Articles from Emerging Infectious Diseases

Mycobacterium abscessus infections are frequently drug resistant and can cause severe disease, particularly among vulnerable populations in healthcare settings. In June 2024, a cluster of M. abscessus infection cases was reported at a hospital in Maryland, USA. An investigation involving hospital infection prevention staff, the Maryland Department of Health, the Centers for Disease Control and Prevention, and the Wadsworth Laboratory of the New York State Department of Health included initiation of mitigation efforts such as tap water use restrictions, point-of-use water filters, hospitalwide water flushing, and staff education regarding sink safety. Whole-genome sequencing of patient and environmental isolates, coupled with epidemiologic data, revealed a strong association (0–24 single-nucleotide polymorphism differences) between environmental and patient samples, indicating that infections were likely a result of patient exposure to M. abscessus. Ensuring initiation of mitigation initiatives likely prevented additional patient infections. Although effective in this investigation, not all mitigation strategies are equal or sustainable.

Amebic meningoencephalitis (AME) is a highly fatal central nervous system infection caused by various free-living amebae. We describe epidemiology of AME cases from Kerala, India, during January 1–November 11, 2025, and identify behavioral risk factors associated with real-time PCR-confirmed Acanthamoeba spp. infection through a matched case–control study. We identified 159 AME case-patients, of which 67 (42.1%) tested positive for Acanthamoeba spp. amebae. Most AME cases were reported from 4 districts, peaking during the monsoon and postmonsoon periods. Exposure to natural water bodies for swimming or bathing and using nonchlorinated water for domestic purposes were associated with AME. History of maxillofacial injury or nasal surgery with subsequent exposure to natural water bodies and washing ulcers or skin lesions in natural water bodies were associated with higher odds of disease. Targeted risk communication about safe water practices and routine chlorination of domestic water sources could help reduce AME risk in affected communities.

Fleaborne typhus (FBT) is reemerging as a significant cause of febrile illness in southern California, USA. We performed enhanced testing on low-titer Rickettsia typhi antibody–positive specimens from patients with FBT-compatible illness reported in Los Angeles County, California, during 2022–2024. We tested 114 specimens by repeat serology and 113 by real-time PCR; 81 (71%) were PCR-positive, and 95 (83%) had higher antibody titers by repeat serology. Most PCR-positive specimens were collected 8–10 days after illness onset, but some were collected up to 15 days after illness onset. All PCR-positive specimens were R. typhi–specific. After additional testing, 113 (99%) suspected cases were reclassified as probable or confirmed FBT cases. Our findings indicate that many low-titer seropositive results represent true infections and that use of minimum serology thresholds for public health investigation underestimates surveillance case counts. Expanding commercial molecular testing capacity will improve clinical FBT diagnosis and enhance surveillance accuracy.

Cost-effectiveness analyses of tuberculosis (TB) preventive treatment rarely consider long-term TB consequences. We examined how long-term TB consequences influence the effectiveness and cost-effectiveness of TB prevention among persons who immigrate to Canada. By using a Markov microsimulation model of 400,000 persons immigrating to Canada in 2025, we compared current postarrival TB infection screening levels (0.5%) with a screening level of 68% among new immigrants. Modelling scenarios included acute TB consequences and long-term TB-related death, illness, and healthcare costs (25-year horizon, 1.5% discount rate). Including long-term TB-related consequences increased the estimated TB-related quality-adjusted life years (QALYs) lost by 2.1-fold (95% uncertainty range 1.7–2.5-fold). When long-term TB-related consequences were included, estimated QALYs gained from expanded screening increased 2.4-fold (95% uncertainty range 1.6–4.4-fold), reducing the cost per QALY from $235,088 to $100,742 CAD. Ignoring long-term TB consequences substantially underestimates the effectiveness and cost-effectiveness of preventive interventions; such consequences should be incorporated into future evaluations.

