This week’s update highlights the rising measles outbreak in the United States, new evidence of mammal-to-mammal transmission of avian influenza, and expert warnings on H5N1 pandemic preparedness. We also cover a mysterious disease outbreak in the Democratic Republic of the Congo, the first foot-and-mouth disease detection in Hungary in over 50 years, and the UK’s investigation into a Lassa fever case. These developments underscore the urgent need for strengthened One Health strategies, global surveillance, and pandemic preparedness efforts.
Measles Outbreak Update: Texas Leads US Cases, CDC Reports 164 Nationwide with One Death
The Centers for Disease Control and Prevention (CDC) has reported a sharp rise in measles cases across the United States, with 164 confirmed infections and two deaths as of February 27, 2025. Texas accounts for the majority (140 cases), followed by New Mexico, California, Georgia, New Jersey, Alaska, New York City, Kentucky, and Rhode Island. Notably, 93% of cases stem from outbreaks involving three or more related infections, particularly in Texas, New Mexico, and New Jersey. Since the last update, 71 new cases have been identified, with the highest impact among children and adolescents aged 5-19 years (48%) and children under 5 years (34%). The CDC’s epidemiological data indicate that 95% of cases involve unvaccinated individuals or those with unknown vaccination statuses, and 20% of infections required hospitalization. In response, the CDC has issued a Level 1 travel advisory for international travelers, urging them to stay updated on measles vaccination protocols. The New York State Department of Health has also released a health advisory on heightened measles risks amid the ongoing outbreak. This surge follows a record-high 285 measles cases in 2024, marking the largest U.S. outbreak since 2019—with similar trends of low vaccination coverage and hospitalization risks. Public health experts emphasize immediate vaccination efforts to contain further
Source: CDC
Bird Flu, Avian Influenza H5N1: Expanding Transmission in Livestock and Global Concerns
The highly pathogenic avian influenza (H5N1) outbreak continues to spread, raising concerns over its potential adaptation to mammals. As of March 5, 2025, 980 confirmed cases in livestock herds have been reported across 18 U.S. states, while 1,622 detections in poultry flocks have occurred in all 50 states and Puerto Rico. Recent studies indicate H5N1 transmission in dairy cattle and pigs, highlighting its ability to infect multiple mammalian species.
Globally, avian influenza surveillance is intensifying, particularly as new mammalian infections raise pandemic preparedness concerns. The CDC has confirmed 70 human H5N1 cases in the U.S. since 2024, primarily linked to livestock and poultry exposure, with one fatality reported. While no evidence of sustained human-to-human transmission has been detected, experts warn that the virus’s continued spread in mammals could increase its potential for genetic reassortment, heightening the risk of a future pandemic.
The CDC and USDA continue monitoring H5N1 in both animal and human populations, while researchers emphasize the need for enhanced biosecurity measures, improved surveillance, and accelerated vaccine development for both livestock and humans.
Sudan Virus Outbreak in Uganda: 14 Cases, 4 Deaths
Uganda has reported 14 cases (12 confirmed, 2 probable) and 4 deaths of Sudan virus disease (SVD) since the outbreak was declared on January 30, 2025. The latest case, a child under five, died at Mulago Hospital, with two additional cases and two probable deaths linked to this case. The outbreak has spread across six districts, including Kampala and Jinja, with 192 contacts under monitoring. With no licensed vaccines or treatments, health officials warn of a high public health risk.
Source: WHO
Mpox Remains a Global Health Threat: Over 25,000 Cases and Ongoing International Spread
The mpox outbreak in Africa, first declared a public health emergency of international concern by WHO in August 2024, continues to pose a significant threat, with 25,171 confirmed cases and 83 deaths reported across 22 African countries as of March 2, 2025. The Democratic Republic of the Congo (DRC) remains the epicenter, accounting for 68.9% of cases, while Burundi (14.2%) and Uganda (13.5%) have also seen substantial increases. A large number of suspected cases and additional deaths remain under investigation, particularly in the DRC.
Beyond Africa, Clade I mpox cases have been detected globally, with new imported infections reported in Belgium, France, Qatar, and the United Kingdom. All imported cases had travel history to African regions with ongoing transmission or the United Arab Emirates (UAE). The WHO continues to emphasize enhanced surveillance, rapid case detection, and international coordination to curb further
Source: WHO
Mysterious Disease Outbreak in DRC: 1,318 Cases, 53 Deaths Under Investigation
Health authorities in the Democratic Republic of the Congo (DRC) are investigating a mystery disease outbreak affecting the Basankusu and Bolomba Health Zones in Equateur Province. As of February 25, 2025, a total of 1,318 suspected cases and 53 deaths have been reported in Basankusu, while a separate cluster in Bolomba recorded 12 cases and 8 deaths (fatality rate: 66.7%).
The cause of the outbreak remains unknown, though laboratory tests have ruled out Ebola and Marburg viruses. Initial findings suggest that severe malaria, bacterial meningitis, or chemical poisoning may be contributing factors. Notably, cases in Basankusu have disproportionately affected young adult males, prompting further investigation into possible environmental or occupational exposures.
