Surveillance for Multisystem Inflammatory Syndrome in US Children Aged 5-11 Years Who Received Pfizer-BioNTech COVID-19 Vaccine, November 2021 through March 2022.

Multisystem inflammatory syndrome in children (MIS-C) is a complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection; in the United States, reporting of MIS-C after coronavirus disease 2019 (COVID-19) vaccination is required for vaccine safety monitoring. Pfizer-BioNTech COVID-19 vaccine was authorized for children aged 5-11 years on 29 October 2021. Covering a period when approximately 7 million children received vaccine, surveillance for MIS-C ≤ 90 days postvaccination using passive systems identified 58 children with MIS-C and laboratory evidence of past/recent SARS-CoV-2 infection, and 4 without evidence. During a period with extensive SARS-CoV-2 circulation, MIS-C illness in children after COVID-19 vaccination who lacked evidence of SARS-CoV-2 infection was rare (<1 per million vaccinated children).

Overseas Treatment of Latent Tuberculosis Infection in US-Bound Immigrants.

Seventy percent of tuberculosis (TB) cases in the United States occur among non-US-born persons; cases usually result from reactivation of latent TB infection (LTBI) likely acquired before the person's US arrival. We conducted a prospective study among US immigrant visa applicants undergoing the required overseas medical examination in Vietnam. Consenting applicants >15 years of age were offered an interferon-γ release assay (IGRA); those 12-14 years of age received an IGRA as part of the required examination. Eligible participants were offered LTBI treatment with 12 doses of weekly isoniazid and rifapentine. Of 5,311 immigrant visa applicants recruited, 2,438 (46%) consented to participate; 2,276 had an IGRA processed, and 484 (21%) tested positive. Among 452 participants eligible for treatment, 304 (67%) initiated treatment, and 268 (88%) completed treatment. We demonstrated that using the overseas medical examination to provide voluntary LTBI testing and treatment should be considered to advance US TB elimination efforts.

Characteristics and Clinical Outcomes of Children and Adolescents Aged <18 Years Hospitalized with COVID-19 - Six Hospitals, United States, July-August 2021.

During June 2021, the highly transmissible† B.1.617.2 (Delta) variant of SARS-CoV-2, the virus that causes COVID-19, became the predominant circulating strain in the United States. U.S. pediatric COVID-19-related hospitalizations increased during July-August 2021 following emergence of the Delta variant and peaked in September 2021.§ As of May 12, 2021, CDC recommended COVID-19 vaccinations for persons aged ≥12 years,¶ and on November 2, 2021, COVID-19 vaccinations were recommended for persons aged 5-11 years.** To date, clinical signs and symptoms, illness course, and factors contributing to hospitalizations during the period of Delta predominance have not been well described in pediatric patients. CDC partnered with six children's hospitals to review medical record data for patients aged <18 years with COVID-19-related hospitalizations during July-August 2021.†† Among 915 patients identified, 713 (77.9%) were hospitalized for COVID-19 (acute COVID-19 as the primary or contributing reason for hospitalization), 177 (19.3%) had incidental positive SARS-CoV-2 test results (asymptomatic or mild infection unrelated to the reason for hospitalization), and 25 (2.7%) had multisystem inflammatory syndrome in children (MIS-C), a rare but serious inflammatory condition associated with COVID-19.§§ Among the 713 patients hospitalized for COVID-19, 24.7% were aged <1 year, 17.1% were aged 1-4 years, 20.1% were aged 5-11 years, and 38.1% were aged 12-17 years. Approximately two thirds of patients (67.5%) had one or more underlying medical conditions, with obesity being the most common (32.4%); among patients aged 12-17 years, 61.4% had obesity. Among patients hospitalized for COVID-19, 15.8% had a viral coinfection¶¶ (66.4% of whom had respiratory syncytial virus [RSV] infection). Approximately one third (33.9%) of patients aged <5 years hospitalized for COVID-19 had a viral coinfection. Among 272 vaccine-eligible (aged 12-17 years) patients hospitalized for COVID-19, one (0.4%) was fully vaccinated.*** Approximately one half (54.0%) of patients hospitalized for COVID-19 received oxygen support, 29.5% were admitted to the intensive care unit (ICU), and 1.5% died; of those requiring respiratory support, 14.5% required invasive mechanical ventilation (IMV). Among pediatric patients with COVID-19-related hospitalizations, many had severe illness and viral coinfections, and few vaccine-eligible patients hospitalized for COVID-19 were vaccinated, highlighting the importance of vaccination for those aged ≥5 years and other prevention strategies to protect children and adolescents from COVID-19, particularly those with underlying medical conditions.

