During 2023-2024, highly pathogenic avian influenza A(H5N1) viruses from clade 2.3.2.1c caused human infections in Cambodia and from clade 2.3.4.4b caused human infections in the Americas. We assessed the susceptibility of those viruses to approved and investigational antiviral drugs. Except for 2 viruses isolated from Cambodia, all viruses were susceptible to M2 ion channel-blockers in cell culture-based assays. In the neuraminidase inhibition assay, all viruses displayed susceptibility to neuraminidase inhibitor antiviral drugs oseltamivir, zanamivir, peramivir, laninamivir, and AV5080. Oseltamivir was ≈4-fold less potent at inhibiting the neuraminidase activity of clade 2.3.4.4b than clade 2.3.2.1c viruses. All viruses were susceptible to polymerase inhibitors baloxavir and tivoxavir and to polymerase basic 2 inhibitor pimodivir with 50% effective concentrations in low nanomolar ranges. Because drug-resistant viruses can emerge spontaneously or by reassortment, close monitoring of antiviral susceptibility of H5N1 viruses collected from animals and humans by using sequence-based analysis supplemented with phenotypic testing is essential.

We used clinical metagenomic next-generation sequencing of cerebrospinal fluid to investigate bunyavirus infections in 2 immunocompromised patients in the United States who had fatal meningoencephalitis. Potosi virus has been isolated from mosquito vectors and Lone Star virus from tick vectors. These findings highlight the power of metagenomic next-generation sequencing in broad-based, agnostic detection of emerging viral infections that test negative using conventional targeted diagnostic methods.

Since March 2024, highly pathogenic avian influenza A(H5N1) viruses have caused outbreaks in dairy cattle and poultry in the United States, and they continue to spill over into humans. However, data on human immune response to those viruses is limited. We report neutralizing antibody responses in 2 dairy farm worker H5N1 cases.

Outbreak investigation is an essential component of tuberculosis (TB) control in the United States, but its epidemiologic impact and cost-effectiveness have not been quantified. We modeled outbreak investigation activities in the United States during 2023-2032 and estimated corresponding epidemiologic impact, economic costs (in 2022 US$), and incremental cost-effectiveness ratios from the healthcare system perspective (cost per additional quality-adjusted life-year gained). We projected that outbreak investigations would result in 1,030,000 (95% uncertainty interval [UI] 376,000-1,740,000) contacts investigated, leading to 4,130 (95% UI 1,420-7,640) TB diagnoses and 104,000 (95% UI 37,600-181,000) latent TB infection diagnoses, at a total cost of US $219 million (95% UI $80-$387 million). We estimated that 5,560 (95% UI 1,720-11,400) TB cases would be averted through early detection and treatment, and the incremental cost-effectiveness of outbreak investigations, compared with no outbreak investigations, was $27,800 per quality-adjusted life-year gained (95% UI $4,580-$68,700).

Tickborne infections are challenging to diagnose, particularly among solid organ transplant recipients. We report a US case of donor-derived ehrlichiosis from a living kidney donation that highlights how screening for living donors may miss tickborne infections. Clinicians should consider the epidemiology of the donor when screening donations and evaluating recipients for donor-derived infection.

Reports of human infections with influenza A(H5N1) clade 2.3.4.4b viruses associated with outbreaks in dairy cows in the United States underscore the need to assess the potential cross-protection conferred by existing influenza immunity. We serologically evaluated ferrets previously infected with an influenza A(H1N1)pdm09 virus for cross-reactive antibodies and then challenged 3 months later with either highly pathogenic H5N1 clade 2.3.4.4b or low pathogenicity H7N9 virus. Our results showed that prior influenza A(H1N1)pdm09 virus infection more effectively reduced the replication and transmission of the H5N1 virus than did the H7N9 virus, a finding supported by the presence of group 1 hemagglutinin stalk and N1 neuraminidase antibodies in preimmune ferrets. Our findings suggest that prior influenza A(H1N1)pdm09 virus infection may confer some level of protection against influenza A(H5N1) clade 2.3.4.4.b virus.

Seasonal cyclosporiasis outbreaks occur in the United States every year. To better understand the disease, the Centers for Disease Control and Prevention developed a novel genotyping system that successfully clusters nonclonal eukaryotes. We examined temporal-geographic distributions of Cyclospora cluster consensus genotypes (CCGs) and applied regression analyses to identify correlations between Cyclospora spp. parasites and clinical manifestations or epidemiologic risk factors, using data collected during 2018-2021. No CCG was uniquely associated with or consistently detected in a state during the study, suggesting that cyclosporiasis in the United States is likely caused by frequent parasite introductions. We identified positive associations between infection with C. ashfordi and C. cayetanensis and consumption of specific produce items: cilantro, mango, and onion for C. ashfordi and iceberg lettuce, carrot, and cauliflower for C. cayetanensis. Our findings can guide future research into public health interventions aimed at reducing the burden of cyclosporiasis in the United States.

