Research and analysis

Infectious disease surveillance and monitoring for animal and human health: summary May 2024

Updated 1 August 2024

Interpreting this report

The UK Health Security Agency’s (UKHSA) Emerging Infections and Zoonoses (EIZ) team uses an integrated horizon scanning approach, which combines information on both human and animal health, to identify and assess outbreaks and incidents of new and emerging infectious diseases globally. For further information about the EIZ team’s horizon scanning process, please see our Epidemic intelligence activities.

This summary provides an overview of incidents (new and updated) of public health significance, which are under close monitoring. The incidents are divided into 2 sections: Notable incidents of public health significance and Other incidents of interest. For each notable incident of public health significance, an incident assessment is provided, based on the EIZ team’s interpretation of the available information.

The report also includes a section that focuses on Novel pathogens and diseases and a final Publications of interest section, which contains new publications relevant to emerging infections.

Epidemiological updates for diseases classified as a high consequence infectious disease (HCID) are published in UKHSA’s HCID monthly summary, unless they are considered a notable incident of public health significance, in which case a more detailed summary will be provided in this report.

For more information, or to sign up to the distribution list to receive an email alert when new reports are published, please contact epiintel@ukhsa.gov.uk

Notable incidents of public health significance

Summary of incidents

Disease or infection	Location	New or update since the last report
Avian influenza A(H5N1)	United States	Update
Oropouche fever	Cuba	New

Avian influenza A(H5N1) – United States

Event summary

In May 2024, the United States Centres for Disease Control and Prevention (US CDC) reported 2 confirmed human cases of avian influenza A(H5N1) in Michigan state, United States of America. The cases were not epidemiologically linked but were both dairy farm workers with exposure to infected dairy cattle. This brings the total number of human cases associated with this ongoing avian influenza A(H5N1) in dairy cattle to 3.

The first of these new cases (reported on 22 May 2024) was a dairy worker being actively monitored following occupational exposure to dairy cattle infected with avian influenza A(H5N1). The case reported mild symptoms to health officials, notably conjunctivitis. Nasal and conjunctival specimens were collected for testing, with the former returning a negative test result for influenza virus at a state health laboratory. Both samples were sent to the US CDC for testing, which confirmed a negative result for the nasal specimen, whilst the conjunctival specimen tested positive for avian influenza A(H5). Subsequent sequencing confirmed infection with avian influenza A(H5N1) clade 2.3.4.4b genotype B3.13; which was closely related to viruses detected in dairy cattle and a previous human case reported in Texas state. The viral sequence lacked mutations which would infer improved affinity and transmissibility amongst humans but did contain a PB2 M631L mutation which has been associated with enhanced viral replication and disease severity in animal models. No markers for antiviral resistance were observed, and the sequence was similar to existing avian influenza A(H5N1) candidate vaccine viral sequences shared with manufacturers for potential vaccine development.

The second new case (reported on 30 May 2024) was also a dairy worker who had exposure to dairy cattle infected with avian influenza A(H5N1). The case reported upper respiratory tract symptoms (cough) in addition to watery discharge from the eyes. The case was treated with antivirals (oseltamivir). Household contacts were monitored, and whilst none developed symptoms, antivirals were offered as post-exposure prophylaxis. Other workers on the same farm did not report symptoms whilst being actively monitored. A nasopharyngeal swab specimen tested positive for avian influenza A(H5) at a state health laboratory. Whilst the specimen was unable to be fully sequenced, US CDC confirmed avian influenza A(H5N1) clade 2.3.4.4b infection; with the isolate closely related to those currently circulating in dairy cattle.

