Research and analysis

Infectious disease surveillance and monitoring for animal and human health: summary April 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	New
Cholera	Comoros and Mayotte	New

Avian influenza A(H5N1) – United States

Event summary

In April 2024, the World Health Organization (WHO) reported a confirmed human case of avian influenza A(H5N1) in Texas state, United States of America (US). The case, a dairy farm worker, developed conjunctivitis (their only symptom) on 27 March 2024, following exposure to dairy cattle presumed to be infected with avian influenza A(H5N1) virus. The case did not require hospitalisation, was treated with oseltamivir and recovered. No additional human cases associated with this case have been identified. Highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b was confirmed in specimens taken from the case following tests at the US Centers for Disease Control and Prevention (US CDC) on 30 March 2024. The genotype was classified as B3.13, a reassortant virus of Eurasian - North American origins, which was the same genotype detected in dairy cattle in Texas. This genotype has only been reported in the US, with the first detections in wild bird reported in November 2023.

In March 2024, the US Department of Agriculture (USDA) reported detections of avian influenza A(H5N1) in dairy cattle on farms in Texas and Kansas for the first time. Since then, and up to 30 April 2024, avian influenza A(H5N1) has been detected in 36 dairy cattle herds across 9 states in the US (Figure 1), including Texas (n=12), New Mexico (n=8), Michigan (n=6), Kansas (n=4), Idaho (n=2), and one detection each in Ohio, South Dakota, Colorado, and North Carolina.

Figure 1: Geographical distribution of avian influenza A(H5N1) detections in dairy cattle herds in the United States, up to 30 April 2024.

Texas (TX) New Mexico (NM), Michigan (MI), Kansas (KS), Idaho (IO), Ohio (OH), South Dakota (SD), Colorado (CO), and North Carolina (NC). Adapted from the US Department for Agriculture. Accessed: 21 May 2024.

Incident assessment

This is the second known human infection with avian influenza A(H5N1) reported in the US, with the first case reported in 2022. Globally, between January 2003 to 1 April 2024, 889 cases of human infection with avian influenza A(H5N1) virus and 463 deaths (case fatality rate (CFR) of 52%) were reported from 23 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 Department for Environment, Food and Rural Affairs and 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. At this time, based on a preliminary risk assessment, there are no indicators of increasing risk to human health. The Food Standards Agency (FSA) 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.

Cholera – Comoros and Mayotte

Event summary

Comoros has been experiencing a cholera outbreak since February 2024. This follows the importation of cases from neighbouring Tanzania, where a cholera outbreak has been ongoing since September 2023. In Comoros, between 1 January and 28 April 2024, 3,244 cholera cases and 67 associated deaths (CFR of 2.1%) have been reported across all 3 islands (Ngazidja, Ndzuwani, and Mwali). Most cases and deaths have been reported on the Island of Ndzuwani (2,443 cases, 48 deaths). The 2,566 new cases and 50 deaths reported during April 2024 represent a 379% and 355% increase in cases and deaths, respectively, compared to March 2024. Comoros is not considered endemic for cholera; the last cholera outbreak was reported in 2007, also following case imports.

Mayotte declared a cholera outbreak in April 2024, following the arrival of imported cases on boats from neighbouring Comoros and East Africa. Since the detection of the first imported case in Mayotte on 18 March 2024, 26 cholera cases (no deaths) have been reported as of 26 April 2024. Of these, 16 cases, reported from the commune of Koungou, had been locally acquired, while 10 cases were imported. Prior to this outbreak, no cholera cases had been detected in Mayotte since 2000.

Incident assessment

Cholera is an acute diarrhoeal illness spread predominantly by the consumption of food and water contaminated with Vibrio cholerae. Over the last 2 years, outbreaks of cholera have affected 18 countries within the WHO African Region. Severe weather and flooding in the region has contributed to continued cholera transmission. Globally, countries experiencing natural disasters, poverty and reduced access to clean drinking water are at increased risk of cholera outbreaks.

The WHO classify the global resurgence of cholera as a grade 3 emergency, and continue to assess the risk of cholera at a global level as very high. This is due to the depletion of stocks of cholera vaccines and treatments, global expansion and a large number of outbreaks currently being reported.

