Kiplagat SJ, Rodriguez DM, Rivera A
… +3 more, Paz-Bailey G, Wong JM, Adams LE
MMWR Morb Mortal Wkly Rep
· 2026 May · PMID 42133551
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Dengue is a mosquitoborne viral disease that can cause mild to severe illness and death. During 2010-2023, an average of 828 dengue cases (range = 202-2,055) were reported annually to ArboNET, the national arboviral surv...Dengue is a mosquitoborne viral disease that can cause mild to severe illness and death. During 2010-2023, an average of 828 dengue cases (range = 202-2,055) were reported annually to ArboNET, the national arboviral surveillance system for the 50 U.S. states and the District of Columbia. During 2024, a record 3,798 dengue cases were reported, representing a 359% increase above the 2010-2023 annual average. Among these 3,798 cases, 97.2% were associated with travel outside the reporting jurisdiction during the 2 weeks preceding symptom onset; the remaining 2.8% were locally acquired. The number of dengue cases peaked during July-September (accounting for 41.6% of total annual cases), with the highest percentage (21.8%) of cases occurring among persons aged 50-59 years. Among travel-associated cases, acquisition occurred primarily in the Caribbean (including Puerto Rico and the U.S. Virgin Islands) (34.1%), North America (Mexico and the United States) (24.3%), and Central America (15.6%); Hispanic or Latino persons accounted for 57.5% of all cases. Among all patients, 36.1% required hospitalization, 2.8% of cases were severe, and six (0.2%) patients died. Among 1,204 patients with known dengue virus (DENV) serotype, DENV-3 was the most commonly reported (54.8%) among the four DENV serotypes. These findings underscore the urgent need for enhanced prevention strategies, clinical awareness, and tailored public health messaging for travelers to areas where dengue is endemic.
Kibiger L, Oltean HN, Leitz L
… +49 more, Krause E, Barrett D, Halloran A, Yomogida K, Lipton B, Paris K, Keirn J, Buswell M, Black A, Trinh P, Murray T, Bonaccorso R, Banuelos L, Dieringer E, Lenahan J, Davizon ES, Marder EP, Mullins J, Kay M, Chow EJ, Valenciano SJ, Lynch J, Makarewicz V, Bryson-Cahn C, Hernandez J, Haggith K, Linn V, Greninger AL, Goya S, Gulla S, Young J, Kerns-Funk S, da Silva Bhatia B, Bruce H, Kniss K, Reinhart K, Ohlstein R, Johnson S, Schofield C, Smith P, Itle A, Gibson M, Torrevillas B, Falghoush A, Waltzek TB, Snekvik K, Torchetti M, Uyeki TM, Lindquist S
MMWR Morb Mortal Wkly Rep
· 2026 May · PMID 42096351
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Clade 2.3.4.4b influenza A(H5N1) viruses have circulated across migratory bird flyways in the United States since 2022, including in Washington, where backyard flock detections have been reported annually. In November 20...Clade 2.3.4.4b influenza A(H5N1) viruses have circulated across migratory bird flyways in the United States since 2022, including in Washington, where backyard flock detections have been reported annually. In November 2025, a Washington resident died from acute respiratory failure after receiving a positive influenza A(H5) test result at a hospital laboratory. Washington Public Health Laboratories confirmed influenza A(H5), and genomic sequencing identified influenza A(H5N5) virus (A6 genotype). Polymerase chain reaction testing detected highly pathogenic avian influenza A(H5) virus clade 2.3.4.4b from an apparently healthy backyard flock of ducks and sediment from a watering basin on the patient's property. Six of eight gene segments from the environmental sample and one duck sample (partial neuraminidase segment) were highly genetically similar to the patient's virus sequence. Although existing wild bird surveillance had not detected influenza A(H5N5) virus (A6) in the U.S. Pacific Flyway, introduction via wild birds into the environment of the backyard flock was likely the source of the patient's exposure. The public health investigation identified approximately 135 exposed persons; symptom monitoring and influenza testing detected no additional cases. The overall risk for avian influenza A remains low among the general U.S. population; however, novel avian influenza A virus infection should be considered in persons with symptoms of influenza and potential exposures.