During May 2024, the United States Department of Agriculture (USDA) reported avian influenza A(H5N1) detections in 44 dairy cattle herds across 9 states in the US including, Michigan (n=18), Idaho (n=15), South Dakota (n=4), Colorado (n=3), Texas (n=4). By the end of May 2024, 80 affected herds had been reported since the outbreak began (Figure 1). In addition to new detections in dairy cattle, the USDA also reported detections in an alpaca herd (with exposure to infected poultry recently depopulated on the premises), in house mice (in New Mexico state), and in domestic cats; some linked to affected dairy farms. The US National Veterinary Services Laboratories reported that virus sequenced from the alpacas were the B3.13 genotype and identical viruses from infected birds recently depopulated on the premises and those currently circulating in dairy cattle.

Incident assessment

These cases represent the third and fourth human cases of avian influenza A(H5N1) reported in the US, with the first case reported in 2022. Globally, between January 2003 to 1 June 2024, 893 cases of human infection with avian influenza A(H5N1) virus and 463 deaths (case fatality rate (CFR) of 52%) were reported from 25 countries. Whenever avian influenza viruses are circulating in animals, there is a potential risk of sporadic human cases following exposure to infected animals or their contaminated environments. Human cases of avian influenza A(H5) are rare and there is limited evidence of human-to-human transmission of these viruses. The WHO has published interim genetic and antigenic characteristics of clade 2.3.4.4b avian influenza A(H5N1) virus summarising the genetic sequencing of an earlier human case in Texas state, US. 

The Department for Environment, Food and Rural Affairs and the Animal and Plant Health Agency assess the risk of avian influenza A(H5N1) in livestock in Great Britain (GB) as very low. As avian influenza A(H5N1) clade 2.3.4.4b genotype B3.13 has not been detected in GB, the zoonotic transmission risk to people in contact with infected animals in the UK is also considered very low. Currently, there are no indicators of increasing risk to human health. The Food Standards Agency assess the risk of avian influenza A(H5N1) clade 2.3.4.4b genotype B3.13 infectious exposure to UK consumers, through imported US dairy products, to be very low.

Since 2021, 5 human cases of avian influenza A(H5N1) clade 2.3.4.4b have been reported in the UK.  These cases were associated with poultry exposures and were either asymptomatic or had mild symptoms. For further information on avian influenza viruses, see the UKHSA’s avian influenza webpage.

Oropouche Fever – Cuba

Event summary

On 20 May 2024, Santiago de Cuba’s Provincial Health Directorate (login required) reported detections of a non-specific febrile illness in 8 human cases between 12 and 18 May 2024 from the Santiago de Cuba and Songo La Maya municipalities in Santiago de Cuba Province, Cuba. The cases developed symptoms including headache, fever, general malaise, loss of appetite and muscle pain, which subsided after approximately 4 days. On 27 May 2024, Cuba’s Ministry of Health (in Spanish) (MoH) reported that laboratory testing of samples from these cases confirmed OROV infection; the first ever detections of OROV reported in Cuba; the first ever detections of OROV in Cuba.

A total of 74 confirmed cases were reported between 2 and 23 May 2024: 54 cases from Province of Santiago de Cuba and 20 cases from Province of Cienfuegos. All cases recovered approximately 4 days following symptom onset.

Figure 1: Geographical areas in the Americas Region reporting cases of Oropouche virus during 2024.

Adapted from the US CDC Oropouche Fever in the Americas information page. Accessed: 3 July 2024.

Incident assessment

Oropouche fever is caused by OROV, which is known to circulate in the Caribbean, Central and South America. OROV is primarily transmitted to humans from the Culicoides paraensis midge but can also be transmitted by the Culex quinquefasciatus mosquito. Other than humans, vertebrate hosts include non-human primates, sloths and birds. Due to its mild, often self-limiting manifestation and similarity in clinical presentation to other arboviral infections circulating in the Americas Region (for example dengue, chikungunya and yellow fever), there is likely an underestimation of the true burden of OROV disease due to low case detection and/or misdiagnosis. There are currently no specific antiviral treatments or vaccines against OROV.

On 9 May 2024 (in Spanish), the WHO Pan American Health Organization (PAHO) issued an epidemiological alert for Oropouche fever in the Americas Region due to an increase in cases during 2024 (5,193 confirmed cases up to 9 May 2024) and reports of spread new geographic areas of OROV endemic countries including Brazil and Bolivia.