Even though numerous cholera outbreaks have been documented globally, only a small number of cases are recorded annually among travellers returning to the UK. In 2023, there were 17 confirmed cases of cholera in UK travellers. The risk of a cholera outbreak in the UK is extremely low due to high standard sanitary infrastructure and hygiene practices.

Disease or infection	Location
Avian influenza A(H10N3)	China
Avian influenza A(H9N2)	Vietnam
Cholera	multi-country
Dengue	multi-country
Polio	multi-country
Psittacosis	Argentina
Swine influenza	United States
West Nile virus	Spain

Avian influenza A(H10N3)

On 2 April 2024, health authorities in China reported a confirmed human case of avian influenza A(H10N3), in a 51 year old male, who developed symptoms on 28 February 2024. The case is a farmer from Yunnan Province, China, who reported exposure to poultry. No additional cases were detected amongst contacts of the case. Globally, up to 3 May 2024, a total of 3 human cases with avian influenza A(H10N3) infection have been reported, all of which were from China.

Avian influenza A(H9N2)

On 19 April 2024, the WHO reported a confirmed human case of avian influenza A(H9N2), in a 37 year old male from Vietnam. The case developed symptoms on 10 March 2024, and was reported to be living near a poultry market in Tien Giang Province. This is Vietnam’s first ever reported human case of avian influenza A(H9N2). As of 19 April 2024, 99 cases of human infection with avian influenza A(H9N2), including 2 deaths, have been reported globally to WHO since 2015.

Cholera

During April 2024, 27,696 new cholera cases and 281 associated deaths were reported from 19 countries and territories across 4 WHO regions. This is a similar number of cases and a 31% increase in deaths compared to the previous month. Most cases were reported in the Eastern Mediterranean Region (14,541 cases and 41 deaths across 5 countries), followed by the African Region (13,126 cases and 240 deaths across 12 countries).

On 19 April 2024, Brazil’s Ministry of Health reported a locally acquired cholera case (in Portuguese). The case, a 60 year old male in Salvador, Bahia State, reported no recent travel history to countries reporting cholera outbreaks, or contact with any suspected or confirmed cholera cases. This is the first locally acquired case reported in Brazil since 2005.

The WHO reported that between January and March 2024, the global stockpile of cholera vaccines was completely depleted. On 12 April 2024, the WHO prequalified Euvichol-S, a new inactivated oral cholera vaccine. This new vaccine has a similar efficacy to existing vaccine with a simplified formulation, which increases the potential of production capacity.

Dengue

Between 1 January and 26 April 2024, the Africa Centres for Disease Control and Prevention (Africa CDC) reported 35,858 dengue cases (7,439 confirmed cases) and 49 deaths across 10 African Union Member States. Most cases have been reported in Burkina Faso (21,352 cases, 38 deaths), Mauritius (6,779 cases, 5 deaths) and Ethiopia (1,725 cases, 2 deaths). In 2023, 280,218 dengue cases and 808 deaths were reported in 18 African Union Member States, with Burkina Faso reporting the highest numbers (242,425 cases and 709 deaths). Data should be interpreted with caution due to differences in case definitions, laboratory capacities and reporting capabilities across African Region countries. The true burden of disease within these countries is likely an underestimation.

In the Region of the Americas, the WHO has reported 7,327,521 suspected dengue cases and 3,215 deaths between 1 January and 29 April 2024. This is a 243% increase in cases compared to the same period in 2023, and a 445% increase compared to the average of the last 5 years. Most cases reported during week 17 of 2024 were reported in Brazil (303,708 cases), Argentina (41,526 cases) and Peru (11,698 cases).

On 26 April 2024, Fiji’s Ministry of Health and Medical Services declared a dengue outbreak following an increase in cases. Since the beginning of 2024, an exceedance in cases have been reported in Ovalau (72 cases) and the Western Division (370 cases). The increase in cases is attributed to adverse weather conditions in March and April 2024.

