Articles from Emerging Infectious Diseases

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.

During 2022–2024, six cases of invasive fungal infection occurred among immunocompromised patients at Marseille University Hospital, Marseille, France. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry initially identified Trichosporon inkin fungi. However, phylogenetic analysis of intergenic spacer region 1 and whole-genome sequences revealed the genetically distinct species T. austroamericanum. Analysis of core genome and mitogenome from 6 patient isolates and 1 environmental isolate revealed substantial genetic diversity among T. austroamericanum strains, indicating a polyclonal outbreak. Furthermore, the mitochondrial genome emerged as a potential marker for intraspecies differentiation, which potentially could aid in epidemiologic investigations. Identified in 2024 but potentially underestimated, T. austroamericanum has since been reported in case clusters from hospital settings in France, highlighting the need for accurate fungal identification and suggesting previously identified T. inkin cases should be re-evaluated for T. austroamericanum. Clinical T. austroamericanum is emerging in hospital settings and should be included in the differential diagnosis of fungal infections.

The tickborne bacterial pathogen Neoehrlichia mikurensis has been detected in <1% of blood donors in Sweden. N. mikurensis can give rise to asymptomatic persistent infections. Up to 25% of Ixodes ricinus ticks in southern Norway are infected with N. mikurensis. We investigated the incidence of N. mikurensis infection among blood donors in this region. We detected N. mikurensis in the blood of 45/499 (9%) blood donors by independent PCR methods; 69% of those were repeatedly positive 1–7 months after the first detection and tested negative after doxycycline treatment. We tested 8/19 adult recipients of potentially infected blood; none tested positive for N. mikurensis at the time of testing (191–301 days after transfusion). Our study identified a very high rate of infection with N. mikurensis in blood donors in Norway; whether infection can be transmitted by transfusion of blood products, however, remains unclear.

Among >25,000 invasive pneumococcal disease isolates recovered in US locations during 2015–early 2024 through population-based surveillance, we detected 17 case isolates carrying the lsaC gene, which has been shown to confer resistance to clindamycin in group B Streptococcus. Sixteen isolates carried the mef, msrD, tetM, and lsaC genes on a 29-kb mobile element acquired through an interspecies recombination event and were intermediately clindamycin resistant. One isolate acquired a 62-kb mobile element containing the ermB, tetM, and lsaC genes through a transposition event. All 17 cases were in adults, including 4 adults experiencing homelessness and 9 with substance abuse problems. All 17 lsaC-positive isolates shared a 5.2-kb lsaC-containing element precisely integrated within the conserved oriT site of their respective mobile element. Those 17 lsaC-positive strains were all serotype 20, multilocus sequence type 1257, and were recovered recently (2021–2024); isolates 1–16 represented emergent disease clusters in New York and Connecticut.

Respiratory virus indicators were unreliable at the onset of the COVID-19 pandemic when testing availability was limited and residents with mild symptoms were advised to avoid unnecessary medical care. The Los Angeles County Department of Public Health (Los Angeles, California, USA) developed Angelenos in Action (AiA), a text message–based community syndromic surveillance system to monitor respiratory illness trends. Approximately 17,000 unique participants responded >1 time; 43% of participants continue to regularly respond to the survey. We assessed AiA’s performance by measuring correlation coefficients with reported COVID-19 case counts (0.975), sentinel laboratory SARS-CoV-2 test positivity rate (0.762), and wastewater SARS-CoV-2 concentrations (0.861). AiA performed strongly against 3 comparator surveillance methods and correlated particularly well with raw case counts. A moderate correlation was also noted between influenza test positivity rate and AiA data, indicating the system has potential to detect respiratory illness besides COVID-19.