The WHO states that as this is the first detection of OROV in Cuba, there is a risk of additional case detection amongst a highly susceptible population.  The vectors of OROV are also found widely across the Americas Region and active outbreaks are ongoing in Brazil, Bolivia, Colombia and Peru. The WHO have also stated that there is a risk of Oropouche fever spreading internationally from Cuba as it is a popular tourist destination. Between May and January 2024, approximately 1.1 million tourists visited Cuba, including 33,000 UK travellers.

Whilst travel associated infections are possible in the UK in returnees from OROV affected areas, further transmission in the UK is unlikely due to the absence of established competent vectors required for OROV transmission. There is no evidence of human-to-human transmission of OROV. As of May 2024, the UK has not reported any Oropouche fever cases.

Other incidents of interest

Summary of other incidents

Disease or infection	Location
Cholera	Multi-country
Dengue)	Multi-country
Meningococcal disease	Multi-country
Measles	European Region
Hepatitis E	Chad
Parvovirus B19	European Region
Yellow fever	Multi-country
Polio	Multi-country

Cholera

During May 2024 (epidemiological weeks 18 to 21), 46,364 new cholera cases and 185 cholera associated deaths were reported from 19 countries and territories across 4 WHO regions. This is a 58% increase in cases and a 37% decrease in deaths compared to April 2024. Most cases were reported in the Eastern Mediterranean Region (33,779 cases and 54 deaths across 6 countries) followed by the African Region (12,504 cases and 130 deaths across 11 countries).

On 5 May 2024 (login required), Kenya issued a public health advisory for cholera and waterborne diseases due to heavy rainfall and widespread flooding affecting multiple parts of the country. Over 316,000 people are thought to have been displaced with 284 displacement camps across Kenya. Health and sanitation facilities have been disrupted including access to clean water. By the end of May 2024, the Kenyan Ministry of Health has recorded 157 suspected and 8 confirmed cases of cholera. 

Cholera outbreaks in Comoros and Mayotte remain ongoing. Comoros has recorded 7,945 cholera cases and 125 associated deaths (login required) (CFR of 1.6%) since 1 January 2024. Most cases are concentrated on the Island of Ndzuwani (6,855 cases and 104 deaths). During May 2024, 4,412 new cases and 54 deaths were reported, representing a 180% increase in cases and 108% increase in deaths compared to April 2024. Mayotte has recorded 125 cholera cases and 2 associated deaths (CFR of 1.6%) since the start of its outbreak on 18 March 2024.

On 16 May 2024, the WHO reported the global stockpile of oral cholera vaccine (OCV) has been partially replenished (3.2 million doses). Global demand continues to outweigh supply:82 million OCV doses have been requested by affected countries but only 46 million doses have been produced in the same time. Therefore, preventative vaccination campaigns remain suspended in order to prioritise doses for severe outbreaks. As of May 2024, the WHO maintains cholera as a grade 3 emergency and assesses the risk at the global level as very high.

Dengue

Between 1 January and 31 May 2024, the Africa Centres for Disease Control and Prevention (Africa CDC) reported 41,765 dengue cases (9,185 confirmed cases) and 59 deaths across 10 African Union Member States. Most cases have been reported from Burkina Faso (24,911 cases, 45 deaths), Mauritius (8,491 cases, 8 deaths) and Sudan (1,830 cases, 2 deaths).

In the Americas Region, the PAHO reported 9,215,0861 dengue cases and 4,476 deaths between 1 January and 26 May 2024. This represents a 231% increase in cases compared to the same time period in 2023, and a 424% increase compared to the previous 5-year average. Most cases reported during week 21 of 2024 were from Brazil (181,170 cases), Argentina (10,056 cases) and Colombia (9,961 cases).