Vaughan A, Joyce A, Traub E
… +21 more, Jae M, Beeler E, Paiva E, Ananian K, Holiday C, Jefferson S, Richardson J, Munna C, Chan C, Scott T, Kojima N, Seneviratne T, Mellis A, Olsen SJ, Green N, Feaster M, Terashita D, Balter S, Levine MZ, Middleton J, de St Maurice A
MMWR Morb Mortal Wkly Rep
· 2026 May · PMID 42096344
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Since 2021, avian influenza A(H5N1) clade 2.3.4.4b viruses have spread widely among wild birds and domesticated poultry in the United States, with sporadic spillover into mammals. During November 2024-January 2025, 19 do...Since 2021, avian influenza A(H5N1) clade 2.3.4.4b viruses have spread widely among wild birds and domesticated poultry in the United States, with sporadic spillover into mammals. During November 2024-January 2025, 19 domestic cats in Los Angeles County, California, became ill after consumption of commercially purchased raw milk, raw meat, or raw pet food; nine cats tested positive for influenza A(H5N1) virus (clade 2.3.4.4b genotype B3.13). Overall, 139 persons were exposed to the 19 infected cats, and all were monitored for symptoms. Although 30 persons reported influenza-like illness symptoms, none received a positive influenza A(H5) reverse transcription-polymerase chain reaction (RT-PCR) test result. In April 2025, the Los Angeles County Department of Public Health and CDC invited all exposed persons to participate in an influenza A(H5N1) serosurvey to determine whether transmission of influenza A(H5N1) virus occurred, including in those without symptoms. Sera from 25 (18%) of the 139 exposed persons were tested. Among these, antibodies specific to A(H5N1) clade 2.3.4.4.b (antigenically similar to the clade 2.3.4.4.b influenza A[H5N1] virus isolated from the infected cats) were detected in serum from one veterinary professional, who was asymptomatic. This person did not use respiratory or eye protection during the exposure, did not report influenza-like illness after the exposure, and reported no other known risk factors for A(H5N1) infection. These findings represent serologic evidence of possible transmission of influenza A(H5N1) clade 2.3.4.4.b virus from a domestic cat to a human, highlighting concerns about potential cat-to-human transmission of influenza A(H5N1) virus and the importance of infection control practices in veterinary settings.
Raz KM, Haddad MB, Althomsons SP
… +9 more, Cowan L, Kammerer JS, Lam CK, McDaniel CJ, Posey J, Talarico S, Walker WL, Schwartz NG, Wortham JM
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 42060525
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During 2017-2023, based on an analysis of national genomic and tuberculosis (TB) case surveillance data, 50 large TB outbreaks (10 or more related TB cases in a 3-year period) involving 1,092 cases were identified in 23...During 2017-2023, based on an analysis of national genomic and tuberculosis (TB) case surveillance data, 50 large TB outbreaks (10 or more related TB cases in a 3-year period) involving 1,092 cases were identified in 23 states. Compared with 61,993 other persons who received a diagnosis of TB during this period, persons included in large outbreaks were more frequently U.S.-born (79% versus 26%), and a higher percentage reported substance use (27% versus 12%), homelessness (9% versus 5%), and incarceration (11% versus 3%). Approximately one fourth of these large outbreak-related cases were identified through contact tracing; these cases less commonly had clinical markers of highly infectious disease (23%) than did large outbreak-related cases identified through other methods (including evaluation associated with symptoms, targeted testing, or incidental findings) (61%), suggesting that contact tracing might have facilitated earlier diagnosis. Among the 50 large outbreaks, 34 (68%) were primarily associated with family or social networks, and 13 (26%) were primarily associated with congregate settings. Maintaining state and local public health capacity for outbreak detection, prevention, and response is essential, even in low-incidence jurisdictions. Effective outbreak responses must overcome barriers to diagnosis and treatment associated with homelessness and substance use and include efforts to build trust with affected communities. Procedures to promptly identify and isolate persons with infectious TB remain critical in congregate settings.