Several countries across Asia have been reporting an increase in dengue cases in recent months. In 2024, up to 20 April 2024, 50,650 dengue cases, including 39 deaths have been reported in Malaysia, according to the WHO. This is a 44% increase compared to the same period in 2023 (35,202 cases, 22 deaths). Thailand has reported 26,527 dengue cases, including 22 deaths in 2024, up to 25 April 2024. This compares to 15,630 cases and 16 deaths reported during the same period in 2023. Indonesia has been experiencing a recent surge in dengue cases. In 2024, up to 8 April 2024, the country reported 60,296 cases and 455 deaths, with most cases reported in Tangerang Regency (2,540 cases). A total of 114,20 cases including 894 deaths were reported across Indonesia in 2023.

Polio

Circulating vaccine derived polio virus (cVDPV)

During April 2024, the Global Polio Eradication Initiative (GPEI) reported one case of cVDPV1in 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 April 2024, the GPEI reported 13 cases of cVDPV2 from Burkina Faso (one case), Chad (one case), Nigeria (6 cases), Somalia (one case), South Sudan (3 cases) and Yemen (one case). 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).

Psittacosis

On 20 April 2024 (in Spanish), the Argentinian Ministry of Health reported a recent increase in cases of psittacosis. 62 confirmed and 14 probable cases were reported in 2024 up to epidemiological week 15. This represents a 27% increase in confirmed cases compared to the whole of 2023 (49 confirmed and 9 suspected cases). In 2024, Buenos Aires has reported an 87.5% increase in cases compared to the same period in 2023, while Entre Ríos has reported a 62.5% increase. 

Swine influenza A(H1N1)v

In April 2024, the US CDC reported first human case of swine influenza A (H1N1)v in the US for 2024. The case, a child from Pennsylvania state, had contact with pigs prior to symptom onset. The case required hospital care following infection but has since recovered. Investigations identified 2 close contacts of the case who had developed mild symptoms (prior to the case’s symptom onset). These individuals, who have fully recovered, also had contact with pigs but were not tested for influenza.

West Nile virus

On 19 April 2024, Spanish health authorities (in Spanish) reported a confirmed case of West Nile virus (WNV) in a 5 year old child in Lebrija, Seville, in Spain. The European Centre for Disease Prevention and Control stated that the case is unusual, but not unexpected due to milder weather conditions and an increase in mosquito activity. No further cases have been reported, suggesting that it may be an isolated incident and not an indication of an early start to the usual transmission season (early summer). In 2023, across the European Union and European Economic Area, 707 cases of WNV were reported, of which Spain reported 17 confirmed cases.

Publications of interest

Crimean-Congo haemorrhagic fever (CCHF)

The first autochthonous human case of CCHF in Northwest Spain was reported in June 2021, which was followed by 2 additional cases in 2022. These cases were reported in the El Bierzo region. Following investigations, CCHF virus (CCHFV) was detected in 10.5% of non-Hyalomma questing ticks collected in the region. This study provides evidence of CCHFV circulation in Northwest Spain. Further work is needed to understand the potential role that non-Hyalomma tick species may play in CCHFV transmission.

Dengue

Among the French Caribbean Islands, epidemics of dengue virus serotype 2 (DENV-2) were simultaneously declared in Guadeloupe and Martinique on 17 August 2023. Following this, DENV-2 epidemics were later declared on the islands of Saint-Barthélemy and Saint-Martin, and detected in circulation in French Guiana, as well as in Mainland France. A recently published study reported the establishment of a single epidemic lineage amongst these territories, which was also found to be the causative strain amongst autochthonous clusters reported in mainland France. The authors highlight the need for continued surveillance to prevent the inter-territorial spread of dengue virus and its introduction to non-endemic areas.

Filoviruses

A recently published study combined variable fragments from pan-ebolavirus monoclonal antibodies (mAbs) and Marburg virus mAbs to create pan-filovirus protective bispecific antibodies. The authors found the bispecific antibodies were able to protect mice against lethal exposures to Ebola and Marburg viruses and were less susceptible to acquiring resistance mutations.

Malaria

A recent study reports that the mosquito species, Anopheles Sacharovi, which was considered to have disappeared from Italy over 50 years ago, was rediscovered in Lecce municipality, Apulia region, Italy (specimens were collected in 2022 and 2023). The authors conclude the results provide a basis to review the prediction and expansion models of introduced malaria in Italy and the need to strengthen surveillance.

