Research and analysis

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

Updated 6 March 2025

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1. 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

2. Notable incidents of public health significance

2.1 Summary of incidents

Disease or infection Location New or update since the last report
Mpox African Region Update
Chandipura virus India Update

2.2 Mpox - African Region

Event summary

On 14 August 2024, the World Health Organization (WHO) declared the resurgence of mpox to be a public health emergency of international concern, requiring a coordinated international response. This was due to the continued increase in reported mpox cases from African countries, and notably the spread of a new clade of mpox (designated clade Ib) in the east of the Democratic Republic of the Congo (DRC) and into its neighbouring countries including Burundi and Uganda. 

 Simultaneously, countries in West Africa such as Nigeria have continued to report clade II mpox cases. Up to the end of August 2024, Nigeria has reported 48 confirmed cases so far in 2024. This is a lower number compared to the same period in 2023 when Nigeria reported 80 confirmed cases. The US has been supporting mpox response efforts in Nigeria through the provision of the Bavarian Nordic MVA-BN vaccine. These vaccines will be used to vaccinate healthcare workers and other at-risk groups in the 13 Nigerian states affected by mpox. Other countries such as Cameroon have also continued to report mpox cases which have so far been clade typed to be clade II (official reports from July 2024).

 To the end of August 2024, countries in West Africa, as well as northern and southern African countries continue to report cases of clade II mpox. Countries in central and eastern Africa have reported clade Ia mpox. Countries including the DRC, Burundi, Kenya, Rwanda and Uganda have reported clade Ib mpox cases (see Figure 1). Cameroon is the only country where both clades I and II mpox have been reported. The trajectory of clade I mpox cases reported in the African region can be seen in Figure 2.

Figure 1. Geographical distribution of mpox clades in the African region. Since March 2024, clade Ib mpox emerged from the DRC and in July 2024 geographically expanded to Burundi, Kenya and Uganda. Clade Ia mpox has continued to circulate in the DRC. Sporadic clade Ia cases have continued to be reported from the ROC and Central African Republic. Data from the WHO.

The majority of cases in the African region have been reported from the DRC, with Equateur and South Kivu provinces reporting over 6,000 cases each since the beginning of 2024. Between 1 January and 31 August 2024, a total of 19,750 cases (14,856 suspected; 4,894 confirmed) and 632 deaths (case fatality rate of 3.2%) were reported in the DRC. Testing coverage in the DRC remains low due to limited testing capacity, and thus, under-ascertainment of cases is likely. The outbreak in the DRC is characterised by the geographical divide of clade Ia and clade Ib mpox. During August 2024, clade Ia mpox has continued to spread in Equateur province and other endemic provinces and has since spread to Kinshasa. Clade Ib mpox was previously restricted to North and South Kivu but has since been reported from Kinshasa too, making this the only DRC province with both clades detected. Sequencing capacity in the DRC remains limited and therefore the full picture of clade distribution may be broader than the cases that are currently sampled.

 After the DRC, Burundi is the next most affected country. 1,029 mpox cases (748 suspected; 281 confirmed) were reported between 27 July and 31 August 2024 from 29 out of 49 health districts. Burundi reported mpox for the first time in July 2024 and is currently experiencing sustained community transmission of clade Ib mpox. The hotspot of the current outbreak is located in Bujumbura City consisting of 3 health districts (Bujumbura North, Centre and South). 53% of the confirmed cases have been reported in males, with children aged under 15 years also accounting for 53% of the confirmed cases.

 Other countries reporting clade Ib mpox in August 2024 include Kenya (3 new confirmed cases), Rwanda (2 new confirmed cases) and Uganda (5 new confirmed cases). Most of these were travel-associated cases, some of these cases had a travel history to the DRC.

 Between 2 August and 31 August 2024, 16 new confirmed mpox cases were reported in the Central African Republic, bringing the cumulative total to 48 confirmed cases across 6 out of 7 health regions. An mpox outbreak was declared on 26 July 2024, in the capital, Bangui. Prior to this declaration, previous mpox outbreaks were reported from rural, often forested areas, in the south of the country. Clade Ia mpox was sequenced from some of these confirmed cases.

 The ROC reported 2 new confirmed cases of mpox in August 2024, bringing the cumulative case count to 21 confirmed cases. Although the clade type has not been reported in the ROC, clade Ia mpox is known to circulate in the ROC. During 2023, the ROC reported 95 mpox cases and 5 deaths.