In 2020, a novel spotted fever group Rickettsia was described in 3 clinically ill dogs in the United States. Using naturally infected canine blood, the novel Rickettsia sp. was isolated in epithelial (Vero E6) and mononuclear (DH82 and 030D) cell lines. The sequenced whole genome revealed a 1.27 Mb circular chromosome with 96.87% identity to Rickettsia raoultii on the basis of average nucleotide identity analysis. A maximum-likelihood phylogeny tree placed the novel Rickettsia in its own branch within the spotted fever group. Immunofluorescence revealed single rods localized along the membrane in epithelial cells and randomly distributed in the cytoplasm of mononuclear cells. We propose the name Rickettsia finnyi sp. nov., strain 2024-CO-Wats, which is available from national and international Rickettsial isolate reference collections. Fever and thrombocytopenia were among abnormalities in the 17 naturally infected dogs we describe, underscoring the pathogenic importance of R. finnyi sp. nov. and its potential public health relevance.

Mpox is a reemerging infectious disease caused by monkeypox virus (MPXV). Whole-genome sequencing provides comprehensive surveillance of MPXV but is challenging in resource-limited outbreak settings and on clinical samples with low viral load. We developed a low-cost, high-throughput partial-genome sequencing strategy and a freeware Nextflow pipeline for MPXV genomic surveillance. We targeted 2 genomic regions of MPXV by using short overlapping amplicons. This amplicon-based approach generated high-quality sequences over the 2 genomic regions from clinical specimens, including samples with low viral DNA and from formalin-fixed tissues. This partial-genome sequencing approach can determine MPXV subclades and offers an attractive strategy to lower cost and improve MPXV surveillance during outbreaks in mpox-endemic and -nonendemic countries.

We report 3 cases of probable invasive pulmonary disease caused by Bjerkandera spp. fungi in immunocompromised patients in Germany. Accurate identification required internal transcribed spacer sequencing. Response to antifungal treatment varied. Our report underlines the pathogenic potential of Bjerkandera spp. and the importance of molecular diagnostics in rare fungal infections.

We sequenced a novel rhabdovirus, Tupavirus delphini (dolphin tupavirus), from the brain of a stranded dead Atlantic white-sided dolphin with severe encephalitis in Canada. In situ hybridization linked presence of the virus to the animal’s brain pathology and death. Our findings underscore the importance of monitoring marine mammals for unexpected pathogens.

By using PCR testing, we found Neoehrlichia mikurensis DNA in 1.1% of ticks removed from persons in Sweden and Finland. Symptoms developed in 2 immunocompetent persons. Despite low transmission risk, infection can occur after short tick attachment. Our findings highlight the need to consider N. mikurensis in patients with unexplained symptoms after tick bite.

Dengue remains a major public health challenge. In Costa Rica, we implemented nationwide genomic surveillance to track dengue virus serotype 2 cosmopolitan genotype emergence. Phylogenetic and eco-epidemiologic analyses revealed early detection, climate-driven spread, and spatial heterogeneity. Our findings underscore the need for integrated surveillance to guide adaptive responses to emerging arboviral threats.

The prevalence of Spiroplasma ixodetis in ticks that have bitten humans in Sweden and in the Åland Islands, Finland, was 2.6%, with observed significant geographic differences between regions. The pathogen was not detected in blood samples from participants bitten by S. ixodetis–positive ticks, indicating low risk for transmission to humans.

We describe 2 cases of autochthonous human anaplasmosis in Washington, USA, where anaplasmosis has been rarely reported. Clinicians should consider anaplasmosis in the differential diagnosis for patients with compatible clinical symptoms after tick bite or time spent outdoors in an area where Ixodes pacificus ticks are present.

We report Borrelia afzelii hepatitis in an immunosuppressed patient in Switzerland receiving anti-CD20 therapy and venetoclax. Diagnosis was made by metagenomic sequencing and PCR. This case underscores the need to consider Lyme borreliosis in unexplained hepatitis cases and highlights the value of molecular diagnostics in immunosuppressed patients when serologic test results are negative.