Impact of Effective Global Tuberculosis Control on Health and Economic Outcomes in the United States.

Rationale: Most U.S. residents who develop tuberculosis (TB) were born abroad, and U.S. TB incidence is increasingly driven by infection risks in other countries.Objectives: To estimate the potential impact of effective global TB control on health and economic outcomes in the United States.Methods: We estimated outcomes using linked mathematical models of TB epidemiology in the United States and migrants' birth countries. A base-case scenario extrapolated country-specific TB incidence trends. We compared this with scenarios in which countries achieve 90% TB incidence reductions between 2015 and 2035, as targeted by the World Health Organization's End TB Strategy ("effective global TB control"). We also considered pessimistic scenarios of flat TB incidence trends in individual countries.Measurements and Main Results: We estimated TB cases, deaths, and costs and the total economic burden of TB in the United States. Compared with the base-case scenario, effective global TB control would avert 40,000 (95% uncertainty interval, 29,000-55,000) TB cases in the United States in 2020-2035. TB incidence rates in 2035 would be 43% (95% uncertainty interval, 34-54%) lower than in the base-case scenario, and 49% (95% uncertainty interval, 44-55%) lower than in 2020. Summed over 2020-2035, this represents 0.8 billion dollars (95% uncertainty interval, 0.6-1.0 billion dollars) in averted healthcare costs and $2.5 billion dollars (95% uncertainty interval, 1.7-3.6 billion dollars) in productivity gains. The total U.S. economic burden of TB (including the value of averted TB deaths) would be 21% (95% uncertainty interval, 16-28%) lower (18 billion dollars [95% uncertainty level, 8-32 billion dollars]).Conclusions: In addition to producing major health benefits for high-burden countries, strengthened efforts to achieve effective global TB control could produce substantial health and economic benefits for the United States.

The Predictive Performance of a Pneumonia Severity Score in Human Immunodeficiency Virus-negative Children Presenting to Hospital in 7 Low- and Middle-income Countries.

BACKGROUND: In 2015, pneumonia remained the leading cause of mortality in children aged 1-59 months. METHODS: Data from 1802 human immunodeficiency virus (HIV)-negative children aged 1-59 months enrolled in the Pneumonia Etiology Research for Child Health (PERCH) study with severe or very severe pneumonia during 2011-2014 were used to build a parsimonious multivariable model predicting mortality using backwards stepwise logistic regression. The PERCH severity score, derived from model coefficients, was validated on a second, temporally discrete dataset of a further 1819 cases and compared to other available scores using the C statistic. RESULTS: Predictors of mortality, across 7 low- and middle-income countries, were age <1 year, female sex, ≥3 days of illness prior to presentation to hospital, low weight for height, unresponsiveness, deep breathing, hypoxemia, grunting, and the absence of cough. The model discriminated well between those who died and those who survived (C statistic = 0.84), but the predictive capacity of the PERCH 5-stratum score derived from the coefficients was moderate (C statistic = 0.76). The performance of the Respiratory Index of Severity in Children score was similar (C statistic = 0.76). The number of World Health Organization (WHO) danger signs demonstrated the highest discrimination (C statistic = 0.82; 1.5% died if no danger signs, 10% if 1 danger sign, and 33% if ≥2 danger signs). CONCLUSIONS: The PERCH severity score could be used to interpret geographic variations in pneumonia mortality and etiology. The number of WHO danger signs on presentation to hospital could be the most useful of the currently available tools to aid clinical management of pneumonia.

Colonization Density of the Upper Respiratory Tract as a Predictor of Pneumonia-Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Pneumocystis jirovecii.