The WHO published a Disease Outbreak News on 30 May 2024 due to a substantial increase in dengue cases reported globally, particularly in the Americas Region. Over 90 countries have recorded active dengue transmission. Many endemic countries have suboptimal case detection and reporting mechanisms, so the true number of dengue cases is likely underestimated. With over 9 million dengue cases reported in the WHO Americas Region by the end of May 2024, this has far exceeded total case numbers for 2023 (in Spanish) (4.6 million cases); attributed to changes in the geographical distribution and abundance of dengue vectors (Aedes aegypti and Aedes albopictus), climate change and weather phenomena that favour vector reproduction, and changes in circulating dengue serotypes.

In Europe, the European Centre for Disease Prevention and Control (ECDC) has not reported any locally acquired cases of dengue within mainland Europe so far in 2024. Autochthonous transmission of dengue typically occurs between June and November. In May 2024, France recorded 601 imported cases of dengue (in French); 60% of these cases were in travellers from Guadeloupe and Martinique. Case numbers in Guadeloupe and Martinique have declined during May 2024.

Meningococcal disease

On 17 May 2024, the ECDC reported 12 cases of meningococcal disease in pilgrims returning from the Kingdom of Saudi Arabia. Cases were reported from France (4 cases), the UK (3 cases) and the US (5 cases). 6 of these cases were genetically related. Over 1.5 million travellers are expected to visit the Kingdom of Saudi Arabia during the Hajj pilgrimage period (14 to 19 June 2024). The ECDC and US CDC have issued guidance around vaccination and continue monitoring returning Umrah pilgrims ahead of the Hajj pilgrimage period. Vaccination with the quadrivalent meningococcal vaccine is required as part of the Hajj pilgrimage visa application. Post-exposure prophylaxis with antibiotics is recommended by the US CDC after contact with a confirmed case, regardless of immunisation status.

Measles

In May 2024, the ECDC and WHO issued health warnings regarding the resurgence of measles cases in Europe during 2024. ECDC has reported 672 cases of measles across 18 Eurpoean Union (EU) and European Economic Area (EEA) member states in May 2024. Most cases were reported from Romania (169 cases), Belgium (130 cases) and Italy (126 cases). On 25 May 2024, 4 measles cases were reported from the Canary Islands since the WHO declared Spain free of endemic measles transmission. On 28 May 2024 (in Romanian), Romania was reported to have recorded 16,587 confirmed cases of measles and 16 deaths since the beginning of 2024. Cases were centred around Brasoz city (2,003 cases), Mures county (1,204 cases) and Bucharest city (1,591 case).

Within the UK, Public Health Wales announced that an ongoing outbreak (total 17 cases) in Gwent appeared to have slowed after no new cases have been identified since 20 May 2024. England reported 368 measles cases during May 2024.

Hepatitis E

On 8 May 2024, the WHO published a Disease Outbreak News report on a new hepatitis E outbreak in Chad. The WHO was notified via the International Health Regulation (IHR) National Focal Point (NFP) of Chad to an unusual increase in acute jaundice cases. By 26 May 2024, Chad had recorded a cumulative case count of 1,503 suspected cases (36 confirmed) and 5 deaths (CFR of 0.3%). These cases have been centred around 5 refugee camps and 2 refugee transit sites in Adre and Hadjer-Hadid health districts. 25 cases and 2 deaths were in pregnant woman. Children under the age of 4 years old accounted for 31% of the confirmed cases.

The WHO has assessed the risk of this outbreak as high at the national level due to a continuous movement of people between refugee camps and host communities. Refugees, the majority being women and children, have been fleeing ongoing conflict in Sudan, and there is a moderate risk at the regional level for the spread of hepatitis E back into Sudan or into neighbouring Central African Republic.

Parvovirus B19

The ECDC published a Threat Assessment Brief on human parvovirus B19 (B19V) following an increase in detections across EU and EEA member states in 2024. Parvovirus B19 is not a disease that is under systematic surveillance within the EU, therefore the published brief serves to raise awareness amongst public health professionals and authorities.