Strelau KM, Pareles E, Kelso P
… +10 more, Matusevich C, Casey P, Doncaster E, Levine K, Gould CV, Staples JE, Fitzpatrick KA, Burkhalter KL, Connelly CR, Kwit NA
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 42060520
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Eastern equine encephalitis (EEE) virus (EEEV) is a mosquitoborne alphavirus maintained in an enzootic cycle with mosquitoes and birds. EEEV can be transmitted to humans and susceptible animals by mosquitoes that bite bo...Eastern equine encephalitis (EEE) virus (EEEV) is a mosquitoborne alphavirus maintained in an enzootic cycle with mosquitoes and birds. EEEV can be transmitted to humans and susceptible animals by mosquitoes that bite both mammals and birds. EEEV causes severe neuroinvasive disease in humans; although an EEE vaccine is available for horses, no human vaccine is currently licensed, and treatment is supportive. Approximately one third of human cases are fatal, and many survivors experience long-term neurologic sequelae (1). In the United States, a majority of EEE cases occur in states along the Atlantic Coast, Gulf Coast, and Great Lakes. EEEV was first detected in Vermont during a 2010 serosurvey of hunter-harvested deer and moose (2,3). After a 2011 outbreak of EEEV on a Vermont emu farm (4), statewide mosquito surveillance for EEEV was implemented in 2012. During 2012-2022, two human and four animal EEE cases were reported to the Vermont Department of Health (VDH). During 2023-2024, EEEV activity in mammals and mosquitoes increased, prompting targeted outreach in affected areas. This report describes EEEV activity in Vermont during 2023-2024 based on human and equine cases and mosquito surveillance data.
Robles RL, Gertz AM, Alvarado-Ramy F
… +11 more, Asare A, Pringle K, Adams K, Hercules Y, Brown MG, King J, Pimentel LC, Minhaj FS, Brown C, Mase S, Gearhart S
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 42024631
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Monkeypox is a vesicular rash illness caused by Monkeypox virus (MPXV), which can be divided into clades (e.g., clade I and II), each of which includes subclades. MPXV is usually transmitted from person to person through...Monkeypox is a vesicular rash illness caused by Monkeypox virus (MPXV), which can be divided into clades (e.g., clade I and II), each of which includes subclades. MPXV is usually transmitted from person to person through close, sustained physical contact. Global spread of clade II MPXV began in 2022; to date, approximately 37,500 cases have been reported in the United States (provisional data), and domestic transmission is ongoing. CDC began conducting aircraft contact investigations for clade II MPXV in 2021. In February 2023, based on data showing no evidence of in-flight transmission of clade II MPXV, CDC discontinued routine aircraft contact investigations. Although outcome data were missing for approximately one third of identified aircraft contacts, a 2024 report describing data from 2021 to 2022 on clade II MPXV transmission risk during commercial air travel found no secondary cases reported among 1,538 persons who had contact with 113 infected travelers on 221 flights (1).
Bell JM, Barbre K, Meng L
… +12 more, Lape-Newman B, Wong E, Woods A, Kalayil EJ, Dubendris H, Prosper MS, Edwards J, Soe MM, Kuhar DT, Stuckey MJ, Lindley MC, Benin A
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 42024628
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Nursing home residents and health care personnel (HCP) are at increased risk for exposure to influenza; in addition, residents of nursing homes who acquire influenza are at increased risk for severe disease. The Advisory...Nursing home residents and health care personnel (HCP) are at increased risk for exposure to influenza; in addition, residents of nursing homes who acquire influenza are at increased risk for severe disease. The Advisory Committee on Immunization Practices recommends routine annual seasonal influenza vaccination for persons without contraindications, including HCP and those at increased risk for severe influenza. Nursing homes report influenza vaccination among residents and HCP to CDC's National Healthcare Safety Network. This report describes influenza vaccination coverage among nursing home residents and HCP working in nursing homes during the 2024-25 influenza season (October 1, 2024-March 31, 2025). At the end of the 2024-25 influenza season, influenza vaccination coverage was 61.3% among nursing home residents and 42.1% among HCP who work in nursing homes; coverage among HCP varied by employment type. This study is the first comprehensive, national assessment of influenza vaccination coverage among nursing home residents and HCP who work in nursing homes in the United States. Monitoring of influenza vaccination coverage in this population at high risk for influenza exposure and severe influenza disease, along with implementation of a combination of influenza vaccination, administration of influenza antiviral medications, and other recommended practices to control the spread and severity of influenza in nursing home settings, can help protect nursing home residents and HCP against severe influenza-associated outcomes.