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.

Use of 10-valent pneumococcal conjugate vaccine in Kenya has led to substantial reductions in vaccine-type pneumococcal carriage and invasive pneumococcal disease. However, analysis of recent surveillance data indicates an outbreak of vaccine-type serotype 1 in 2023 in Kibera, Kenya. Continued monitoring of invasive pneumococcal disease in Kenya is warranted.

Indirect immunofluorescence antibody assays have been the primary method for laboratory diagnosis of ehrlichiosis. Detection of Ehrlichia spp. DNA by using PCR is now widely available through commercial laboratories. To prepare for Ehrlichia spp. PCR introduction, we assessed ehrlichiosis testing practices, quantified the proportion of samples eligible for PCR testing, and estimated the potential effect of implementing PCR at the University of North Carolina health system in North Carolina, USA, which is in an area with a high-incidence of ehrlichiosis. We found <1% of patient samples underwent PCR testing, even though rates of serodiagnostic algorithm completion (testing of acute and convalescent samples) were low (18.4%). Our findings show a need to educate providers on diagnostic and treatment guidelines for ehrlichiosis and raise awareness of the availability and advantage of PCR testing.

During 2020-2023, we sequenced Bayou virus from 2 patients in Louisiana, USA, with hantavirus cardiopulmonary syndrome. Direct virus sequencing demonstrated an inferred evolutionary relationship to previous cases. Our findings demonstrate that separate virus spillovers cause isolated cases and probable wide distribution of Bayou hantavirus in rodents across Louisiana.

Vancomycin-resistant Staphylococcus aureus (VRSA) is a rare but serious public health concern. We describe a VRSA case in North Carolina, USA. The isolate from the case belonged to the USA600 lineage and clonal complex 45. No transmission was identified. Confirmed VRSA cases should include a thorough investigation and public health response.

Reports of mpox are rising in Africa where the disease is endemic and in new countries where the disease has not been previously seen. The 2022 global outbreak of clade II mpox and an ongoing outbreak of the more lethal clade I mpox highlight the pandemic potential for monkeypox virus. Waning population immunity after the cessation of routine immunization for smallpox plays a key role in the changing epidemiologic patterns of mpox. Sustained human-to-human transmission of mpox is occurring widely in the context of insufficient population immunity, fueling genetic mutations that affect the accuracy of some diagnostic tests and that could lead to changing virulence. Additional research should address complex challenges for control of mpox, including improved diagnostics and medical countermeasures. The availability of vaccines should be expanded not only for outbreak response but also for broader routine use for persons in mpox-endemic countries.

Neisseria meningitidis is a common commensal bacterium of the nasopharynx that can cause invasive meningococcal disease (IMD). In comparison, N. gonorrhoeae is always a pathogen usually limited to mucosal sites. However, increased evidence for overlapping clinical syndromes is emerging. We compared N. meningitidis samples from a urogenital outbreak in Australia with sequences from the United States and other countries. We conducted phylogenetic analyses to assess relatedness and examine for genomic changes associated with meningococcal adaptation; we collated a total of 255 serogroup Y (MenY), sequence type (ST) 1466 isolate assemblies. Most urogenital isolates originated from Australia; those isolates formed a distinct clade, most closely related genomically to recent US IMD isolates. No specific genomic changes suggested niche adaptation or associated clinical manifestations. The MenY ST1466 N. meningitidis isolates circulating in Australia and the United States are capable of causing both urethritis and invasive meningococcal disease.

Evolving technology and the development of new devices that can aerosolize water present a risk for new sources of Legionella bacteria growth and spread within industrial settings. We investigated a cluster of legionellosis among employees of a manufacturing facility in South Carolina, USA, and found 2 unique equipment sources of Legionella bacteria. The cluster of cases took place during August-November 2022; a total of 34 cases of legionellosis, including 15 hospitalizations and 2 deaths, were reported. Legionella pneumophila was isolated from 3 devices: 2 water jet cutters and 1 floor scrubber. L. pneumophila sequence type 36 was identified in environmental isolates and 1 patient specimen, indicating that those devices were the likely source of infection. Remediation was ultimately achieved through the development and implementation of a device-specific water management program. Manufacturing facilities that use aerosol-generating devices should consider maintaining updated Legionella water management programs to prevent Legionella bacterial infections.