We analyzed whole-genome sequencing data for 1,046 human clinical and 1,332 nonclinical Listeria monocytogenes isolates collected across New York, USA, during 2000–2021. Several hypervirulent clonal complexes (CCs) were significantly associated with clinical isolates, and several hypovirulent CCs were associated with nonclinical isolates. Specific CCs also showed association with specific food categories (e.g., processed meat); specific genetic markers (e.g., inlA premature stop codons) were also significantly associated with processed meat isolates. Analysis of clusters that contained food isolates, as well as subsequently identified clinical isolates, showed that time of isolation between food isolates and clinical isolates was significantly shorter for produce isolates than for isolates from meat, dairy, or fish. This finding suggests unique transmission pathways for produce, which might reflect short shelf life or limited L. monocytogenes persistence (e.g., in agricultural environments). This study highlights new opportunities for use of whole-genome sequencing to improve outbreak investigations and source attribution.

Trichophyton fungal infections are common and increasingly complicated by terbinafine resistance. To support accurate molecular identification and resistance profiling, we provide a validated dataset of full-length squalene epoxidase (sqle) gene sequences from 493 Trichophyton isolates representing 18 species, addressing limited availability and misannotation of sqle sequences in public databases, particularly within the T. mentagrophytes complex. On the basis of that dataset, we designed 2 Sanger sequencing assays for simultaneously identifying species and detecting resistance-associated mutations. One targets the full-length gene, whereas the other amplifies a short region capturing all key resistance hotspots and species-specific single-nucleotide polymorphisms. The partial assay was evaluated on 66 clinical specimens and enabled clinically relevant species identification without internal transcribed spacer sequencing, supporting culture-independent detection. Of note, this approach differentiates T. indotineae from closely related species, overcoming a key diagnostic limitation and supporting clinical decision-making, surveillance, and management of resistant infections, despite limited resolution within certain species complexes.

Wickerhamomyces anomalus is a yeast rarely involved in human invasive fungal diseases (IFD). We retrospectively analyzed 44 episodes of W. anomalus IFD in France during 2012–2024. Injecting drug use (IDU) was the main risk factor among 26/35 (74.3%) incident cases. Most infections were community acquired; overall 3-month mortality rate was 1/30 (3.3%). Short tandem repeat (STR) genotyping and whole-genome sequencing analyses revealed substantial genetic diversity among isolates. However, 1 STR genotype was shared by 2 IDU patients, suggesting common exposure. In addition, 1 isolate obtained from a cotton filter used for drug preparation was identical by STR genotyping to the bloodstream isolate from the same patient, indicating direct inoculation via contaminated material or poor injection practices. Our findings highlight the increased risk for W. anomalus IFD among IDU patients and emphasize the importance of targeted preventive measures within that population.

Scrub typhus is a miteborne infectious disease caused by Orientia tsutsugamushi bacteria. In Japan, most cases occur in spring and autumn and are transmitted by Leptotrombidium pallidum and L. scutellare mites; summer scrub typhus, transmitted by L. akamushi mites, is rarely reported. In August 2024, a pregnant woman had scrub typhus develop after attending a fireworks event in Niigata Prefecture, Japan, resulting in fetal death. A Vietnam-related Karp-like O. tsutsugamushi genotype, distinct from the Kato type usually associated with L. akamushi mites, was detected from patient samples. Field investigations at the site of the fireworks event revealed seasonal predominance of L. akamushi mites in summer. We detected O. tsutsugamushi sequences identical to the patient’s strain in 3 L. akamushi mite larvae and 1 field mouse, suggesting that L. akamushi mites were the source of human infection. Our findings suggest reemergence of summer scrub typhus associated with infected L. akamushi mites carrying a locally novel genotype.

Rodentborne hantaviruses and lymphocytic choriomeningitis virus (LCMV) circulate in northern Italy but are rarely diagnosed. We tested samples collected from 371 patients during 2004–2018 and detected LCMV IgG in 2.7% of samples and hantavirus IgG in 7.3%. Puumala virus–neutralizing antibodies were confirmed in 10 cases, indicating unrecognized local hantavirus circulation.