Rumph JT, Winquist A, Troeschel AN
… +14 more, Pulver S, Schnall AH, Ebersole J, Yeh M, Burt B, Federman SL, Klontz K, Dasenbrock C, Leahy HL, Brady S, Stuteville H, Patel K, Daniel J, Chang A
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 41955162
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In late spring 2024, CDC was alerted to an outbreak of poisoning potentially associated with eating Diamond Shruumz microdosing chocolate bars. Diamond Shruumz microdosing chocolate bars are edible products designed so t...In late spring 2024, CDC was alerted to an outbreak of poisoning potentially associated with eating Diamond Shruumz microdosing chocolate bars. Diamond Shruumz microdosing chocolate bars are edible products designed so that small doses of mushroom-derived psychoactive compounds and other psychoactive ingredients can be eaten in a presectioned serving. In response to this alert, CDC and the Food and Drug Administration coordinated a nationwide outbreak investigation to characterize the potential poisonings associated with eating Diamond Shruumz microdosing chocolate bars. A case of poisoning was defined as an illness with moderate or major clinical effects (i.e., symptoms) as defined by America's Poison Centers in a person who ate any Diamond Shruumz product or another mushroom-containing chocolate product during January-October 2024. In total, 180 cases were reported in 34 states. Among these, 73 persons were hospitalized, including 38 persons who required intensive care unit (ICU) admission, 29 who required endotracheal intubation, and two deaths. Eating Diamond Shruumz chocolate bars was associated with higher odds of hospitalization (odds ratio [OR] = 3.29; 95% CI = 1.51-7.40), ICU admission (OR = 6.30; 95% CI = 2.17-22.6), seizures (OR = 8.45; 95% CI = 3.00-27.9), and endotracheal intubation (OR = 8.04; 95% CI = 2.24-44.2), compared with eating other mushroom-containing chocolate products. Eating larger amounts of Diamond Shruumz chocolate bars was associated with an increased likelihood of hospitalization, ICU admission, and endotracheal intubation (p-value for trend tests [p-trend] = 0.023, 0.004, and <0.001, respectively). Diamond Shruumz products were recalled, and the public was advised not to eat, sell, or serve any Diamond Shruumz products and to discard any Diamond Shruumz products previously purchased. Testing of some Diamond Shruumz products identified substances present in psychoactive mushrooms, including muscimol, psilocin (a Schedule I controlled substance), kavalactones, and other substances in some, but not all, tested products. Consumers should be aware of the poisoning risk associated with eating Diamond Shruumz products and other mushroom-containing microdosing chocolate products due to variability in ingredient composition, the absence of standardized regulatory oversight for sampling and testing finished products, and the potential toxicity of compounds intended to produce psychoactive effects.