Event management systems (EMS) are key tools for epidemic intelligence, integrating surveillance signals and incident response, although international standards to inform development are lacking. We describe the Nigeria Centre for Disease Control and Prevention (NCDC) SITAware, a software capable of operating with low internet bandwidth to generate notifications, reports, and spatiotemporal dashboards and provide event-level data for real-time accountability and postevent learning. SITAware was enabled by local institutional ownership, co-created at low cost, and integrated into existing workflows. In 2022, SITAware was used to manage ≈300 incidents, and NCDC implemented it subnationally. NCDC's experience may inform EMS development and implementation in similar settings.

Bartonella quintana infection can cause severe disease that includes clinical manifestations such as endocarditis, chronic bacteremia, and vasoproliferative lesions of the skin and viscera. B. quintana bacteria is transmitted by the human body louse (Pediculus humanus corporis) and is associated with homelessness and limited access to hygienic services. We report B. quintana infection in 2 kidney transplant recipients in the United States from an organ donor who was experiencing homelessness. One infection manifested atypically, and the other was minimally symptomatic; with rapid detection, both recipients received timely treatment and recovered. B. quintana was identified retrospectively in an archived donor hematoma specimen, confirming the transmission link. Information about the organ donor's housing status was critical to this investigation. Evaluation for B. quintana infection should be considered for solid organ transplant recipients who receive organs from donors with a history of homelessness or of body lice infestation.

Louseborne Bartonella quintana infections in the United States occur almost exclusively among persons experiencing homelessness because of inadequate access to hygiene resources. Homelessness is increasing, and persons experiencing homelessness can be organ donors, despite barriers to receiving donated organs themselves. Recent reports have documented B. quintana transmission via organs transplanted from donors who had recently experienced homelessness. Those reports demonstrate the threat of severe bartonellosis in immunosuppressed organ transplant recipients after donor-derived B. quintana infection. Addressing the root causes of B. quintana transmission could improve the quality of life for persons experiencing homelessness and simultaneously mitigate risk for donor-derived B. quintana transmission. Interventions include improved access to housing, consistent access to hot water for showers and laundry, early treatment of body lice infestation and B. quintana infection, and B. quintana testing and prophylactic treatment of recipients of organs from donors who have experienced risk factors for B. quintana, including homelessness.

Bartonella quintana infection can lead to bacillary angiomatosis, peliosis hepatis, chronic bacteremia, and culture-negative endocarditis. Transmitted by the human body louse (Pediculus humanus humanus), B. quintana infection has become an emerging disease in recent decades among persons experiencing homelessness. By using retrospective laboratory surveillance, we identified 5 cases of left-sided, culture-negative B. quintana endocarditis among persons in New York, New York, USA, during January 1, 2020-November 23, 2023. Identifications were made by using molecular assays. All patients experienced unsheltered homelessness in the year before hospitalization. Of those patients, 4 experienced heart failure, 3 renal failure, and 2 embolic strokes; 2 died. Aortic valve replacement occurred in 4 cases. A history of possible body louse infestation was found in 4 cases. Clinicians should consider housing status and history of lice exposure in patients with suspected bartonellosis and have a low threshold for diagnostic testing and empiric treatment in patients experiencing homelessness.

The 2014 chikungunya outbreak in the Dominican Republic resulted in intense local transmission, with high postoutbreak seroprevalence. The resulting population immunity will likely minimize risk for another large outbreak through 2035, but changes in population behavior or environmental conditions or emergence of different virus strains could lead to increased transmission.

In a US survey of infectious disease specialists, 61 respondents reported seeing >1 Bartonella quintana infection during 2014-2024. Diagnostic challenges included limited healthcare provider awareness, inadequate testing, and inconsistent healthcare access among affected populations. Early recognition of B. quintana infections is needed to improve outcomes among affected populations.

International pet travel and commercial operations have increased animal disease importation risks, including for Leishmania infantum, a deadly parasite of humans and domestic dogs. Collaborating as an interdisciplinary working group, we developed an operational tool for veterinary and public health practitioners to assess and manage L. infantum risk in dogs imported to the United States. Overall risk varies by dog, human, and geographic factors but could be high without proper controls. We determined dog risk management strategies should include application of sand fly insecticides and repellents, sterilization, and treatment. US public health authorities can use a One Health approach to manage L. infantum importation risks via infected dogs.

We report 2 canine cases of carbapenemase-producing Pseudomonas aeruginosa within a United States veterinary hospital associated with a human outbreak linked to over-the-counter artificial tears. We investigated veterinary hospital transmission. Veterinary antimicrobial resistance surveillance and infection prevention and control enhancements are needed to reduce transmission of carbapenemase-producing organisms.

We investigated a blastomycosis cluster among humans and canines in a neighborhood in Wisconsin, United States. We conducted interviews and collected serum specimens for Blastomyces antibody testing by enzyme immunoassay. Although no definitive exposure was identified, evidence supports potential exposures from the riverbank, riverside trails or yards, or construction dust.