We conducted a serologic study of domestic cats near the epicenter of the dairy cattle outbreaks of influenza A(H5N1) in California, USA. Three of the 12 cats sampled within 2 km of farms had neutralizing antibodies against H5N1 virus. Proximity to dairy farms was a statistically significant risk factor for seropositivity.

We describe a case of Acanthamoeba encephalitis with chronic lymphocytic leukemia (CLL) in the United States and summarize the Free-Living Ameba database to highlight CLL as the most common underlying malignancy for Acanthamoeba infections. CLL patients are more likely to have improved survival and nondisseminated cutaneous disease than those with other cancers.

Trichophyton indotineae is an emerging dermatophyte that is often resistant to terbinafine. We analyzed data produced by the Mass Spectrometry Identification global network. Those data revealed a 3-fold increase in T. indotineae identification during 2022–2025, demonstrating that this application is an effective tool for monitoring global spread of this pathogen.

A nationwide investigation identified 426 patients with Wickerhamomyces anomalus fungal cultures in South Africa; most cases clustered during May–November 2023. Case-patients lacked evidence of infection, indicating a pseudo-outbreak. Genomic and laboratory analyses implicated contaminated sterile lubricating gel. A nationwide product recall resulted in a decline in reported cases.

African swine fever virus genotype II was detected in wild boar in Spain in 2025 after >30 years of absence. Whole-genome sequencing and molecular follow-up of 8 representative cases identified a stable 9.8-kb deletion affecting the multigene family in the left variable region, defining an ASFV genotype II variant.

We report 2 cases of chronic subcutaneous infection in immunocompetent persons caused by Fomitiporella spp. basidiomycetes. Both patients recovered after surgical excision without antifungal therapy. We confirmed the cause of infection using broad-range fungal PCR from formalin-fixed tissue, highlighting the value of molecular diagnostics for detecting rare environmental fungi.

An ongoing measles outbreak in Israel, involving ≈3,200 cases and 16 deaths, threatens the country’s measles elimination status and reflects declining vaccination rates observed globally and within Israel. Epidemiologic investigations supported by sequencing suggest that a single importation triggered the outbreak, underscoring the critical role of rapid genomic surveillance in outbreak control.

A shipping container yard worker from Taiwan contracted laboratory-confirmed pulmonary coccidioidomycosis. He reported no travel history to endemic regions. Occupational exposure to aerosolized dust or soil residues on maritime shipping containers from endemic areas is likely. Our findings highlight international shipping as a potential pathway for introducing geographically restricted pathogens into nonendemic regions.

Southern tick–associated rash illness (STARI) is a tickborne disease of unknown etiology characterized by an erythema migrans–like skin lesion. We report a STARI case in New York in a child after an Amblyomma americanum tick bite; we detected Borrelia lonestari, a disputed cause of STARI, in the tick.

We evaluated pediatric tuberculosis treatment outcomes in a tertiary care center in France during 2014–2024 by using updated World Health Organization definitions. Among 123 children, 60.9% were successfully treated. Unfavorable outcomes reflected suboptimal adherence, dosing errors, and incomplete follow-up, highlighting the need for implementation and evaluation of optimized care processes.

Powassan virus is a tickborne flavivirus that can cause severe encephalitis in humans. After the first known human case in Illinois, USA, we detected Powassan virus in adult Ixodes scapularis ticks collected from 2 sites in northern Illinois during 2025. Phylogenetic analysis confirmed the virus as Powassan virus lineage II.

Brazilian spotted fever is a severe tickborne rickettsial disease endemic to Brazil. We report the clinical and epidemiological characteristics of an outbreak of 15 cases of Brazilian spotted fever caused by Rickettsia rickettsii in 2018 with high lethality. Our report highlights the need for early diagnosis to avert deaths.