Figure 2. The epidemiological curve for confirmed cases of clade I mpox in the African region. Data was line listed from official and media sources with a cutoff date of 31 August 2024.

Notably on 15 August 2024, the first exported case of clade Ib mpox was reported outside the African region in Sweden. The case had a recent travel history to an African country experiencing mpox transmission. On 22 August 2024, the second exported case of clade Ib mpox was officially confirmed by Thailand. The case had a recent travel history to South Kivu Province, DRC. Health officials identified 43 contacts that will be monitored for the next 21-day period.

2.3 Incident assessment

During August 2024, the epidemic situation in the DRC and Burundi has continued to deteriorate with an increase in cases (and deaths in the DRC only). During August 2024, the first ever cases of mpox were reported in Uganda, with travel links to the DRC, highlighting the risk of transmission across national borders in the African Region. Travel-associated clade Ib mpox cases were also reported outside of the African Region for the first time in Sweden and Thailand. No further onwards transmission were observed from these exported cases.

The WHO has classified the risk associated with mpox in eastern DRC and neighbouring countries as high. The WHO states that the mpox outbreak in Africa may continue to evolve due to multiple factors. For example:

  • there is evidence that there is likely under-detection of cases and under-reporting of local transmission with reported cases that have no epidemiological links

  • reported cases have been identified in multiple locations within each country

  • emergency responses in each country have been disparate with varying levels of resource allocation and support from in-country and global partners

  • clade I mpox is reportedly being transmitted through sexual contact within key populations, further accelerating its spread

Several studies were published in August 2024 that used whole genome sequencing of virus to investigate transmission dynamics of mpox in Africa. This included:

As of 31 August 2024, no cases of clade I mpox have been reported in the UK, and this clade has not been implicated in the international mpox outbreak in non-endemic countries that started in mid-2022. In the UK, clade I mpox is considered a high consequence infectious disease (HCID), for which there are established processes for the isolation and contact management of a HCID case. There are a range of robust public health, clinical, infection prevention and control measures available for HCIDs, which can be adapted for use, as necessary.

2.4 Chandipura virus - India

Event summary

During August 2024, the Chandipura virus (CHPV) outbreak in India was reported to have abated, with a declining trend in cases observed since 19 July 2024. On 23 August 2024, the WHO reported that the India Ministry of Health and Family Welfare (MoHFW) had reported 245 cases of acute encephalitis syndrome (AES) and 82 associated deaths (case fatality rate of 33%), from when the outbreak began in early June to 15 August 2024.

Of the reported cases, 64 cases (61 from Gujarat State and 3 from Rajasthan State) were laboratory confirmed. To date, no human-to-human transmission of CHPV has been recorded.

 In response to the outbreak, the India MoHFW deployed a specialised outbreak response team to Gujarat to assist with epidemiological investigations and the implementation of public health measures. Other measures initiated at the national level included the activation of vector control measures, health awareness campaigns, advisory and coordination measures across state-lines and virological research into the current outbreak.

2.5 Incident assessment

CHPV is a vector-borne disease transmitted by sandflies, mosquitoes and ticks and is known to cause irregular outbreaks of AES in western, central and southern parts of India, particularly around the monsoon season. CHPV has a high case fatality rate between 56% to 75% based on previous outbreaks in India. Historically, children under the age of 15 years have been most affected, with AES symptoms occurring rapidly within 48 to 72 hrs of symptom onset. No specific vaccine or treatment is available to prevent or treat CHPV infection.

India’s current CHPV virus outbreak is the largest  to occur during the last 20 years. The second largest outbreak was reported in 2003 in Andhra Pradesh State (resulting in 329 suspected cases and 183 deaths). CHPV outbreaks tend to occur every 4 to 5 years in Gujarat state.

The WHO assessed the risk of this  outbreak as moderate at the national level based on the following factors: high case fatality rate, a lack of specific treatments or vaccines and the high demand on medical and public health resources during an outbreak. The WHO has recommended vector control measures and protection against bites of sandflies to reduce the further spread of CHPV.