We report a patient in North Carolina, USA, with Heartland virus infection whose diagnosis was complicated by previous Ehrlichia chaffeensis infection. We identified E. ewingii-infected and Bourbon virus-infected tick pools at the patient's residence. Healthcare providers should consider testing for tickborne viruses if ehrlichiosis is suspected.

Wastewater testing can inform public health action as a component of polio outbreak response. During 2022-2023, a total of 7 US jurisdictions (5 states and 2 cities) participated in prospective or retrospective testing of wastewater for poliovirus after a paralytic polio case was identified in New York state. Two distinct vaccine-derived poliovirus type 2 viruses were detected in wastewater from New York state and New York City during 2022, representing 2 separate importation events. Of those viruses, 1 resulted in persistent community transmission in multiple New York counties and 1 paralytic case. No poliovirus was detected in the other participating jurisdictions (Connecticut, New Jersey, Michigan, and Illinois and Chicago, IL). The value of routine wastewater surveillance for poliovirus apart from an outbreak is unclear. However, these results highlight the ongoing risk for poliovirus importations into the United States and the need to identify undervaccinated communities and increase vaccination coverage to prevent paralytic polio.

Congregate homeless shelters are disproportionately affected by infectious disease outbreaks. We describe enterovirus epidemiology across 23 adult and family shelters in King County, Washington, USA, during October 2019-May 2021, by using repeated cross-sectional respiratory illness and environmental surveillance and viral genome sequencing. Among 3,281 participants >3 months of age, we identified coxsackievirus A21 (CVA21) in 39 adult residents (3.0% [95% CI 1.9%-4.8%] detection) across 7 shelters during October 2019-February 2020. We identified enterovirus D68 (EV-D68) in 5 adult residents in 2 shelters during October-November 2019. Of 812 environmental samples, 1 was EV-D68-positive and 5 were CVA21-positive. Other enteroviruses detected among residents, but not in environmental samples, included coxsackievirus A6/A4 in 3 children. No enteroviruses were detected during April 2020-May 2021. Phylogenetically clustered CVA21 and EV-D68 cases occurred in some shelters. Some shelters also hosted multiple CVA21 lineages.

In Kenya, influenza virus circulates year-round, raising questions about optimum strategies for vaccination. Given national interest in introducing influenza vaccination for young children 6-23 months of age, we modeled total influenza-associated illnesses (inclusive of hospitalizations, outpatient illnesses, and non‒medically attended illnesses) averted by multiple potential vaccination strategies: year-round versus seasonal-campaign vaccination, and vaccination starting in April (Southern Hemisphere influenza vaccine availability) versus October (Northern Hemisphere availability). We modeled average vaccine effectiveness of 50% and annual vaccination coverage of 60%. In the introduction year, year-round vaccination averted 6,410 total illnesses when introduced in October and 7,202 illnesses when introduced in April, whereas seasonal-campaign vaccination averted 10,236 (October) to 11,612 (April) illnesses. In the year after introduction, both strategies averted comparable numbers of illnesses (10,831-10,868 for year-round, 10,175-11,282 for campaign). Campaign-style vaccination would likely have a greater effect during initial pediatric influenza vaccine introduction in Kenya; however, either strategy could achieve similar longer-term effects.

We studied SARS-CoV-2 binding and neutralizing antibody titers among previously infected persons in the United States over time. We assayed SARS-CoV-2 spike protein receptor-binding domain and neutralizing antibody titers for a convenience sample of residual clinical serum specimens that had evidence of prior SARS-CoV-2 infection gathered during January 2021-February 2022. We correlated titers and examined them by age group (<18, 18-49, 50-64, and >65 years) across 4 different SARS-CoV-2 variant epochs. Among selected specimens, 30,967 had binding antibody titers and 744 had neutralizing titers available. Titers in specimens from children and adults correlated. In addition, mean binding antibody titers increased over time for all age groups, and mean neutralization titers increased over time for persons 16-49 and >65 years of age. Incorporating binding and neutralization antibody titers into infectious disease surveillance could provide a clearer picture of overall immunity and help target vaccination campaigns.

Rocky Mountain spotted fever (RMSF) is a severe tickborne disease that can reach epidemic proportions in communities with certain social and ecologic risk factors. In some areas, the case-fatality rate of brown dog tick-associated RMSF is up to 50%. Because of the spread of brown dog tick-associated RMSF in the southwestern United States and northern Mexico, the disease has the potential to emerge and become endemic in other communities that have large populations of free-roaming dogs, brown dog ticks, limited resources, and low provider awareness of the disease. By using a One Health approach, interdisciplinary teams can identify communities at risk and prevent severe or fatal RMSF in humans before cases occur. We have developed a conceptual framework for RMSF prevention to enable communities to identify their RMSF risk level and implement prevention and control strategies.