Rickettsial disease caused by Rickettsia massiliae is rare in humans; only 6 cases have been reported since 2006. We report a case of R. massiliae infection in a pediatric patient in Spain with symptoms suggestive of rickettsiosis. Our results suggest that R. massiliae is an emerging tickborne rickettsial pathogen.

We report the establishment of the Gulf Coast tick (Amblyomma maculatum) and Rickettsia parkeri bacteria in Ohio, USA. We collected host-seeking ticks through surveillance in 2020–2021. Our discovery of established populations in 2 Ohio counties highlights a medically critical vector–pathogen system with serious public health implications.

We describe 5 cases of human Oropouche virus infection detected in rural Venezuela in 2025. All isolates belonged to the OROVBr_2015–2024 reassortant lineage linked to the 2024–2025 epidemic. Our results emphasize ongoing transmission, which highlights the need for strengthened surveillance and laboratory capacity in South America.

We report 7 recognized autochthonous cases of canine pythiosis, a fungal disease, identified in Italy during 2021–2024. All infected dogs had freshwater exposure. Cases involved multiple lakes and occurred over consecutive years. Sequenced isolates clustered within clade IV of the Pythium insidiosum complex, currently designated Pythium periculosum.

Western equine encephalitis virus (WEEV) reemerged in Argentina during 2023–2024, raising public health concerns and posing a potential threat to blood transfusion safety. We assessed the effect of WEEV circulation on the blood supply by implementing responsive, community-informed interventions within a regional hemovigilance system, including epidemiologic mapping, enhanced donor selection criteria, and alphavirus-specific nucleic acid testing. Among 637 donors residing in outbreak-affected areas, we detected 1 asymptomatic viremic donor. Phylogenetic analysis showed that the viral sequence clustered within the contemporary South American outbreak lineage, consistent with ongoing regional transmission. Those findings demonstrate silent WEEV circulation among blood donors and highlight the critical role of donor surveillance as a sentinel system for emerging arboviruses. Hemovigilance provides valuable insights into viral circulation in the broader population, underscoring the need to integrate molecular surveillance into routine blood bank practices to strengthen transfusion safety and public health preparedness.

Trichinella spp. nematodes are parasites that can cause trichinellosis in humans after consumption of infected, undercooked meat. A November 2024 trichinellosis outbreak in western North Carolina, USA, resulted in 3 cases (2 probable, 1 confirmed), all linked to undercooked bear jerky. In total, 6 persons consumed the implicated meat (attack rate 50%). Molecular testing identified Trichinella spiralis in leftover meat from the same bear. This outbreak provides evidence of changing trichinellosis patterns. Low-cost safety measures and prevention efforts regarding safe wild game preparation are needed to avoid future outbreaks.

Anaplasmosis, an emerging tickborne zoonosis, infrequently involves the central nervous system, and cerebrospinal fluid (CSF) profiles of anaplasmosis remain poorly characterized. We conducted a multisite retrospective study of patients hospitalized with anaplasmosis during November 1, 2014–November 29, 2024, in Minnesota and Wisconsin, USA, a hyperendemic region. Included patients had anaplasmosis confirmed by PCR on blood samples, exhibited neurologic symptoms, and had lumbar puncture procedures. Ten hospitalized patients met inclusion criteria, 6 with meningitis, 3 with meningoencephalitis, and 1 with encephalitis. CSF findings were within reference ranges for 5 patients; 4 patients demonstrated mild lymphocytic pleocytosis, but glucose and protein levels were within reference ranges. One patient underwent a traumatic lumbar puncture resulting in neutrophilic pleocytosis. CSF abnormalities did not correlate with neurologic severity, suggesting a cytokine-mediated process rather than direct central nervous system infection. All patients rapidly improved with doxycycline, highlighting the need for early recognition and empiric therapy for anaplasmosis.