2.6 Summary of other incidents

Disease or infection Location
Oropouche fever Multi-country
Eastern equine encephalitis (EEE) United States
West Nile virus (WNV) Multi-country
Influenza A variant viruses Multi-country
Polio Multi-country

2.7 Oropouche fever

During August 2024, Brazil continued to experience an upsurge of Oropouche fever cases with a cumulative total (for 2024) of 7,767 cases and 2 deaths as of 25 August 2024. The states of Amazonas (3,230 cases), Rondônia (1,710 cases), and Bahia (886 cases) have reported the highest numbers of cases during 2024. In addition, one suspected death was reported on 29 August 2024 in the state of Parana. Notably on 3 August 2024, the Brazil Ministry of Health confirmed a fatal foetal death cause by the vertical transmission of Oropouche fever in the state of Pernambuco, with a further 8 suspected vertical transmission cases still under investigation by health authorities. On 9 August 2024, a fatal case that also had foetal congenital anomalies associated with vertical transmission of Oropouche fever was reported in the media. 

 On 7 August 2024, media in Colombia reported 87 confirmed cases  since the beginning of 2024, with 2 cases reported in pregnant women. On 28 August 2024, 506 cases were reported from all 15 provinces of Cuba, which reported Oropouche fever cases for the first time at the end of May 2024.

 On 28 August 2024, the Dominican Republic Ministry of Health issued an epidemiological alert for Oropouche fever after retrospective analysis of previously undiagnosed human biological specimens returned positive test results for Oropouche virus (OROV). These specimens had previously returned a negative test result for dengue virus. Authorities stated that no active OROV cases were present in the Dominican Republic.

 On 13 August 2024, the Ministry of Health for the Canary Islands reported their first ever imported case of Oropouche fever. On 21 August 2024, Florida’s Department of Health reported 9 new cases of Oropouche fever. All of these cases had a travel history to Cuba.

 On 3 August 2024, the Pan American Health Organisation (PAHO) published a formal rapid risk assessment that detailed the recent change to the risk level from moderate to high. The assessment stated that this uprating was due to the increase and expansion of OROV cases outside of endemic areas, the first ever reported associated deaths due to OROV infection, and the first-ever reports of vertical transmission with OROV and associated foetal deaths and congenital defects.

 As a result of exported OROV cases occurring since June 2024, the European Centre for Disease Prevention and Control (ECDC) published a risk assessment stating that the likelihood of infection for EU/EEA citizens travelling to or residing in endemic areas in South and Central America is currently assessed as moderate. On 16 August 2024, the US Centers for Disease Control and Prevention (CDC) issued a Health Alert Network Health advisory to notify US clinicians and public health authorities about the increase in OROV infections within the Americas region. The US CDC has not issued a risk level rating for OROV.

2.8 Eastern equine encephalitis (EEE)

During August 2024, 4 different US states reported human cases of EEE:

Between January and August 2024, a total of 5 human cases of EEE were reported for the United States, compared to 7 human cases reported for the whole of 2023.

On 30 August 2024, New Jersey reported a retrospective human case that occurred during July 2024. During the month, an unvaccinated horse also tested positive for EEE. 1 mosquito pool tested positive for EEE in Monmouth County. On 27 August 2024, New Hampshire reported their first fatal human case of EEE since 2014. New Hampshire has also detected EEE virus in a horse and 7 mosquito pools to date.

 On 16 August 2024, Massachusetts announced their first EEE case for 2024. The Massachusetts Department of Health subsequently increased the risk levels across a number of counties, with some counties rated as ‘critical’ for the risk of exposure to EEE virus. A second case of EEE case was reported on 29 August 2024. During August 2024, media had widely reported that some local communities in Massachusetts had restricted outdoor activities in the evening to prevent getting bitten by infected mosquitoes. Massachusetts health officials first reported the detection of EEE virus in mosquitos on 3 July 2024. Health officials responded widely with vector control measures through the use of aerial and lorry-based spraying across multiple counties.

 On 9 August 2024, Vermont retrospectively reported a human case of EEE from July 2024. Vermont’s Department of Health received confirmatory test results from the US CDC on 8 August 2024. Mosquitoes collected from multiple counties in the state tested positive for EEE virus.

EEE is a nationally notifiable disease in the US. The most up to date data for EEE cases in the US can be found on the US CDC page.

2.9 West Nile virus (WNV)

Within the European Union, European Economic Area and EU-neighbouring countries (Albania, Bosnia and Herzegovina, Kosovo, Montenegro, North Macedonia, Serbia and Turkey), during the month of August (week 32 to 35), 270 new cases of WNV were reported to the European Centres for Disease Preventing and Control (ECDC). As of 28 August 2024, a cumulative total of 325 cases of West Nile Virus were reported. Most cases were reported from Italy (n=104), Greece (n=88), Serbia (n=30). 4 new countries reported their first WNV cases for 2024; Albania, Bulgaria, Kosovo, Germany. During August 2024, the following countries also reported new deaths associated with WNV infection:

  • Bulgaria (n=2)
  • Greece (n=9)
  • Italy (n=2)
  • Romania (n=3)
  • Spain (n=5).