BACKGROUND.: There is limited information on the association between colonization density of upper respiratory tract colonizers and pathogen-specific pneumonia. We assessed this association for Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Pneumocystis jirovecii. METHODS.: In 7 low- and middle-income countries, nasopharyngeal/oropharyngeal swabs from children with severe pneumonia and age-frequency matched community controls were tested using quantitative polymerase chain reaction (PCR). Differences in median colonization density were evaluated using the Wilcoxon rank-sum test. Density cutoffs were determined using receiver operating characteristic curves. Cases with a pathogen identified from lung aspirate culture or PCR, pleural fluid culture or PCR, blood culture, and immunofluorescence for P. jirovecii defined microbiologically confirmed cases for the given pathogens. RESULTS.: Higher densities of H. influenzae were observed in both microbiologically confirmed cases and chest radiograph (CXR)-positive cases compared to controls. Staphylococcus aureus and P. jirovecii had higher densities in CXR-positive cases vs controls. A 5.9 log10 copies/mL density cutoff for H. influenzae yielded 86% sensitivity and 77% specificity for detecting microbiologically confirmed cases; however, densities overlapped between cases and controls and positive predictive values were poor (<3%). Informative density cutoffs were not found for S. aureus and M. catarrhalis, and a lack of confirmed case data limited the cutoff identification for P. jirovecii. CONCLUSIONS.: There is evidence for an association between H. influenzae colonization density and H. influenzae-confirmed pneumonia in children; the association may be particularly informative in epidemiologic studies. Colonization densities of M. catarrhalis, S. aureus, and P. jirovecii are unlikely to be of diagnostic value in clinical settings.

Infective endocarditis in northeastern Thailand.

Despite rigorous diagnostic testing, the cause of infective endocarditis was identified for just 60 (45.5%) of 132 patients admitted to hospitals in Khon Kaen, Thailand, during January 2010-July 2012. Most pathogens identified were Viridans streptococci and zoonotic bacteria species, as found in other resource-limited countries where underlying rheumatic heart disease is common.

Hospitalizations for acute lower respiratory tract infection due to respiratory syncytial virus in Thailand, 2008-2011.

BACKGROUND: Few population-based estimates of the incidence of respiratory syncytial virus (RSV) infection in low- or middle-income countries are available. We describe the incidence and epidemiology of hospitalizations for RSV-associated acute lower respiratory tract infection (ALRI) detected by active population-based surveillance in 2 rural Thailand provinces during 2008-2011. METHODS: Patients hospitalized with ALRI were systematically sampled. Consenting patients provided nasopharyngeal swab specimens for RSV testing by real-time reverse-transcription polymerase chain reaction. RESULTS: Of 13 982 enrolled patients hospitalized with ALRI, 1137 (8.1%) were RSV positive. After adjustment for sampling and nonenrollment, the incidence of RSV-associated ALRI hospitalization was 85 cases per 100,000 persons/year. The highest rates occurred among children aged <5 years (981 cases per 100,000 persons/year) and <1 year (1543 cases per 100,000 persons/year). Rates were low among older children and young adults but high among persons aged >65 years (130 cases per 100,000 persons/year). Eight (0.7%) RSV-infected study patients died during hospitalization. Annual RSV hospitalizations peaked during July-October with almost no documented RSV hospitalizations during January-June. CONCLUSIONS: Our findings demonstrate the substantial contribution of RSV to global ALRI burden, especially in children aged <5 years and the elderly, and underscore the urgent need for effective prevention measures.

Pediatric Tuberculosis: A Review of Evidence-Based Best Practices for Clinicians and Health Care Providers.

Advances in pediatric TB care are promising, the result of decades of advocacy, operational and clinical trials research, and political will by national and local TB programs in high-burden countries. However, implementation challenges remain in linking policy to practice and scaling up innovations for prevention, diagnosis, and treatment of TB in children, especially in resource-limited settings. There is both need and opportunity to strengthen clinician confidence in making a TB diagnosis and managing the various manifestations of TB in children, which can facilitate the translation of evidence to action and expand access to new tools and strategies to address TB in this population. This review aims to summarize existing guidance and best practices for clinicians and health care providers in low-resource, TB-endemic settings and identify resources with more detailed and actionable information for decision-making along the clinical cascade to prevent, find, and cure TB in children.

COVID-19 Vaccine Safety First Year Findings in Adolescents.