We report 2 cases of febrile lymphocytic meningitis with encephalitis in patients in France. One patient had not traveled outside Paris; the other had traveled to eastern France. Laboratory findings revealed acute West Nile virus infection. The cases occurred days apart, raising concern the virus has spread further in France.

We describe the clinical symptoms and epidemiologic characteristics of a patient infected with avian influenza A(H10N3) virus in Guangxi Province, China, in December 2024. Whole-genome sequencing showed that the virus was highly homologous to a virus from Yunnan Province. H10 subtype viruses should be monitored for potential zoonotic or reassortant events.

We report detection of Aedes (Fredwardsius) vittatus mosquitoes in continental North America, in Yucatán, Mexico. Phylogenetic analysis clustered the sequence from mosquitoes collected in Mexico with Caribbean mosquito lineages, suggesting species introduction via the Caribbean. Given its arbovirus competence, urgent inclusion of the Ae. vittatus mosquito in surveillance programs is warranted.

We report an unvaccinated traveler from the United States who contracted fulminant fatal tick-borne encephalitis while visiting Switzerland. Climate changes and international travel are intensifying tick exposure for unvaccinated persons. The increasing incidence of tick-borne encephalitis across Europe underscores the importance of tick bite prevention and vaccination against tick-borne encephalitis virus.

We conducted a nationwide serologic and molecular survey to elucidate the epidemiologic status of Crimean-Congo hemorrhagic fever virus in Israel. We found serologic and molecular evidence of virus circulation in the country. Future human cases could be prevented by increasing public awareness and implementing public health measures.

A patient with extensively drug-resistant tuberculosis in Lesotho recovered successfully after failed treatment with bedaquiline, delamanid, linezolid, and clofazimine. Whole-genome sequencing and broth microdilution testing results were not in agreement, illustrating the urgent need for studies that correlate phenotypic and genotypic resistance testing with clinical response.

To investigate local transmission of Orientia tsutsugamushi by chiggers in North Carolina, USA, we tested remnant serum specimens from patients with eschar undergoing testing for suspected tickborne disease. We identified 11 persons with O. tsutsugamushi antibodies, including 4 who were positive by both assays; none had severe clinical manifestations consistent with scrub typhus.

We report mortality in rainbow snakes in Virginia and North Carolina, USA, linked to snake fungal disease caused by Ophidiomyces ophidiicola. During 2013–2023, we observed 46 dead rainbow snakes with lesions indicative of snake fungal disease, noted elevated disease severity compared with other species, and recorded fewer live snakes over time.

We detected dengue virus serotype 3 in 11.8% (16/136) of febrile patients in Luanda Province, Angola, during April and July 2024. Our genetic analyses reveal that dengue virus serotype 3 lineage III_B.3.2 probably was imported from the Americas into Angola in late 2022 and then spread through local transmission.

We detected yellow fever virus by using quantitative PCR in Aedes albopictus mosquitoes and isolated the virus in C6/36 cells in 4 of 18 pools, including 118 specimens collected in an urban green area in São Paulo State, Brazil. Additional monitoring to detect shifts in transmission of this species is warranted.

We report 4 dengue cases in travelers returning to Israel from Sharm-El-Sheikh, Egypt, all confirmed as dengue virus type 2 infections. Phylogenetic analysis showed clustering with strains from Pakistan. Our findings provide molecular evidence of dengue circulation in the Sinai desert, highlighting the need for increased awareness among travelers and health authorities.

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.

The complexity of rickettsial serodiagnostics during acute illness has limited clinical characterization in Africa. We used archived samples from sepsis (n = 259) and acute febrile illness (n = 70) cohorts in Uganda to identify spotted fever and typhus group rickettsiae by using immunofluorescence assay and clinically validated rRNA reverse transcription PCR (RT-PCR). Among 329 participants, 10.0% had rickettsial infections (n = 33; n = 20 identified with immunofluorescence assay and n = 13 by RT-PCR). Serum rRNA RT-PCR was 75.0% (95% CI 42.8–94.5%) sensitive and 91.2% (95% CI 85.8–95.1%) specific. Thrombocytopenia was more common among patients with rickettsial infections than with other nonmalarial infections (adjusted odds ratio 3.7; p = 0.003). No participants were on a tetracycline antimicrobial drug at admission. rRNA RT-PCR is a promising diagnostic strategy for identifying acute rickettsial infections. Doxycycline should be included in empiric antimicrobial drug regimens for nonmalarial febrile illness in this region.