    On 25 August 2024, media in Turkey reported 21 cases of WNV. On 30 August 2024, the National Institute of Public Health of the Republic of Slovenia reported their first 3 cases of WNV for 2024 with their last reported case in 2019. Moldova also reported their first WNV case since 2019, in a returning traveller from Italy.

    Between 1 June and 30 August 2024, media in Ukraine reported 17 WNV cases and 3 associated deaths in Kyiv. Between 1 January and 27 August 2024, the media reported that the Republic of Tatarstan (Russia) has recorded 59 cases of WNV.

     Notably, as of August 2024, Israel is currently recording a large outbreak of WNV. Between 5 August and 22 August 2024, 74 new WNV cases and 6 new deaths were recorded, bringing the cumulative total for 2024 to 870 cases and 62 deaths. This is the largest outbreak in recent years, with the previous largest outbreak occurring during 2000 resulting in 425 cases.

     Guadeloupe recorded their first ever human case of WNV on 8 August 2024.

2.10 Swine influenza A variant viruses

During August 2024, the US CDC has recorded 4 cases of swine influenza A variant virus infections in humans (H1N1v; 1 case, H1N2v; 1 case, H3N2v; 2 cases). These cases bring the total of variant influenza A viruses recorded in the US for 2024 to 7 cases. A further human case of influenza A(H1N1)v was reported in Vietnam during August 2024.

Swine influenza A(H1N1)v

On 17 August 2024, Ohio’s state Department of Health reported their first human case of variant influenza A(H1) virus for 2024. This was confirmed to be influenza A(H1N1)v. The case was over 18 years old, developed symptoms (not stated what they were) and was briefly hospitalised and later recovered. This case had exposure to pigs at an agricultural event prior to symptom onset. No follow up cases have been reported amongst close contacts and no human-to-human transmission evens were identified.

 On 19 August 2024, Vietnam reported their first ever fatal case of swine influenza A(H1N1)v in a 70 year old female that had underlying conditions that resided in the Son La province of Vietnam. This case was backdated from June 2024. The case developed symptoms of fever, fatigue and a loss of appetite 7 days after returning from her home village in Hung Yen province. She was later admitted to a hospital after the symptoms persisted, with a further diagnosis of pneumonia added to her medical conditions. A rapid test confirmed influenza A (untyped). She was transferred to the National Hospital for Tropical Diseases and underwent treatment for 6 days before passing away. Epidemiological investigations did not identify any disease outbreaks in livestock around the case’s residence in Son La province or in Hung Yen province. No secondary cases or reports of suspected cases with respiratory symptoms were reported. The exposure source was not identified.

Swine influenza A(H1N2)v

On 17 August 2024, Pennsylvania state Department of Health also reported their first human case of variant influenza A(H1) virus for 2024. This was confirmed to be swine influenza A(H1N2)v. The case characteristics as reported in the public domain were similar to the Ohio case which was recorded in the same US CDC report. This case however, had an occupational exposure to swine.

Swine influenza A(H3N2)v

On 9 August 2024, Michigan’s state Department of Health reported a human case of swine influenza A(H3N2)v in Ingham County, Michigan, United States. This case was backdated to week 30 of 2024 (week ending 27 July 2024). The case was confirmed by the US CDC. This variant virus is commonly associated with exposure to infected pigs. The exposure source was not identified, and no further cases were reported.

 Colorado’s Department of Public Health and Environment also reported a human case of swine influenza A(H3N2)v to the US CDC on the same day as the Michigan case. The case was backdated to week 28 of 2024 (week ending 13 July 2024). Health officials reported the individual (aged 17 years or younger) had attended an agricultural event prior to symptom onset. Close contacts of the case have not reported any symptoms.

2.11 Polio

Circulating vaccine derived polio virus (cVDPV)

During August 2024, the Global Polio Eradication Initiative (GPEI) reported that 8 countries had recorded cases of cVDPV, including:

Wild poliovirus type 1 (WPV1)

On 25 August 2024, Pakistan reported its 4th case of WPV1 during August 2024. This is the 16th cumulative case for 2024. On 28 August 2024, Afghanistan reported its 17th cumulative case of WPV1 for 2024; an addition of 4 WPV1 cases during August.