14 EU and EEA countries have reported an increase in B19V detections in 2024 compared to 2023. These countries were: Czechia, Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, the Netherlands, Norway, Slovakia and Spain. It is important to note that some of these detections were through seroprevalence studies in blood and plasmid donors. 

Denmark reported 250 B19V cases in 2024, with a previous epidemic occurring in 2017 with 671 recorded cases. Ireland reported 116 confirmed cases in 2023 versus between 30 and 61 cases annually between 2020 and 2023. Latvia has reported 58 cases so far in 2024, compared to between 0 and 6 cases during the previous 5 years.

The ECDC has assessed the risk of B19V to the general population as low. The risk is considered low to moderate for pregnant women and moderate for immunosuppressed people and those with chronic haematological diseases.

Yellow fever

Between 1 January and 31 May 2024, the Africa CDC reported 415 yellow fever cases (20 confirmed cases) and 6 deaths (CFR of 1.45%), across 6 African Union Member States including Central African Republic, Cameroon, Republic of the Congo, Gabon, South Sudan and Uganda. Most cases have been reported in the Republic of the Congo (208 cases, 0 deaths) and Sudan (115 cases, 6 deaths).

In the Americas Region, deaths from yellow fever have been reported by Brazil and Bolivia. On 31 May 2024 (in Portuguese), Brazil reported fatal case of yellow fever infection in Sao Paulo state (dating back to April 2024). On 22 May 2024 (in Spanish), Bolivia reported 2 fatal yellow fever cases in the La Paz region.

Polio

Circulating vaccine derived polio virus (cVDPV)

During May 2024, the Global Polio Eradication Initiative (GPEI) reported 3 cases of cVDPV1 in the Democratic Republic of the Congo (DRC). In 2023, 134 cases were reported across 3 countries: the DRC (106 cases), Madagascar (24 cases), Mozambique (4 cases).

During May 2024, reporting from the GPEI and Africa CDC reported 35 cases of cVPDPV2 from 9 countries: Angola (1 case), Nigeria (13 cases), Chad (1 case), Guinea (2 cases), DRC (3 cases), Guinea, (2 cases), Ethiopia (7 cases), Niger (1 case, first report since 2023), Yemen (5 cases). A total of 390 cases were reported across 22 countries in 2023, with most cases reported from the DRC (118 cases), Nigeria (87 cases) and Guinea (47 cases).

Wild poliovirus type 1 (WPV1)

On 14 May 2024, an independent Polio Outbreak Response Assessment team recommended the WPV1 outbreak in Malawi and Mozambique to be declared over as there has been no evidence of ongoing WPV1 transmission.

On 25 May 2024, the third case of WPV1 was reported by Pakistan. All 3 cases in 2024 have been reported from the Balochistan province which borders Afghanistan. All cases were genetically related to the YB3A cluster which was eradicated from Pakistan in 2021 but re-emerged from Afghanistan through cross-border transmission in 2023. In 2023, 6 cases of WPV1 were reported from Pakistan.

Publications of interest

Avian influenza A(H5N1)

Reverse transcription polymerase chain reaction (rRT-PCR) is considered a gold standard for molecular diagnosis and subtyping of avian influenza due to its high sensitivity and specificity. However, it is limited to a single target and thus multiple parallel PCRs and/or samples are required to identify the viral subtype. This study reports a newly developed multiplexed H5/H7/H9 rRT-PCR with 100% specificity without cross-reacting with other avian influenza subtypes or decreasing the diagnostic sensitivity.

Two recent avian influenza A(H5N1) mammalian transmission studies in ferrets and pigs using a mink derived variant of avian influenza A(H5N1) clade 2.3.4.4b (A/Mink/Spain/3691-8_22VIR10586-10/2022) sought to understand transmission risk dynamics in these mammals. Ferret experiments showed the virus was able to transmit via direct contact to 75% of exposed ferrets and airborne transmitted to 37.5% of exposed ferrets. A single mammalian adaptation was responsible for reducing mortality and increasing airborne transmission. In contrast, the pig experiments showed a minimal ability of the virus to spread via direct or airborne transmission pathways.