Prevalence of emerging fungal infections is increasing, particularly among immunocompromised persons, children, and older persons. We report 108 cases of Scheffersomyces spartinae infection in pediatric patients from Karachi and other cities in Pakistan, of which 107 were identified from blood cultures. Cultures were initially misidentified as Clavispora lusitaniae by a biochemical assay before speciation as S. spartinae by whole-genome sequencing. All isolates were from children <12 years of age, and >69% were from children <1 month of age. Isolates were genetically distinct across regions of Pakistan; however, genetic diversity was low in isolates from patients in Karachi and nearby Nawabshah and had median differences of just 9 pairwise nucleotide variants. This study demonstrates S. spartinae is a potentially emerging pathogen in neonates and young infants in Pakistan. The findings highlight the limitations of phenotypic identification for detecting emerging fungal infections and underscore the value of molecular identification approaches.

Mpox was first identified against the backdrop of the smallpox eradication campaign. Monkeypox virus (MPXV), the causative agent of mpox, has been maintained in animal reservoirs in the forested regions of West and Central Africa as 2 distinct clades; clade I has historically caused more severe infection in Central Africa than clade II, historically found in West Africa. However, rapid reemergence and spread of both MPXV clades through novel routes of transmission have challenged the known characteristics of mpox. We summarize mpox demographic distribution, clinical severity, and case-fatality rates attributed to genetically distinct MPXV subclades and focus on MPXV clade Ib, the more recently identified subclade. Broad worldwide assistance will be necessary to halt the spread of both MPXV clades within mpox endemic and nonendemic regions to prevent future outbreaks.

Talaromycosis is a life-threatening fungal disease that primarily affects immunocompromised persons in Southeast Asia. We conducted a multicenter, case–control study recruiting participants with advanced HIV disease in Vietnam; 205 case-patients with culture-confirmed talaromycosis were matched to 405 control-patients by age, sex, and CD4 count. Occupational exposure to tropical plants (odds ratio [OR] 1.73 [95% CI 1.10–2.73]; p = 0.017) and to farmed animals (OR 2.07 [95% CI 1.20–3.55]; p = 0.009) were independent risk factors for talaromycosis. Talaromycosis risk was higher in participants from highland regions than in persons from lowland regions (p<0.05). Participants from lowland regions who had lived or traveled to highland regions had a higher risk for talaromycosis (OR 3.15 [95% CI 1.49–6.64]; p = 0.003). This study confirms the epidemiologic correlation between talaromycosis and soil exposure and demonstrates an epidemiologic link between talaromycosis and residence in or travel to highland regions of Vietnam.

Spiroplasma ixodetis has been reported to cause the rare combination of cataract and uveitis in infants. Through a retrospective analysis of available literature and additional unpublished cases, we identified 28 eyes from 18 infants from 8 countries in Europe with cataracts and intraocular inflammation. The cataracts were bilateral in 55.6%, unilateral in 44.4%, and progressive in 46.4% of patients. Granulomatous anterior uveitis was found in all infants. Presence of S. ixodetis was supported by PCR (positive in 89.3% of eyes tested), transmission electron microscopy (positive in 90% of eyes tested), or culture of aspirated lens material (positive in 87.5% of eyes tested). Treatment with macrolide antimicrobial drugs, corticosteroids, and lensectomy appeared to be effective. Two patients had a recurrence of the uveitis after lens extraction and needed prolonged treatment. To increase awareness of S. ixodetis, we suggest its inclusion with the organisms of the TORCH acronym.