Diagnosis of coccidioidomycosis is challenging and requires a high index of clinical suspicion. We estimated the incidence and duration of, and risk factors associated with, diagnostic delays and missed opportunities in the diagnosis of coccidioidomycosis. We conducted a retrospective analysis of health insurance claims data in the United States during 2001–2022 included in the Merative MarketScan Databases. Using a case-crossover design and a bootstrapping approach, we estimated the number of excess visits for coccidioidomycosis-related symptoms before diagnosis. We also evaluated potential factors associated with delay. We estimated that almost 60% of patients experienced >1 missed opportunity for diagnosis; the average diagnostic delay was 29.69 (95% CI 28.25–31.18) days. Missed opportunities were predominantly observed in outpatient settings (73%) and were significantly associated with older age, rural residence, underlying pulmonary conditions, and prescriptions for antibiotics or inhalers. Diagnostic delays for coccidioidomycosis are common, and addressing such delays could improve clinical outcomes.

Snowshoe hare virus (SSHV) is an arbovirus in the California serogroup known to circulate throughout Canada and northern latitudes of the United States. The clinical spectrum of SSHV infection ranges from asymptomatic or mild febrile illness to neuroinvasive disease; neuroinvasive disease occurs more often in children and young adults. We describe a cluster of confirmed and probable SSHV meningoencephalitis cases in 3 children from Whistler, British Columbia, Canada, in the summer of 2024. We highlight the shared epidemiology, clinical manifestations, serologic diagnostic methods, and outcomes for the cases. All 3 children acquired the infection locally and made a full recovery. This case series suggests underrecognized SSHV infection prevalence that warrants enhanced surveillance and review of existing diagnostic algorithms. California serogroup viruses, including SSHV, should be recognized as a potential cause of neuroinvasive disease in North America during mosquito season, particularly when initial diagnostic testing is inconclusive.

Blastomyces urine antigen testing is a sensitive blastomycosis diagnostic method, but its utility for active case identification during outbreaks is unknown. We evaluated urine antigen testing for identifying blastomycosis cases during a 2023 outbreak at a Michigan, USA, paper mill and assessed demographic and clinical factors associated with test positivity. Approximately 2 months after the outbreak was recognized, we collected work and health information for 603 employees; 95% (n = 578) underwent urine antigen testing and 9% (n = 52) tested positive, including 25 previously undetected cases. Blastomycosis-like symptoms were associated with test positivity (p<0.001), but 10% of employees with positive results were asymptomatic. Recent hospitalization for blastomycosis was associated with test positivity (p = 0.02) and higher antigen levels. Further research into urine antigen testing is needed clarify its suitability for detecting mild and asymptomatic infections during outbreak investigations. Urine antigen testing had high acceptability among employees and effectively identified additional cases.

Reports of ocular manifestations of Lyme disease (LD) are uncommon, and signs and symptoms may be overlooked by physicians. We conducted a retrospective case series of ocular LD reported during 1988–2025. Among 27 published reports in PubMed, we noted that, in 38 cases, the most common ocular manifestation was uveitis, representing 45% of cases, followed by optic neuritis and cranial nerve palsies (including trochlear and abducens). Not all cases met Centers for Disease Control and Prevention surveillance guidelines for LD, given that some case reports were published before the current guidelines. Cases that provided microbiologic proof were 2 anterior uveitis cases, 1 case of anterior uveitis with abducens’s nerve palsy, 1 case of intermediate uveitis, and 1 case of intranuclear ophthalmoplegia. Ocular LD can have a broad variety of manifestations; therefore, physicians should be aware of those manifestations and obtain microbiologic proof for a more definitive diagnosis and epidemiologic value when possible.