Notably during August 2024, media reported a suspected case of polio which was later diagnosed as Immunodeficiency-Related Vaccine-Derived (iVDPV) polio in a child living in Meghalaya state, India. India was declared polio-free in 2014 by the WHO. A team from the WHO and Meghalaya’s Department of Health have been deployed to investigate this case.

3. Publications of interest

3.1 Avian influenza A(H5N1)

During March 2024, an outbreak of avian influenza A(H5N1) belonging to clade 2.3.4.4b was identified in dairy cattle in Texas, US. By 1 August 2024, 175 herds of dairy cattle across 13 US states had been affected. A short communication described case symptomology for the 2nd and 3rd human infections of avian influenza A(H5N1) identified in Michigan state following exposure to infected dairy cattle. One case reported that milk had splashed into their eye and the other case had handled bovine oral fluid therapy and oral secretions. Symptomology differed in both cases and both cases also had worn different levels of personal protective equipment worn.

 A molecular study of bovine mammary glands evaluated the level of sialic acid-α2,3 and α2,6-galactose host receptors which are the binding receptor for influenza A viruses. Of note was that expression of sialic acid host receptors were upregulated when cows were peaking in lactation compared to when they were not lactating. The first retail study of commercial dairy products was published as a pre-print by the US Food and Drug Administration during August. A joint risk assessment by global public health agencies: Food and Agriculture Organisation, World Health Organization and the World Organization for Animal health was published on 14 August 2024. The overall global public health risk of avian influenza A(H5N1) was deemed to be low but increasing between low to moderate for individuals that are occupationally exposed to infected animals.

3.2 Mpox

A genomic analysis of mpox clade Ib viruses revealed that one of the target genes used in mpox virus (MPXV) detection assays had a deletion that would affect accuracy and accurate identification of a novel clade Ib MPXV. As a result, a new real-time PCR assay was developed and validated to ensure accurate detection of clade Ib MPXV. During August 2024, the WHO released a new position paper to replace previous interim guidance published in 2022 around the use of small pox vaccines and off-label use.

3.3 Oropouche fever

During 2024, reference laboratories in Brazil documented an increase of OROV detection through molecular assays. By July 2024, over 1,400 confirmed cases were recorded from areas outside of endemic regions. A genomics analysis was conducted to examine the genetic relationship of recent clinical samples and to understand how cases have been exported from North Brazil to other regions. The WHO PAHO released interim guidance for public health authorities focusing particularly on vector surveillance, vector control and serological surveillance of humans and wild animals.

4. Novel pathogens and diseases

4.1 Novel zoonotic bat-derived poxvirus

During May 2023, a patient was admitted to the Sourasky Medical Centre in Tel Aviv, Israel, with multiple pox-like skin lesions, fatigue, general malaise, myalgia, excessive sweating, watery diarrhoea and a sore throat. The skin lesions later became pustular, sensitive, and painful to touch and were localized to the patient’s hand. Molecular testing through biopsies and swab specimens returned negative results for mpox, herpes simplex and varicella zoster. A subsequent case study reported that the patient was infected with a bat-derived poxvirus, IsrRAPXV. The case reported being bitten and scratched whilst caring for sick bats. At least 4 unconfirmed cases were reported in the patient’s colleagues that were also caring for sick bats but did not seek medical attention.

5. Further reading

Effectiveness of rVSV-ZEBOV vaccination during the 2018–20 Ebola virus disease epidemic in the Democratic Republic of the Congo: a retrospective test-negative study

Global and regional mortality statistics of Nipah virus from 1994 to 2023: a comprehensive systematic review and meta-analysis

Highly Pathogenic Avian Influenza Virus H5N1 clade 2.3.4.4b in Wild Rats in Egypt during 2023

Limitations of mpox lateral flow tests in assessing orthopoxvirus immunity

Mayaro Virus: An Emerging Alphavirus in the Americas

Preprint (Non peer-reviewed) Evaluation of Coinfection and Superinfection Impact on Chikungunya and Mayaro Virus’s Replication in Aedes aegypti

Preprint (non-peer reviewed): First Report of Nipah virus shed in urine by fruit bats (Pteropus medius), Sri Lanka

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

7. Authors of this report

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

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