During 2007–2020, we conducted a cross-sectional prevalence study among patients with acute undifferentiated febrile illness to describe the burden and long-term epidemiology of rickettsioses in Cambodia. Serum samples were collected from 10,243 participants, along with epidemiologic data, information on clinical symptoms, demographic characteristics, and risk factors. A total of 802 (7.8%) participants met the definition for acute rickettsial infection after ruling out malaria, influenza, dengue, and chikungunya; 557 (5.4%) cases were typhus, 154 (1.5%) spotted fever, and 136 (1.3%) scrub typhus. Overall seroprevalence was 18.1% (1,857/10,243). Increased age, residence in urban settings, and recent travel to forests were significantly associated with rickettsial infection. Symptoms significantly associated with infection included rash, vomiting, and skin lesions. Our results confirm the underlying burden of rickettsioses and associated risk factors in Cambodia and highlight the need for accessible diagnostics and clinical guidance that consider rickettsioses when treating persons with acute undifferentiated febrile illness.

Invasive aspergillosis (IA) caused by Aspergillus flavus remains poorly described. We retrospectively analyzed 54 cases of IA caused by A. flavus reported in France during 2012–2018. Among cases, underlying IA risk factors were malignancy, solid organ transplantation, and diabetes. Most (87%, 47/54) infections were localized, of which 33 were pleuropulmonary and 13 were ear-nose-throat (ENT) infection sites. Malignancy (70% [23/33]) and solid organ transplantation (21% [7/33]) were the main risk factors in localized pulmonary infections, and diabetes mellitus was associated with localized ENT involvement (61.5%, [8/13]). Fungal co-infections were frequent in pulmonary (36%, 12/33) but not ENT IA (0 cases). Antifungal monotherapy was prescribed in 45/50 (90%) cases, mainly voriconazole (67%, 30/45). All-cause 30-day case-fatality rates were 39.2% and 90-day rates were 47.1%, and rates varied according to risk factor, IA site, and fungal co-infections. Clinicians should remain vigilant for A. flavus and consider it in the differential diagnosis for IA.

Risk factors for developing bloodstream infections (BSIs) caused by Aerococcus bacteria remain insufficiently examined. In this nationwide case–control study in Sweden, 19 of 23 clinical microbiological laboratories identified patients who had aerococcal BSIs during 2012–2016. We compared each of those index patients with 4 controls matched for age, sex, and county of residence. Overall, 588 episodes of aerococcal BSI occurred over 39.6 million person-years, corresponding to an average incidence of 1.48/100,000 person-years (95% CI 1.37–1.60/100,000 person-years). Most infections developed in men >65 years of age. Aerococcal BSI was associated with neurologic (adjusted odds ratio 2.89 [95% CI 2.26–3.70]) and urologic (adjusted odds ratio 2.15 [95% CI 1.72—2.68]) conditions and previous hospitalization or infection treatment. Our findings support the previously observed predilection for aerococcal BSIs developing in elderly men with urinary tract disorders. Awareness of Aerococcus spp. in patients, especially elderly men, will be needed to manage invasive infections.

Tularemia, a zoonosis caused by Francisella tularensis, is endemic in Baden-Wuerttemberg, Germany. To determine tularemia epidemiology in this region, we characterized the genetic diversity of F. tularensis in human and animal isolates during 2012–2022 by using whole-genome sequencing, combined with human and veterinary surveillance data analysis. Human case numbers varied; most cases occurred in 2021 (n = 34). Arthropod bites were reported most in cases with information on animal exposure (45%, n = 43). Poisson regression confirmed a significant increase in human cases during the study period (p<0.001). No seasonal pattern was identified, but case numbers were lowest in winter. Human surveillance data often lacked exposure details. Positivity rates in animals were 5%–34%, increasing since 2017. Human isolates often clustered with hare-derived strains, although transmission routes often remain unclear. These findings emphasize the importance of combining genome sequencing with detailed epidemiologic tracing to identify infection sources and improve surveillance data.

