risk areas	Sporadic outbreaks have previously been reported in Central and Eastern Africa. A human case of MVD was reported in August 2021 in Guinea; this was the first case to be identified in West Africa. MVD cases were reported in Ghana for the first time in July 2022. MVD outbreaks were reported for the first time in Equatorial Guinea in February 2023 and in Tanzania in March 2023.
Sources and routes of infection	• exposure in mines or caves inhabited by Rousettus bat colonies • contact with infected human blood or body fluids
UK experience to date	No reported cases in the UK.
Risk rating	Very low – globally, 5 travel-related exported MVD cases have previously been reported in the literature.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Airborne HCIDs

Avian influenza A(H7N9) virus

Geographical risk areas	All reported human infections have been acquired in China.
Sources and routes of infection	• close contact with infected birds or their environments  • close contact with infected humans (no sustained human-to-human transmission)
UK experience to date	No known cases in the UK.
Risk rating	Very low (UKHSA risk assessment).
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Avian influenza A(H5N1) virus

Geographical risk areas	Human cases have been predominantly reported in South East Asia, but also in Egypt, Iraq, Pakistan, Turkey and Nigeria. Human cases (clade 2.3.4.4b) were reported in Spain and the USA in 2022, and in the UK in 2022 and 2023. The first human cases of avian influenza A(H5N1) (clade 2.3.4.4b) were reported from South America in 2023, from Ecuador and Chile.
Sources and routes of infection	• close contact with infected birds or their environments • close contact with infected humans (no sustained human-to-human transmission)
UK experience to date	As of September 2023, 5 detections were reported in the UK, one in 2022 and 4 in 2023.
Risk rating	Very low (UKHSA risk assessment).
Recent cases or outbreaks	In November 2023, the Cambodian Ministry of Health reported 2 confirmed cases of avian influenza A(H5N1), including one death, in a village in Kampot Province. The first case was a 21 year old female, with a symptom onset of 19 November 2023 (fever, shortness of breath and cough). She was admitted to hospital on 23 November 2023 where she subsequently died. The second case, a 4 year old female, was identified during contact tracing of the first case. She developed symptoms on 23 November 2023 and began receiving intensive care at Kampot Provincial Hospital on 25 November 2023. Both cases had exposure to sick or deceased poultry prior to symptom onset. There have been 6 human cases (including 4 deaths) of avian influenza A(H5N1) reported in Cambodia in 2023. Since 2005, Cambodia has reported 62 human cases of avian influenza A(H5N1) infection, including 41 deaths.

Middle East respiratory syndrome (MERS-CoV)

Geographical risk areas	The Arabian Peninsula – Yemen, Qatar, Oman, Bahrain, Kuwait, Saudi Arabia and United Arab Emirates.
Sources and routes of infection	• airborne particles • direct contact with contaminated environment  • direct contact with camels or consumption of raw camel milk
UK experience to date	Five MERS-CoV cases in total – 3 imported cases (2012, 2013 and 2018), 2 secondary cases in close family members of the case in 2013, 3 deaths.
Risk rating	Very low (UKHSA risk assessment).
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Mpox (Clade I only)

Geographical risk areas	Central Africa including, Central African Republic, Cameroon, the Democratic Republic of the Congo (DRC), Gabon and Republic of the Congo.
Sources and routes of infection	• close contact with an infected animal (in an endemic country) or an infected person • contact with clothing or linens (such as bedding or towels) used by an infected person • direct contact with mpox skin lesions or scabs • coughing or sneezing of an individual with an mpox rash • consumption of contaminated bushmeat
UK experience to date	In June 2022, the Advisory Committee on Dangerous Pathogens (ACDP) recommended that the strain of monkeypox virus (MPXV) largely responsible for the global outbreak (Clade IIb, B.1 lineage) should no longer be classified as an HCID. In January 2023, the ACDP recommended that all Clade II MPXV should no longer be classified as an HCID. No cases of Clade I mpox have been reported in the UK. Between 2018 and 2021, 7 cases of mpox were identified in the UK which would no longer be classified as HCID mpox, but were treated as HCID cases at the time: 4 of the cases were imported from Nigeria, 2 cases were household contacts and one case was a healthcare worker involved in the care of an imported case.
Risk rating	Very low – no known importations of Clade I mpox into the UK.
Recent cases or outbreaks	Sequencing data is rarely available for mpox cases reported from endemic African countries where clade I MPXV is known to circulate. Between 1 January and 12 November 2023, a total of 12,569 suspected mpox cases, including 581 mpox deaths (CFR of 4.6%), were reported in 156 health zones from 22 out of 26 provinces in the Democratic Republic of the Congo (DRC). On 24 November 2023, the WHO reported evidence of sexually transmitted Clade I MPXV for the first time. The first known cases were reported when a man, resident in Belgium and with connections to the DRC, tested positive for Clade I MPXV in Kenge, Kwango Province, during a visit to the DRC. Among 27 contacts identified, 5 sexual contacts tested positive for Clade I MPXV, with closely related viral sequences. Despite the patient having no reported exposure to another person with confirmed mpox, epidemiological investigations concluded that exposure to mpox most likely occurred in Belgium.