BACKGROUND AND OBJECTIVES: The Food and Drug Administration expanded Emergency Use Authorization for use of Pfizer-BioNTech (BNT-162b2) coronavirus disease 2019 vaccine to include people ages 12 years and older on May 10, 2021. We describe adverse events observed during the first full year of the US coronavirus disease 2019 vaccination program for adolescents ages 12 to 17 years. METHODS: We conducted descriptive analyses using data from 2 complementary US vaccine safety monitoring systems: v-safe, a voluntary smartphone-based system that monitors reactions and health impacts, and the Vaccine Adverse Event Reporting System (VAERS), the national spontaneous reporting system. We reviewed reports and calculated adverse event reporting rates using vaccine administration data. RESULTS: Among 172 032 adolescents ages 12 to 17 years enrolled in v-safe, most reported reactions following BNT-162b2 were mild to moderate, most frequently reported on the day after vaccination, and more common after dose 2. VAERS received 20 240 adverse event reports; 91.5% were nonserious. Among adverse events of interest, we verified 40 cases of multisystem inflammation syndrome in children (1.2 cases per million vaccinations), 34 (85%) of which had evidence of prior severe acute respiratory syndrome coronavirus 2 infection; and 570 cases of myocarditis (17.7 cases per million vaccinations), most of whom (77%) reported symptom resolution at the time of report. CONCLUSIONS: During the first year BNT-162b2 was administered to adolescents ages 12 to 17 years, most reported adverse events were mild and appeared self-limited. Rates of myocarditis were lower than earlier reports. No new serious safety concerns were identified.

High prevalence of cryptococcal infection among HIV-infected patients hospitalized with pneumonia in Thailand.

BACKGROUND: Cryptococcal meningitis (CM) is a major cause of death among HIV-infected patients. Cryptococcal antigenemia (CrAg+) in the absence of CM can represent early-stage cryptococcosis during which antifungal treatment might improve outcomes. However, patients without meningitis are rarely tested for cryptococcal infection. We evaluated Cryptococcus species as a cause of acute respiratory infection in hospitalized patients in Thailand and evaluated clinical characteristics associated with CrAg+. METHODS: We tested banked serum samples from 704 human immunodeficiency virus (HIV)-infected and 730 HIV-uninfected patients hospitalized with acute respiratory infection from 2004 through 2009 in 2 rural provinces in Thailand for the presence of CrAg+. Retrospective chart reviews were conducted for CrAg+ patients to distinguish meningeal and nonmeningeal cryptococcosis and to identify clinical characteristics associated with CrAg+ in patients with and without evidence of CM. RESULTS: CrAg+ was found in 92 HIV-infected patients (13.1%); only tuberculosis (19.3%) and rhinovirus (16.5%) were identified more frequently. No HIV-uninfected patients were CrAg+. Of 70 CrAg+ patients with medical charts available, 37 (52.9%) had no evidence of past or existing CM at hospitalization; 30 of those patients (42.9% of all CrAg+) had neither past nor existing CM, nor any alternate etiology of infection identified. Dyspnea was more frequent among CrAg+ patients without CM than among CrAg- patients (P = .0002). CONCLUSIONS: Cryptococcus species were the most common pathogens detected in HIV-infected patients hospitalized with acute respiratory infection in Thailand. Few clinical differences were found between antigenemic and nonantigenemic HIV-infected patients. Health care providers in Thailand should evaluate HIV-infected patients hospitalized with acute respiratory infection for cryptococcal antigenemia, even in the absence of meningitis.

The Pneumonia Etiology Research for Child Health Project: a 21st century childhood pneumonia etiology study.

The Pneumonia Etiology Research for Child Health (PERCH) project is a 7-country, standardized, comprehensive evaluation of the etiologic agents causing severe pneumonia in children from developing countries. During previous etiology studies, between one-quarter and one-third of patients failed to yield an obvious etiology; PERCH will employ and evaluate previously unavailable innovative, more sensitive diagnostic techniques. Innovative and rigorous epidemiologic and analytic methods will be used to establish the causal association between presence of potential pathogens and pneumonia. By strategic selection of study sites that are broadly representative of regions with the greatest burden of childhood pneumonia, PERCH aims to provide data that reflect the epidemiologic situation in developing countries in 2015, using pneumococcal and Haemophilus influenzae type b vaccines. PERCH will also address differences in host, environmental, and/or geographic factors that might determine pneumonia etiology and, by preserving specimens, will generate a resource for future research and pathogen discovery.

Lessons learned from influenza A(H1N1)pdm09 pandemic response in Thailand.

In 2009, Thailand experienced rapid spread of the pandemic influenza A(H1N1)pdm09 virus. The national response came under intense public scrutiny as the number of confirmed cases and associated deaths increased. Thus, during July-December 2009, the Ministry of Public Health and the World Health Organization jointly reviewed the response efforts. The review found that the actions taken were largely appropriate and proportionate to need. However, areas needing improvement were surveillance, laboratory capacity, hospital infection control and surge capacity, coordination and monitoring of guidelines for clinical management and nonpharmaceutical interventions, risk communications, and addressing vulnerabilities of non-Thai displaced and migrant populations. The experience in Thailand may be applicable to other countries and settings, and the lessons learned may help strengthen responses to other pandemics or comparable prolonged public health emergencies.