A previous study demonstrated noninferior efficacy of 4-month rifapentine/moxifloxacin regimen for tuberculosis (TB) treatment compared with the standard regimen. We explored results among study participants with diabetes. Among 2,516 randomized participants, 181 (7.2%) had diabetes. Of 166 participants with diabetes in the microbiologically eligible analysis group, 26.3% (15/57) had unfavorable outcomes in the control regimen, 13.8% (8/58) in the rifapentine/moxifloxacin regimen, and 29.4% (15/51) in the rifapentine regimen. The difference in proportion of unfavorable outcomes between the control and rifapentine/moxifloxacin arms in the microbiologically eligible analysis group was –12.5% (95% CI –27.0% to 1.9%); the difference between the control and rifapentine arms was 3.1% (95% CI –13.8% to 20.0%). Safety outcomes were similar in the rifapentine/moxifloxacin regimen and control arms. Among participants with TB and diabetes, the rifapentine/moxifloxacin arm had fewest unfavorable outcomes and was safe. Our findings indicate that the rifapentine/moxifloxacin regimen can be used in persons with TB and diabetes.

Human ehrlichiosis is a potentially fatal tickborne disease caused by 3 species: Ehrlichia chaffeensis, E. ewingii, and E. muris eauclairensis. In the United States, 234 confirmed cases of E. ewingii ehrlichiosis were reported to the Centers for Disease Control and Prevention through the National Notifiable Diseases Surveillance System during 2013–2021; average annual incidence was 0.08 cases/1 million population. E. ewingii ehrlichiosis was reported more commonly among older, White, non-Hispanic, and male patients. Incidence and case counts generally increased yearly, except for 2020 and 2021. The highest number of cases were reported from Missouri and Arkansas. We report the geographic expansion of E. ewingii ehrlichiosis and the continued public health challenge of clarifying clinical manifestations of this infection. Clinician education will be essential to implement molecular assays to properly diagnose E. ewingii infection in patients and gain a better understanding of the epidemiology of this emerging disease.

A global increase in the incidence of invasive group A Streptococcus (iGAS) infections was observed after lifting of COVID-19 related restrictions in 2022, and type M1_UK dominated in many countries. After seasonal declines in iGAS incidence during the summer of 2023, simultaneous, rapid expansion of a previously rare emm type 3.93 was seen beginning in November, increasing to 20% of all cases in England and 60% of all cases in the Netherlands within 4 months. emm3.93 was associated with iGAS in children 6–17 years of age and with increased risk for pneumonia or pleural empyema and meningitis in both countries. No excess risk of death was identified for emm3.93 compared with other types. Genomic analysis of historic and contemporary emm3.93 isolates revealed the emergence of 3 new clades with a potentially advantageous genomic configuration. Our findings demonstrate the value of molecular surveillance, including long-read sequencing, in identifying clinical and public health threats.

Rickettsia sibirica mongolitimonae is an emerging cause of tickborne rickettsiosis. Since the bacterium was first documented as a human pathogen in 1996, a total of 69 patients with this infection have been reported in the literature. Because of the rising rate of R. sibirica mongolitimonae infection cases, we evaluated the epidemiologic and clinical features of 29 patients who had R. sibirica mongolitimonae infections confirmed during 2007–2024 at the Center for Rickettsiosis and Arthropod-Borne Diseases, the reference laboratory of San Pedro University Hospital–Center for Biomedical Research of La Rioja, Logroño, Spain. We also reviewed all cases published in the literature during 1996–2024, evaluating features of 94 cases of R. sibirica mongolitimonae infection (89 in Europe, 4 in Africa, and 1 in Asia). Clinicians should consider R. sibirica mongolitimonae as a potential causative agent of rickettsiosis, and doxycycline should be administered promptly to avoid clinical complications.