Logan N, Birhane MG, McDonald SL
… +26 more, Alarcón J, Amador S, Anand M, Bachmann LH, Bernard K, Black LS, Chen AN, Cooley LA, Fortes ED, Gerard M, Jervis RH, Kimura AC, Lamba K, Latash J, Li L, Pederson G, Kauffman CP, Reynolds JL, Santiago R, Siemetzki-Kapoor U, Smole SC, Tagg KA, Vostok J, Webb HE, Francois Watkins LK, XDR Shigella Working Group
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 41955161
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Shigellosis is a nationally notifiable diarrheal illness caused by gram-negative bacteria. Shigella infection is spread through fecal-oral transmission and sexual contact. Although most infections are self-limited, antib...Shigellosis is a nationally notifiable diarrheal illness caused by gram-negative bacteria. Shigella infection is spread through fecal-oral transmission and sexual contact. Although most infections are self-limited, antibiotics are indicated for severe illness or to reduce transmission in settings with high risk for spread. Since 2015, a growing proportion of cases has been caused by extensively drug-resistant (XDR) Shigella species, defined as being resistant to ampicillin, azithromycin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole. No Food and Drug Administration-approved oral antimicrobial agents are available to treat these XDR infections. To describe U.S. trends and epidemiologic characteristics of XDR shigellosis, CDC analyzed Shigella isolates submitted to PulseNet, CDC's molecular surveillance network for enteric pathogens, during January 1, 2011-October 20, 2023; antimicrobial resistance was characterized using whole-genome sequencing data and antimicrobial susceptibility testing. Among 16,788 isolates with resistance data during this period, 510 (3.0%) were XDR. The percentage of XDR isolates increased from 0% during 2011-2015 to 8.5% in 2023. Species information was available for 505 (99%) of 510 XDR isolates; among those, 333 (65.9%) were Shigella sonnei and 172 (34.1%) were Shigella flexneri. Among patients with XDR shigellosis, the median patient age was 41 years (IQR = 31-54 years) and 86.2% were men. Among patients with available travel history, 76.2% (173 of 227) reported no recent domestic travel and 82.4% (169 of 205) reported no recent international travel. Among 116 persons with available HIV status, 54 (46.6%) reported HIV co-infection. Strengthened surveillance, timely reporting, and targeted prevention strategies are needed to limit transmission of XDR Shigella strains.
Towers EB, Williams IL, Holstege CP
… +1 more, Farah R
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 41926333
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Kava (Piper methysticum), a central nervous system depressant derived from a plant in the pepper family native to the Pacific Islands, is traditionally consumed in religious, cultural, political, and social ceremonies. I...Kava (Piper methysticum), a central nervous system depressant derived from a plant in the pepper family native to the Pacific Islands, is traditionally consumed in religious, cultural, political, and social ceremonies. In the United States, kava emerged in the late 1990s and has experienced renewed growth and product diversification since the 2010s, with increasing availability of concentrated extracts and ready-to-drink beverages. These commercial products are commonly marketed as healthy alternatives to alcohol, sold near college campuses, and increasingly being combined with kratom, a psychoactive botanical with opioid-like effects, raising safety concerns. Data on kava-related use during January 2000-December 2025 that resulted in a report to the National Poison Data System (i.e., kava exposure report) were analyzed to assess trends by users' demographic characteristics, exposure type, and outcomes. Kava-related exposure reports declined sharply after a 2002 Food and Drug Administration advisory on kava-associated severe liver injury but have risen steadily since 2011, reaching 203 reported exposures in 2025. Reports primarily involved adults aged ≥20 years, but demographic characteristics have changed over time. During 2000-2001, reports primarily involved females and included more children aged ≤12 years, whereas exposure reports since 2013 have predominantly involved men; reports involving children have been rare. Since 2017, reports involving combined use of kava and kratom have increased, reaching 30% (61) of all kava reports in 2025. These increases have coincided with higher rates of serious reported clinical outcomes in recent years (32% in 2025 compared with 12% in 2000). These data indicate a resurgence of overall kava exposure reports to poison centers, as well as an increase in kratom-related kava reports, which has coincided with higher rates of serious clinical outcomes. The findings in this report suggest the need for enhanced surveillance for, clinical awareness of, and public education regarding commercial products containing kava.
Meghani M, Garacci Z, Razzaghi H
… +4 more, de Perio MA, Laney AS, Kriss JL, Black CL
MMWR Morb Mortal Wkly Rep
· 2026 Apr · PMID 41926326
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The Advisory Committee on Immunization Practices (ACIP) recommends that all health care personnel (HCP) receive an annual influenza vaccination to reduce the risk for influenza and influenza-related morbidity and mortali...The Advisory Committee on Immunization Practices (ACIP) recommends that all health care personnel (HCP) receive an annual influenza vaccination to reduce the risk for influenza and influenza-related morbidity and mortality among themselves and their patients. For the 2024-25 respiratory virus season, ACIP also recommended that all HCP be vaccinated against COVID-19. During March 26-April 17, 2025, CDC conducted a nonprobability opt-in internet panel survey of 2,650 U.S. HCP to estimate influenza and COVID-19 vaccination coverage during the 2024-25 respiratory virus season. Overall, 76.3% of HCP reported having received an influenza vaccine and 40.2% reported receiving the 2024-25 COVID-19 vaccine. Influenza vaccination coverage was highest among pharmacists (94.6%), physicians (92.6%), and HCP who worked in hospital settings (88.3%). COVID-19 vaccination coverage was highest among physicians (46.7%), assistants or aides (46.7%), and HCP who worked in long-term care and home health care settings (44.5%). Both influenza and COVID-19 vaccination coverage rates were highest among HCP whose employer required or recommended the vaccines or offered them on-site. A multipronged approach, including educating HCP about benefits of vaccination and implementing workplace strategies (such as employer vaccination recommendations or offering on-site vaccination) might improve vaccination coverage and reduce influenza- and COVID-19-related morbidity among HCP.