Bartonella vinsonii subsp. arupensis in humans, Thailand.

We identified Bartonella vinsonii subsp. arupensis in pre-enriched blood of 4 patients from Thailand. Nucleotide sequences for transfer-messenger RNA gene, citrate synthase gene, and the 16S-23S rRNA internal transcribed spacer were identical or closely related to those for the strain that has been considered pathogenic since initially isolated from a human in Wyoming, USA.

Overseas screening for tuberculosis in U.S.-bound immigrants and refugees.

BACKGROUND: In 2007, a total of 57.8% of the 13,293 new cases of tuberculosis in the United States were diagnosed in foreign-born persons, and the tuberculosis rate among foreign-born persons was 9.8 times as high as that among U.S.-born persons (20.6 vs. 2.1 cases per 100,000 population). Annual arrivals of approximately 400,000 immigrants and 50,000 to 70,000 refugees from overseas are likely to contribute substantially to the tuberculosis burden among foreign-born persons in the United States. METHODS: The Centers for Disease Control and Prevention (CDC) collects information on overseas screening for tuberculosis among U.S.-bound immigrants and refugees, along with follow-up evaluation after their arrival in the United States. We analyzed screening and follow-up data from the CDC to study the epidemiology of tuberculosis in these populations. RESULTS: From 1999 through 2005, a total of 26,075 smear-negative cases of tuberculosis (i.e., cases in which a chest radiograph was suggestive of active tuberculosis but sputum smears were negative for acid-fast bacilli on 3 consecutive days) and 22,716 cases of inactive tuberculosis (i.e., cases in which a chest radiograph was suggestive of tuberculosis that was no longer clinically active) were diagnosed by overseas medical screening of 2,714,223 U.S.-bound immigrants, representing prevalences of 961 cases per 100,000 persons (95% confidence interval [CI], 949 to 973) and 837 cases per 100,000 persons (95% CI, 826 to 848), respectively. Among 378,506 U.S.-bound refugees, smear-negative tuberculosis was diagnosed in 3923 and inactive tuberculosis in 10,743, representing prevalences of 1036 cases per 100,000 persons (95% CI, 1004 to 1068) and 2838 cases per 100,000 persons (95% CI, 2785 to 2891), respectively. Active pulmonary tuberculosis was diagnosed in the United States in 7.0% of immigrants and refugees with an overseas diagnosis of smear-negative tuberculosis and in 1.6% of those with an overseas diagnosis of inactive tuberculosis. CONCLUSIONS: Overseas screening for tuberculosis with follow-up evaluation after arrival in the United States is a high-yield intervention for identifying tuberculosis in U.S.-bound immigrants and refugees and could reduce the number of tuberculosis cases among foreign-born persons in the United States.

Evidence to Action: Translating Innovations in Management of Child and Adolescent TB into Routine Practice in High-Burden Countries.

Child and adolescent tuberculosis (TB) has been long neglected by TB programs but there have been substantive strides in prioritizing TB among these populations in the past two decades. Yet, gaps remain in translating evidence and policy to action at the primary care level, ensuring access to novel tools and approaches to diagnosis, treatment, and prevention for children and adolescents at risk of TB disease. This article describes the progress that has been made and the gaps that remain in addressing TB among children and adolescents while also highlighting pragmatic approaches and the role of multisectoral partnerships in facilitating integration of innovations into routine program practice.

Multidrug-Resistant Tuberculosis in U.S.-Bound Immigrants and Refugees.