Nipah virus

Geographical risk areas	South East Asia, predominantly in Bangladesh and India. Cases have also been reported in Malaysia and Singapore.
Sources and routes of infection	• direct or indirect exposure to infected bats • consumption of contaminated raw date palm sap • close contact with infected pigs or humans
UK experience to date	No known cases in the UK.
Risk rating	Exceptionally low/negligible – no travel-related infections in the literature.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Pneumonic plague (Yersinia pestis)

Geographical risk areas	Predominantly sub-Saharan Africa but also Asia, North Africa, South America, Western USA. Endemic in Madagascar, Peru, and the DRC.
Sources and routes of infection	• flea bites  • close contact with infected animals  • close contact with human cases of pneumonic plague
UK experience to date	Last outbreak in the UK was in 1918.
Risk rating	Exceptionally low/negligible
Recent cases or outbreaks	In Madagascar, on 18 November 2023, media reported 11 suspected cases of pneumonic plague, including 8 deaths, from the villages of Ankazomanga (4 suspected fatal cases) and Voagnana (7 suspected cases; 4 deaths) in the Atsimo-Atsinanana Region.

Severe acute respiratory syndrome (SARS)

Geographical risk areas	Currently none. Two historical outbreaks originating from China in 2002 and 2004.
Sources and routes of infection	• airborne particles  • direct contact with contaminated environment
UK experience to date	Four imported SARS cases related to the 2002 outbreak.
Risk rating	Exceptionally low/negligible
Recent cases or outbreaks	No confirmed or suspected human cases reported globally since 2004.

Incidents of significance of additional HCIDs

Argentine haemorrhagic fever (Junin virus)

Geographical risk areas	Argentina (central). Endemic to the provinces of Buenos Aires, Córdoba, Santa Fe and La Pampa.
Sources and routes of infection	• direct contact with infected rodents  • inhalation of infectious rodent fluids and excreta  • person-to-person transmission has been documented
UK experience to date	No known cases in the UK.
Risk rating	Exceptionally low/negligible – one travel-related case was identified in Belgium in 2020.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Bolivian haemorrhagic fever (Machupo virus)

Geographical risk areas	Bolivia – cases have been identified in the departments of Beni (Mamoré, Iténez and Yucuma provinces) and Cochabamba (Cercado province).
Sources and routes of infection	• direct contact with infected rodents  • inhalation of infectious rodent fluids and excreta  • person-to-person transmission has been documented
UK experience to date	No known cases in the UK.
Risk rating	Exceptionally low/negligible – travel-related cases have never been reported.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Lujo virus disease

Geographical risk areas	A single case acquired in Zambia led to a cluster in South Africa in 2008.
Sources and routes of infection	• presumed rodent contact (excreta, or materials contaminated with excreta of infected rodent)  • person to person via body fluids
UK experience to date	No known cases in the UK.
Risk rating	Exceptionally low/negligible – a single travel-related case has been reported. No cases have been reported anywhere since 2008.
Recent cases or outbreaks	No confirmed or suspected human cases reported since 2008.

Severe fever with thrombocytopenia syndrome (SFTS)

Geographical risk areas	Mainly reported from China (south-eastern), Japan and Korea. Cases have also been reported in Taiwan, Thailand, Myanmar and Vietnam. Serological evidence of SFTS in Pakistan.
Sources and routes of infection	• presumed to be tick exposure  • person-to-person transmission described in household and hospital contacts, via contact with blood or bloodstained body fluids
UK experience to date	No known cases in the UK.
Risk rating	Exceptionally low/negligible – not known to have occurred in travellers.
Recent cases or outbreaks	Between week 1 and 45 (up to 12 November) of 2023, the Korean Disease Control and Prevention Agency reported 195 SFTS cases, including 37 associated deaths. This is comparable to the equivalent 2022 period (188 cases including 33 deaths). The Gyeonggi Region reported the most cases (31 cases), followed by Gangwon (28 cases). On 21 November 2023, media reported a confirmed case of SFTS in a woman in Zhejiang Province, China. Haemaphysalis longicornis, a principal tick vector of SFTS virus, is widely distributed in areas of high SFTS incidence in China. The first human cases of SFTS were reported in northeast and central China in 2009.

Andes virus (Hantavirus)

Geographical risk areas	Chile and southern Argentina.
Sources and routes of infection	• rodent contact (excreta, or materials contaminated with excreta from an infected rodent)  • person-to-person transmission described in household and hospital contacts
UK experience to date	No known cases in the UK.
Risk rating	Very low – rare cases in travellers have been reported.
Recent cases or outbreaks	On 3 November 2023, media reported that there had been 19 hantavirus cases in Salta Province, Argentina, in 2023. On 2 November 2023, media reported 15 cases of hantavirus in Hipolito Irigoyen, Misiones Province, in 2023. Although the type of hantavirus was not specified in either report, cases of Andes hantavirus had previously been detected in both provinces. On 13 November 2023, media reported a fatal confirmed case of hantavirus in a 34-year-old male in the Metropolitan Region of Chile. The case had exposure to mouse excrement, developed symptoms on 6 November 2023 and was admitted to hospital on 10 November 2023, where he subsequently died. The type of hantavirus was not specified.

Avian influenza A(H5N6) virus

Geographical risk areas	Mostly China. New strain reported in Greece in March 2017, and subsequently found in Western Europe in birds.
Sources and routes of infection	Close contact with infected birds or their environments.
UK experience to date	No known cases in the UK.
Risk rating	Very low – not known to have occurred in travellers (UKHSA risk assessment).
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Avian influenza A(H7N7) virus

Geographical risk areas	Sporadic occurrence in birds across mainland Europe and the UK. A human case was reported in Ireland in 1996, 89 cases were reported in the Netherlands in 2003, and 3 human cases were reported in Italy in 2013.
Sources and routes of infection	• close contact with infected birds or their environments  • close contact with infected humans (no sustained human-to-human transmission reported)
UK experience to date	No known cases in the UK.
Risk rating	Very low – human cases are rare, and severe disease even rarer.
Recent cases or outbreaks	No confirmed or suspected human cases were reported in November 2023.

Authors of this report

Emerging Infections and Zoonoses Team, UKHSA