Towers EB, Thomas YT, Holstege CP
… +1 more, Farah R
MMWR Morb Mortal Wkly Rep
· 2026 Mar · PMID 41886310
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Kratom, the leaves of a tropical evergreen tree (Mitragyna speciosa), is traditionally consumed in Southeast Asia for pain relief, mood enhancement, and to relieve symptoms of opioid withdrawal. Kratom contains psychoact...Kratom, the leaves of a tropical evergreen tree (Mitragyna speciosa), is traditionally consumed in Southeast Asia for pain relief, mood enhancement, and to relieve symptoms of opioid withdrawal. Kratom contains psychoactive compounds that interact with opioid receptors and is widely available in various forms in the United States. Its evolution from natural leaf to high-potency alkaloid products has raised concerns about toxicity. Data on kratom-related use that resulted in a report to the National Poison Data System (NPDS) (i.e., kratom exposure report) during 2015-2025 were analyzed to assess trends by exposure report type, demographic characteristics of persons exposed, and outcomes. During the past 11 years, poison centers received a total of 14,449 kratom exposure reports; the record high 3,434 reports in 2025 represent an increase of approximately 1,200% compared with the 258 reports in 2015. Most reports involved males and young adults aged 20-39 years, but reports among adults aged 40-59 years increased most sharply, with rates nearly overlapping with those among young adults by 2025. Although single-substance exposure reports accounted for most reports (62%), multiple-substance reports occurred at higher rates (range = 467-5,442 per 1 million multiple-substance drug exposure reports versus 388-4,045 per 1 million single-substance drug exposure reports), were associated with more hospitalizations (44%-56% versus 24%-29% annually) and serious (life threatening, pronounced, prolonged, or systemic) outcomes (57%-66% versus 41%-49% annually), and accounted for the vast majority of kratom-associated deaths during the study period (184 of 233; 79%). NPDS data indicate that kratom-related reports to poison centers are increasing and expanding among demographic groups, underscoring the value of ongoing surveillance to identify high-risk patterns of kratom use and guide strategies to reduce risks from multiple-substance exposure reports.
Hill HA, Yankey D, Elam-Evans LD
… +5 more, Mu Y, Chen M, Stokley S, Peacock G, Singleton JA
MMWR Morb Mortal Wkly Rep
· 2026 Mar · PMID 41886308
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The National Immunization Survey-Child monitors coverage with recommended routine childhood vaccines. For data collected in survey year 2024, which include children born in 2021 and 2022, the household response rate (23....The National Immunization Survey-Child monitors coverage with recommended routine childhood vaccines. For data collected in survey year 2024, which include children born in 2021 and 2022, the household response rate (23.4%) and availability of adequate provider data for children with completed interviews (51.4%) were comparable to those from earlier survey years. For most vaccines, coverage by age 24 months was similar among children born in 2021 and 2022 and those born in 2019 and 2020. Declines in coverage of 1-2 percentage points were observed for the primary series of Haemophilus influenzae type b conjugate vaccine, the birth dose of hepatitis B vaccine, ≥4 doses of pneumococcal conjugate vaccine, and rotavirus vaccine. Coverage with ≥2 doses of influenza vaccine by age 24 months decreased from 61.0% among children born during 2019-2020 to 53.5% among those born during 2021-2022. Coverage was lower among Vaccines for Children (VFC) program-eligible children than among those who were not VFC-eligible and differed substantially by jurisdiction. Compared with non-Hispanic White children, coverage with many vaccines was lower among non-Hispanic Black or African American and Hispanic or Latino children; coverage was highest among non-Hispanic Asian children. Coverage was also lower among children living in poverty and those living in more rural areas. Maintaining high levels of vaccination and improving coverage among groups and in areas in which rates have declined could help protect children from vaccine-preventable morbidity and mortality. The Community Preventive Services Task Force recommends several interventions to increase vaccination, including standing orders for vaccination, immunization information systems, and vaccination programs in organized child care centers and in Special Supplemental Nutrition Program for Woman, Infants, and Children settings. Other factors demonstrated to be effective include strong provider recommendations, targeted messages from credible and trusted sources, and increased participation in the VFC program.