Rationale: Approximately two-thirds of new cases of tuberculosis (TB) in the United States are among non-U.S.-born persons. Culture-based overseas TB screening in U.S.-bound immigrants and refugees has substantially reduced the importation of TB into the United States, but it is unclear to what extent this program prevents the importation of multidrug-resistant TB (MDR-TB). Objectives: To study the epidemiology of MDR-TB in U.S.-bound immigrants and refugees and to evaluate the effect of culture-based overseas TB screening in U.S.-bound immigrants and refugees on reducing the importation of MDR-TB into the United States. Methods: We analyzed data of immigrants and refugees who completed overseas treatment for culture-positive TB during 2015-2019. We also compared mean annual number of MDR-TB cases in non-U.S.-born persons within 1 year of arrival in the United States between 1996-2006 (when overseas screening followed a smear-based algorithm) and 2014-2019 (after full implementation of a culture-based algorithm). Results: Of 3,300 culture-positive TB cases identified by culture-based overseas TB screening in immigrants and refugees during 2015-2019, 122 (3.7%; 95% confidence interval [CI], 3.1-4.1) had MDR-TB, 20 (0.6%; 95% CI, 0.3-0.9) had rifampicin-resistant TB, 382 (11.6%; 95% CI, 10.5-12.7) had isoniazid-resistant TB, and 2,776 (84.1%; 95% CI, 82.9-85.4) had rifampicin- and isoniazid-susceptible TB. None were diagnosed with extensively drug-resistant TB. All 3,300 persons with culture-positive TB completed treatment overseas; of 70 and 11 persons who were treated overseas for MDR-TB and rifampicin-resistant TB, respectively, none were diagnosed with TB disease at postarrival evaluation in the United States. Culture-based overseas TB screening in U.S.-bound immigrants and refugees prevented 24.4 MDR-TB cases per year from arriving in the United States, 18.2 cases more than smear-based overseas TB screening. The mean annual number of MDR-TB cases among non-U.S.-born persons within 1 year of arrival in the United States decreased from 34.6 cases in 1996-2006 to 19.5 cases in 2014-2019 (difference of 15.1; P < 0.001). Conclusions: Culture-based overseas TB screening in U.S.-bound immigrants and refugees substantially reduced the importation of MDR-TB into the United States.

Factors Associated With Severe Illness in Patients Aged <21 Years Hospitalized for COVID-19.

OBJECTIVES: To describe coronavirus disease 2019 (COVID-19)-related pediatric hospitalizations during a period of B.1.617.2 (Δ) variant predominance and to determine age-specific factors associated with severe illness. METHODS: We abstracted data from medical charts to conduct a cross-sectional study of patients aged <21 years hospitalized at 6 United States children's hospitals from July to August 2021 for COVID-19 or with an incidental positive severe acute respiratory syndrome coronavirus 2 test. Among patients with COVID-19, we assessed factors associated with severe illness by calculating age-stratified prevalence ratios (PR). We defined severe illness as receiving high-flow nasal cannula, positive airway pressure, or invasive mechanical ventilation. RESULTS: Of 947 hospitalized patients, 759 (80.1%) had COVID-19, of whom 287 (37.8%) had severe illness. Factors associated with severe illness included coinfection with respiratory syncytial virus (RSV) (PR 3.64) and bacteria (PR 1.88) in infants; RSV coinfection in patients aged 1 to 4 years (PR 1.96); and obesity in patients aged 5 to 11 (PR 2.20) and 12 to 17 years (PR 2.48). Having ≥2 underlying medical conditions was associated with severe illness in patients aged <1 (PR 1.82), 5 to 11 (PR 3.72), and 12 to 17 years (PR 3.19). CONCLUSIONS: Among patients hospitalized for COVID-19, factors associated with severe illness included RSV coinfection in those aged <5 years, obesity in those aged 5 to 17 years, and other underlying conditions for all age groups <18 years. These findings can inform pediatric practice, risk communication, and prevention strategies, including vaccination against COVID-19.

Bartonella seroprevalence in rural Thailand.

We estimated the prevalence of anti-Bartonella antibodies among febrile and non-febrile patients presenting to community hospitals in rural Thailand from February 2002 through March 2003. Single serum specimens were tested for IgG titers to four Bartonella species, B. henselae, B. quintana, B. elizabethae and B. vinsonii subsp vinsonii using an indirect immunofluorescent assay. A titer 21:256 was considered positive. Forty-two febrile patients (9.9%) and 19 non-febrile patients (19%) had positive serology titers to at least one Bartonella species. Age-standardized Bartonella seroprevalence differed significantly between febrile (10%) and non-febrile patients (18%, p=0.047), but did not differ by gender. Among all 521 patients, IgG titers 21:256 to B. henselae were found in 20 participants (3.8%), while 17 (3.3%) had seropositivity to B. quintana, 51 (9.8%) to B. elizabethae, and 19 (3.6%) to B. vinsonii subsp vinsonii. These results suggest exposure to Bartonella species is more common in rural Thailand than previously suspected.