Results of a phase 2 trial in 268 children across Mali, showed that the subcutaneous administration of the L9LS monoclonal antibody was well tolerated and provided up to 70% efficacy against malaria infections over a 6 month period. The authors concluded that the development of monoclonal antibodies should be used in combination with additional tools to reduce the burden of malaria.

Measles and rubella

The recently published results of a phase 1/2 trial in infants, toddlers, and adults in the Gambia, report that the administration of a measles and rubella microneedle patch vaccine, MRV-MNP, was well tolerable and immunogenic among the participants. The patch was found to elicit 93% measles and 100% rubella seroconversion in infants, compared to 90% measles and 100% rubella in those receiving a subcutaneous injection. The authors concluded that the results of the study support further investigations into the development of the MRV-MNP as a method of vaccine administration.

Mpox

On 10 April 2024, the US Food and Drug Administration (FDA) granted Emergency Use Authorization (EUA) for Labcorp’s mpox PCR (polymerase chain reaction) Test Home Collection Kit. This is the first mpox at-home collection kit to be granted EUA from the FDA. The results are electronically delivered to the prescribing physician and patient, aiming to aid in early detection and management of mpox infections in the US.

On 27 April 2024, the National Institute of Allergy and Infectious Diseases reported the results of a dose-sparing study for the modified Vaccinia Ankara-Bavarian Nordic mpox vaccine. The study, which enrolled 225 adults in the US with no prior vaccination against mpox or smallpox, found that 2 weeks after the second vaccine dose, participants who received one fifth of the standard dose had an antibody level equivalent to those on the standard MVA-BM regimen. However, the findings cannot predict the efficacy of dose-sparing regimens with certainty, as there are no defined measures of immune processes needed to protection against mpox.

Tuberculosis

Results of a phase 1 trial in adults in the United Kingdom showed that the aerosolised administration of the BCG vaccine, mimicking the natural route of Mycobacterium tuberculosis infection, was found to be sufficiently well tolerated. The authors conclude this to be the first study in humans to deliver aerosol-inhaled BCG to M. tuberculosis-naive and BCG-naive participants, with results indicating the need for further investigations into this method of vaccine administration.

Zika virus

It is difficult to estimate the true burden of ZIKV infection globally due to the high number of asymptomatic infections and differential diagnosis amongst the other arboviruses. A systematic review of 84 studies across 49 countries and territories found evidence of IgG antibodies across all WHO regions, excluding Europe. Seroprevalence study findings ranged from 39.9% in the Americas to 8.4% in Africa, with the exception of Burkina Faso (22.8%) and Gabon (43.7%). Notably, a seroprevalence of 16.0% was found in the Eastern Mediterranean, despite no reported autochthonous transmission.

The antigenic similarity between ZIKV, dengue virus and other members of the Flaviviridae family makes their differential diagnosis challenging due to the cross-reactivity of their antibodies. A study developed 3 ZIKV antigens for use in ELISA tests to detect anti-ZIKV IgG, in ZIKV, dengue and chikungunya virus positive human sera. The antigens were able to detect ZIKV without cross-reactivity with up to 95% sensitivity and 97% specificity. The authors provide evidence of the potential use of these antigens in the development of ZIKV specific diagnostic tests.

Novel pathogens and diseases

Dadong virus

A recently published study reported a novel orthonairovirus named Dadong virus (DDV), which was detected in Haemaphysalis concinna ticks in Dadong Village, on the China-North Korea border. Further serological evidence of DDV circulation in cattle and mice were also found in the area. The authors report the need for serological investigations using human samples to assess the potential public health risk posed by DDV.

Further reading

Global burden of disease

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

Global burden associated with 85 pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019

Polio

Surveillance To Track Progress Toward Polio Eradication — Worldwide, 2022–2023

Related resources

1. High consequence infectious diseases monthly summaries

2. National flu and COVID-19 surveillance reports

3. Avian influenza (influenza A H5N1): technical briefings

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

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

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

7. 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