Shakya M, Ma KC, Hughes LJ
… +20 more, Smith C, Atherton LJ, Boehm AB, Cook PW, Cornforth DM, Gardner M, Goraichuk IV, Harcourt JL, Hicks H, Johnson M, Kelleher A, Reese HE, Sabin SJ, Smith TC, Tamin A, Wolfe MK, Silk BJ, Paden CR, Thornburg N, MacNeil A
MMWR Morb Mortal Wkly Rep
· 2026 Mar · PMID 41855090
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The SARS-CoV-2 variant BA.3.2 was first identified in South Africa on November 22, 2024. BA.3.2 has approximately 70-75 substitutions and deletions in the gene sequence of the spike protein relative to JN.1 and its desce...The SARS-CoV-2 variant BA.3.2 was first identified in South Africa on November 22, 2024. BA.3.2 has approximately 70-75 substitutions and deletions in the gene sequence of the spike protein relative to JN.1 and its descendant, LP.8.1, the antigens used in the 2025-26 COVID-19 vaccines. CDC is using a multimodal SARS-CoV-2 genomic surveillance approach to monitor the emergence and spread of BA.3.2 and other SARS-CoV-2 variants internationally and within the United States. The first U.S. BA.3.2 detection occurred on June 27, 2025, through CDC's Traveler-Based Genomic Surveillance program in a participant traveling to the United States from the Netherlands. The first U.S. detection of BA.3.2 in a clinical specimen collected from a patient was reported on January 5, 2026. As of February 11, 2026, BA.3.2 had been detected in voluntarily self-collected nasal swabs from four U.S. travelers, clinical samples from five patients, three airplane wastewater samples, and 132 wastewater surveillance samples from 25 states. BA.3.2 has been reported by at least 23 countries. SARS-CoV-2 continues to cause substantial morbidity and mortality worldwide. BA.3.2 mutations in the spike protein have the potential to reduce protection from a previous infection or vaccination. Continued genomic surveillance is needed to track SARS-CoV-2 evolution and determine its potential effect on public health.
Maloney P, Reeves EL, Wielgosz K
… +42 more, Price AM, Natarajan K, DeSilva MB, Dascomb K, Klein NP, Tartof SY, Irving SA, Grannis SJ, Ong TC, Weber ZA, Schuster JE, Zerr DM, Michaels MG, Boom JA, Halasa NB, Staat MA, Weinberg GA, House SL, Saade EA, Geffel KM, Gaglani M, Wernli KJ, Murugan V, Martin ET, Bontrager NAB, Kirby MK, Payne AB, Dawood FS, Tannis A, Moline HL, Zhao SK, Adams K, DeCuir J, Olson SM, Chung JR, Lewis N, Flannery B, Reed C, Garg S, Ellington S, CDC Influenza Vaccine Effectiveness Collaborators, CDC Influenza Vaccine Effectiveness Collaborators
MMWR Morb Mortal Wkly Rep
· 2026 Mar · PMID 41818161
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In the United States, annual influenza vaccination has been recommended for all persons aged ≥6 months, including during the 2025-26 season. Interim influenza vaccine effectiveness (VE) estimates were calculated for pati...In the United States, annual influenza vaccination has been recommended for all persons aged ≥6 months, including during the 2025-26 season. Interim influenza vaccine effectiveness (VE) estimates were calculated for patients with acute respiratory illness-associated outpatient visits and hospitalizations from three U.S. respiratory virus VE networks during the 2025-26 influenza season, using a test-negative case-control design. Among children and adolescents aged <18 years, VE was 38%-41% against influenza outpatient visits and 41% against influenza-associated hospitalization. Among adults aged ≥18 years, VE was 22%-34% against influenza outpatient visits and 30% against influenza-associated hospitalization. Among children and adolescents, VE against influenza A ranged from 37% (against outpatient visits) to 42% (against hospitalization) across settings; among adults, VE against influenza A ranged from 30% (against hospitalization) to 34% (against outpatient visits) across settings. Among children and adolescents, VE against influenza A(H3N2)-associated outpatient visits was 35% and against influenza A(H3N2)-associated hospitalization was 38%. VE against influenza B outpatient visits ranged from 45%-71% among children and adolescents and was 63% among adults. Other estimates of VE were not statistically significant or were not reportable. Although interim influenza VE is lower during the 2025-26 influenza season than it was during recent influenza seasons, these findings demonstrate that influenza vaccination still provides protection against influenza. CDC recommends influenza vaccination; U.S. influenza vaccines remain available for persons aged ≥6 months.