Group A Streptococcus (GAS) causes a variety of diseases in humans but is not widely appreciated as a cause of meningitis. During 1997–2022, ten sites participating in the Active Bacterial Core Surveillance network in the United States identified GAS meningitis cases. We calculated annual incidence and case-fatality rates (CFRs) for 320 of those cases and determined antimicrobial resistance by whole-genome sequencing. Annual incidence of GAS meningitis ranged from 0.02 to 0.07 cases/100,000 persons. Children <1 year of age had the highest average annual incidence, 0.23 cases/100,000 children. GAS meningitis had a higher CFR (19.4%) than meningitis caused by group B Streptococcus, Streptococcus pneumoniae, Neisseria meningitidis, or Haemophilus influenzae. Clindamycin resistance among GAS meningitis isolates increased from 3.2% during 1997–2002 to 17.7% during 2018–2022. Clinicians should be aware that meningitis is an uncommon but severe manifestation of invasive GAS and has a higher CFR than more established meningitis etiologies.

A previous study demonstrated noninferior efficacy of 4-month rifapentine/moxifloxacin regimen for tuberculosis (TB) treatment compared with the standard regimen. We analyzed pregnancy outcomes of women who became pregnant during the study. Among 740 women, 97 (13.1%) became pregnant. Of 102 pregnancies (in 97 participants), 30 (29.4%) participants were exposed to study drugs. Fetal loss was reported for 3/13 (23.1%) in the control regimen, 1/9 (11.1%) in the rifapentine/moxifloxacin regimen, and 1/8 (12.5%) in the rifapentine regimen. Among 21 live births in exposed pregnancies (7 in each arm), 1 infant with a congenital anomaly was reported in a participant on the rifapentine regimen. Among women receiving a short rifapentine/moxifloxacin regimen for tuberculosis who became pregnant, we observed no elevated rates of fetal losses or congenital anomalies.

Haematospirillum jordaniae was first identified as a human pathogen in 2016. In this article, we describe 4 patients who had H. jordaniae infections identified in 2020 and who had temporally and spatially linked environmental exposures. Three of the 4 patients reported leg injuries while participating in recreational river water activities in south-central Pennsylvania, USA. In 2024, we detected H. jordaniae in river samples collected at locations identified during patient interviews. All patients sought emergency department services for clinical assessment; however, the causative bacterial isolate was not initially identified. H. jordaniae was identified as the bacterial cause months after patient treatment and discharge. Although H. jordaniae infections are considered rare, the true occurrence is unknown. Additional information about the organism’s ecology and environmental seasonality could guide public health messaging and increase awareness among healthcare providers.

Reptile-associated outbreaks of human Salmonella infections are increasing in Canada, coinciding with a rise in the popularity of reptiles as pets. We conducted a retrospective analysis of surveillance data for human Salmonella case-patients in Ontario during 2015–2022. We compared serotypes and reptile types for those reporting domestic reptile or amphibian exposure with veterinary Salmonella isolates reported during the same period. Case-patients commonly reported contact with reptile types from which Salmonella was most frequently isolated. Some serotypes from human case-patients were closely associated with contact with specific reptile types, including Salmonella Paratyphi B biovar Java (Salmonella Paratyphi B variant L (+) tartrate +) with snakes, Salmonella Agbeni with turtles, and Salmonella Cotham, Salmonella Chester, and Salmonella Tennessee with bearded dragons. Salmonella was most likely to be reported from reptiles fed a carnivorous diet. Education of reptile owners could help promote proper veterinary care and reduce transmission of zoonotic infections.

Candida bloodstream infections, and their increasing antifungal resistance, are a global concern. In this cross-sectional study, we analyzed 2,443 culture-confirmed candidemia cases reported in South Africa during 2012–2017 to assess the effect of previous antifungal exposure on nonsusceptible Candida infection. We classified cases by species resistance profile and patient’s antifungal use within 14 days before infection. We found that 48% of cases were caused by nonsusceptible species, and 20% of patients had prior antifungal exposure, mainly to fluconazole. In patients >90 days of age, prior antifungal use was significantly associated with nonsusceptible Candida bloodstream infection (adjusted OR 2.02, 95% CI 1.43–2.87; p<0.001), with species-specific effects. No such association was found in neonates and young infants, for whom hospital transmission appeared more influential. Our findings underscore the need for targeted antifungal stewardship and enhanced infection prevention to mitigate antifungal resistance in South Africa.