While recent case numbers appear to be declining, WHO officials caution that the outbreak may not be fully contained. Ongoing epidemiological and laboratory analyses aim to identify the definitive cause and implement targeted response measures.
Source: NGS article
Lassa Fever Case in the UK: Authorities Trace Contacts, Public Risk Remains Low
UK health authorities are actively tracing contacts of a confirmed Lassa fever case after a traveler to England, who has since returned to Nigeria, tested positive for the virus. While Lassa fever is endemic in parts of West Africa, it remains rare in the UK, with only a few previous cases, the most recent in 2022.
The UK Health Security Agency (UKHSA) reassures the public that Lassa fever does not spread easily between people, and the overall risk to the UK population is very low. The virus is typically transmitted through food or household items contaminated with rat urine or feces in endemic regions.
Health protection teams are working at speed to identify and contact anyone who may have been exposed while the individual was in England. Those at risk will be monitored and advised to seek medical care and testing if symptoms develop.
Currently, there is no single effective treatment for Lassa fever, but supportive care—including fluid management and symptom-based treatment—is provided to infected individuals. Authorities remain confident in their ability to identify and contain cases quickly to limit further spread
Source: BBC Health
First Foot-and-Mouth Disease in Hungary in 50 Years Sparks UK & Czech Trade Bans
Hungary has reported its first case of foot-and-mouth disease (FMD) in over five decades, detected at a cattle farm near the Slovak border, according to the World Organisation for Animal Health (WOAH). While FMD poses no risk to humans, it is highly contagious among cloven-hoofed animals, including cattle, pigs, sheep, and goats, leading to severe economic losses and trade restrictions.
In response, the United Kingdom has banned meat and dairy imports from Hungary and Slovakia, covering livestock and untreated animal products, effective immediately. Additionally, travelers will no longer be allowed to bring meat, dairy, and animal by-products from the affected countries into Britain.
The Czech Republic has also announced strict preventive measures, including a ban on transporting susceptible animals from Hungary and Slovakia, except for direct-to-slaughter shipments. Czech authorities will begin border inspections on Tuesday, and farms must disinfect vehicles and restrict entry for individuals who have recently visited Hungary.
This outbreak follows a recent suspected FMD case in Germany, raising concerns over regional virus transmission. Officials across Central Europe continue to monitor the situation closely and implement containment measures.
Source: Politico
Possible Mammal-to-Mammal Transmission of Bird Flu
A new study published in Nature Communications has provided compelling genetic evidence suggesting that the H5N1 avian influenza virus may spread between mammals. The research analyzed virus samples from the 2022-2023 avian influenza outbreak in Chile, identifying a rare genetic mutation shared between human and marine mammal cases. Phylogenetic clustering of these viral strains suggests that mammalian transmission may have occurred, raising concerns about the virus’s ability to evolve toward increased zoonotic transmission. However, researchers caution that further studies are required to confirm the full scope of H5N1 mammalian adaptation. These findings underscore the importance of enhanced surveillance in livestock and wildlife populations to mitigate potential spillover risks to humans.
Source: Nature Communication
Experts Urge Immediate Pandemic Preparedness as H5N1 Spreads Across Species
In an open letter published in Science, leading pandemic response experts, including representatives from the Coalition for Epidemic Preparedness Innovations (CEPI) and Georgetown University, have issued a stark warning on the escalating threat of H5N1 avian influenza. The letter emphasizes the rapid cross-species transmission of H5N1, including recent detections in dairy cattle and humans in the United States. Experts highlight the urgent need for global pandemic preparedness measures, citing the limitations of current vaccine production technologies, outdated regulatory processes, and gaps in international outbreak response frameworks. The authors urge policymakers to accelerate scalable pandemic flu vaccine development, enhance global public health communication to combat misinformation, and establish transparent emergency response mechanisms. Given the virus’s expanding host range, experts stress that proactive mitigation strategies are crucial to minimize economic disruptions, protect public health, and prevent large-scale human outbreaks.
Source: Letter to Science, authored by Dr. Nicole Lurie et al.2025
Bovine-Derived H5N1 Infects Pigs, But Doesn’t Spread Among Them
A preprint study published on bioRxiv has demonstrated that pigs can become infected with the bovine-derived H5N1 avian influenza virus, but do not readily transmit the virus to other pigs. In the study, researchers experimentally inoculated piglets with the H5N1 B3.13 strain, finding evidence of viral replication in respiratory tissues and limited adaptation to mammalian hosts. Some genetic mutations associated with mammalian adaptation were detected, yet there was no significant viral transmission to sentinel pigs housed in the same environment. These findings suggest that while pigs may serve as potential hosts for bovine-origin H5N1, the virus does not currently exhibit efficient pig-to-pig transmission. However, researchers emphasize the critical role of pigs as “mixing vessels” for influenza viruses, which can facilitate genetic reassortment and increase pandemic risks. Enhanced surveillance in livestock populations is essential to monitor viral evolution and mitigate future spillover threats.
Source: CIDRAP
One Health Briefs provides weekly updates based on publicly available data from reputable health organizations, including WHO, CDC, and national health agencies. Information is subject to change as new data emerges. For the most accurate and up-to-date details, refer directly to official sources.