Zhu S, Quint J, León TM
… +9 more, Li NJ, Muldrew S, Porse C, Flannery B, Ellington S, Murray EL, Sachdev D, McCullough K, Schechter R
MMWR Morb Mortal Wkly Rep
· 2026 Mar · PMID 41818142
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Interim estimates of state-level influenza vaccine effectiveness (VE) can help guide timely local public health actions for prevention and treatment of influenza. Linked influenza vaccination and public health influenza...Interim estimates of state-level influenza vaccine effectiveness (VE) can help guide timely local public health actions for prevention and treatment of influenza. Linked influenza vaccination and public health influenza surveillance data from California allowed estimation of interim influenza VE by comparing the odds of seasonal influenza vaccination among persons who received positive and negative influenza test results reported to the California Department of Public Health (CDPH) using a case-control study design. During October 1, 2025-January 31, 2026, a total of 952,765 influenza laboratory test results were reported to CDPH. These data were analyzed, including results for 86,369 (9%) persons with receipt of a positive influenza test result (case-patients) and 866,396 (91%) with receipt of a negative test result (control patients). Overall, 22% of case-patients and 27% of control patients were vaccinated against influenza. Interim VE against any influenza was 33% for all age groups, 39% for children and adolescents aged 6 months-17 years, and 22% for adults aged ≥65 years; VE was 32% against a positive influenza A test result, and 47% against a positive influenza B test result. These results suggest that influenza vaccination was associated with reduced odds for laboratory-confirmed influenza among children and adults. CDPH recommends annual influenza vaccination for all persons aged ≥6 months to reduce the risk for influenza and influenza-associated adverse health outcomes.
Measles is a highly contagious respiratory virus with the potential to cause large outbreaks, as well as serious complications, hospitalization, and death. Receipt of 2 doses of measles vaccine is 97% effective at preven...Measles is a highly contagious respiratory virus with the potential to cause large outbreaks, as well as serious complications, hospitalization, and death. Receipt of 2 doses of measles vaccine is 97% effective at preventing disease and is recommended for all persons aged ≥12 months to ensure high levels of population immunity and reduce the risk for outbreaks. In January 2025, a large measles outbreak began in a west Texas community and quickly spread to nearby jurisdictions, including New Mexico. The New Mexico Department of Health (NMDOH) eventually reported 99 outbreak-related measles cases, approximately one half of which occurred in adults. To facilitate dissemination of information and distribution of resources across a geographically large, rural state, NMDOH implemented a multimodal communication and vaccination outreach strategy, including a centralized webpage, a telephone helpline, and mobile vaccination clinics. The outreach strategy coincided with a statewide 55% increase in MMR vaccine doses administered during January 1-September 26, 2025, compared with the same period in 2024. Coordinating public communication and improving access to MMR vaccine can support vaccine administration across large, rural areas and contribute to a measles outbreak response.