Arboviruses

A recent study in France assessed whether a specific subpopulation of Aedes albopictus mosquitoes would have the potential to transmit 5 arboviruses (chikungunya, dengue, Usutu, West Nile and Zika viruses). In Sweden, Culex pipiens mosquitoes were assessed for their potential to transmit Japanese encephalitis virus. Aedes albopictus from Italy, Anopheles atroparvus from Spain and Culex pipiens from Belgium have also been exposed to Mayaro virus to assess their potential in sustaining transmission in Europe. In all 3 studies, mosquito vectors showed the potential to carry and spread the viruses tested: indicating a potential future risk for sustained transmission and establishment of arboviruses in Europe.

Seoul virus

Seoul virus (SEOV) is an orthohantavirus that can cause haemorrhagic fever with renal syndrome in humans. Wild rats in an urban park in Lyon, France, were sampled with 17.2% of rats returning a positive seroprevalence result. Samples from seropositive rats were sequenced; successfully yielding 7 complete or near complete SEOV genomes. All isolates were classified within a previously defined lineage 7. Further analysis found that the virus was slowly undergoing evolution over the past decade in the area, potentially highlighting viral adaptation. Targeted surveillance of the rats would be beneficial to understand the risk of zoonotic spillover.

Tularaemia

Tularaemia is a disease that affects humans, domestic and wild animals. A recent systematic review and meta-analysis determined tularaemia presence in 22 Eastern Mediterranean Region countries. The analysis indicated that tularaemia is an endemic and neglected disease in this region. Although there are studies across the individual themes of human population, reservoirs, and vectors in all Eastern Mediterranean countries, comprehensive studies on tularaemia in a one health context is lacking.

Monkeypox virus

During the 2022 global outbreak of mpox, the UK’s Vaccine Development and Evaluation Centre (VDEC) rapidly developed a new assay that allowed clinicians to tell the difference between individuals infected with mpox and those that had received the smallpox vaccine. This capability also allowed researchers to identify the markers (antigens) that the human immune system recognised to inform future mpox vaccine design. It also verified that those vaccinated with the smallpox vaccine had cross immunity against mpox, thus providing evidence to public health officials that this was a valid prevention measure for those at the highest risk. The original research paper can be accessed here.

Novel pathogens and diseases

Spotted Fever Group (SFG) Rickettsia

SFG Rickettsia are a vector-borne bacteria that is the causative agent of rickettsioses. Within SFG Rickettsia, a lack of diagnostic tools prevents the differentiation between Rickettsia species that cause human infection, namely R. rickettsii (Rocky Mountain spotted fever), R. parkeri (Rickettsia parkeri rickettsiosis), Rickettsia 364D (Pacific Coast tick fever) and R. akari (rickettsialpox). This case study developed a real-time PCR specific assay which identified a novel Rickettsia CA6269 in 2 patients in California nearly 20 years apart. Future use of this assay will allow clinicians to identify the contribution of this pathogen to SFG rickettsioses in the US.

Further reading

The effect of temperature on the boundary conditions of West Nile virus circulation in Europe

ECDC One Health Framework within the EU and EEA

Global Report on Neglected Tropical Diseases 2024

Worldwide distribution, symptoms and diagnosis of the coinfections between malaria and arboviral diseases: A systematic review

Related resources

High consequence infectious diseases monthly summaries

National flu and COVID-19 surveillance reports

Avian influenza (influenza A H5N1): technical briefings

Avian influenza (bird flu) in Europe, Russia and the UK reports

Bird flu (avian influenza): latest situation in England updates

Human Animal Infections and Risk Surveillance (HAIRS) group risk assessments and statements

Animal and Plant Health Agency (APHA) monitoring of disease in livestock and poultry monthly reports

Authors of this report

UKHSA’s Emerging Infections and Zoonoses team epiintel@ukhsa.gov.uk