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Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Roisin McElroy reports payment from St. Joseph’s Health Centre/Unity Health Toronto, Toronto, Canada for provision of emergency medical clinical services. Mary-Margaret A. Fill reports receipt of travel funding from the Council of State and Territorial Epidemiologists (CSTE) for travel to CSTE Executive Board meetings and CSTE conference and unpaid service as member-at-large of CSTE’s Executive Board and the University of Tennessee’s One Health Committee. Catherine M. Brown reports receipt of travel support from CSTE for attendance at the CSTE annual conference and unpaid service as a CSTE Executive Board member. No other potential conflicts of interest were disclosed.

Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Kara Mitchell reports the following relationships with the Association of Public Health Laboratories: consultant for a public health–related doctorate program to develop molecular course content, funded travel to national meetings, and a leadership or fiduciary role with the Laboratory Systems and Standards Committee. No other potential conflicts of interest were disclosed.

Background: In 2021, four patients who had received solid organ transplants in the USA developed encephalitis beginning 2-6 weeks after transplantation from a common organ donor. We describe an investigation into the cause of encephalitis in these patients., Methods: From Nov 7, 2021, to Feb 24, 2022, we conducted a public health investigation involving 15 agencies and medical centres in the USA. We tested various specimens (blood, cerebrospinal fluid, intraocular fluid, serum, and tissues) from the organ donor and recipients by serology, RT-PCR, immunohistochemistry, metagenomic next-generation sequencing, and host gene expression, and conducted a traceback of blood transfusions received by the organ donor., Findings: We identified one read from yellow fever virus in cerebrospinal fluid from the recipient of a kidney using metagenomic next-generation sequencing. Recent infection with yellow fever virus was confirmed in all four organ recipients by identification of yellow fever virus RNA consistent with the 17D vaccine strain in brain tissue from one recipient and seroconversion after transplantation in three recipients. Two patients recovered and two patients had no neurological recovery and died. 3 days before organ procurement, the organ donor received a blood transfusion from a donor who had received a yellow fever vaccine 6 days before blood donation., Interpretation: This investigation substantiates the use of metagenomic next-generation sequencing for the broad-based detection of rare or unexpected pathogens. Health-care workers providing vaccinations should inform patients of the need to defer blood donation for at least 2 weeks after receiving a yellow fever vaccine. Despite mitigation strategies and safety interventions, a low risk of transfusion-transmitted infections remains., Funding: US Centers for Disease Control and Prevention (CDC), the Biomedical Advanced Research and Development Authority, and the CDC Epidemiology and Laboratory Capacity Cooperative Agreement for Infectious Diseases., Competing Interests: Declaration of interests LFW received research funding from Accelerate Diagnostics, bioMérieux, Hardy Diagnostics, Roche Molecular Systems, and Selux Diagnostics and honoraria from Roche Molecular Systems, Shionogi, and Talis Biomedical, all unrelated to this work. KSG received research support from ThermoFisher and has a royalty-generating collaborative agreement with ZeptoMetrix, both unrelated to this work. MRW received research grant funding from Roche/Genentech and Novartis and speaking honoraria from Genentech, Novartis, Takeda, and WebMD, all unrelated to this work. CYC received research grant funding from the Bay Area Lyme Disease Foundation and the Chan-Zuckerberg Biohub, unrelated to this work, and is on the scientific advisory board for Mammoth Biosciences, Poppy Health, and BiomeSense. MRW and CYC are consultants and co-founders of Delve Bio. CYC is a co-inventor on US patent 11380421, Pathogen Detection Using Next Generation Sequencing, under which algorithms for taxonomic classification, filtering, and pathogen detection are used by SURPI+ software., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

The earth is rapidly warming, driven by increasing atmospheric carbon dioxide and other gases that result primarily from fossil fuel combustion. In addition to causing arctic ice melting and extreme weather events, climatologic factors are linked strongly to the transmission of many infectious diseases. Changes in the prevalence of infectious diseases not only reflect the impacts of temperature, humidity, and other weather-related phenomena on pathogens, vectors, and animal hosts but are also part of a complex of social and environmental factors that will be affected by climate change, including land use, migration, and vector control. Vector- and waterborne diseases and coccidioidomycosis are all likely to be affected by a warming planet; there is also potential for climate-driven impacts on emerging infectious diseases and antimicrobial resistance. Additional resources for surveillance and public health activities are urgently needed, as well as systematic education of clinicians on the health impacts of climate change., Competing Interests: Potential conflicts of interest. R. H. reports serving as a part-time consultant for the Medical Society Consortium for Climate and Health. P. J. E. reports payment for expert testimony for the Andrews Law Group, Tampa, FL. R. C. L. reports grants from the Centers for Disease Control and Prevention (CDC; U01-CK000633), royalties for chapters from UpToDate, providing editorial services for the CDC Foundation, and is a board member for Greater Boston Physicians for Social Responsibility. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: On 30 January 2020, COVID-19 was declared a Public Health Emergency of International Concern (PHEIC) by the World Health Organization. Almost a month later, on 29 February 2020, the first case in New York City (NYC) was diagnosed., Methods: Three hundred sixty persons with COVID-19-like illness were reported to the NYC Department of Health and Mental Hygiene (DOHMH) before 29 February, but 37 of these tested negative and 237 were never tested for severe acute respiratory syndrome coronavirus 2. Records of 86 persons with confirmed COVID-19 and reported symptom onset prior to 29 February 2020 were reviewed by 4 physician-epidemiologists. Case-patients were classified as possible delayed recognition (PDR) of COVID-19 when upon medical review the reported onset date was believed to reflect the initial symptoms of COVID-19, or insufficient evidence to classify, when the onset could not be determined with confidence. Clinical and epidemiological factors collected by DOHMH and supplemented with emergency department records were analyzed., Results: Thirty-nine PDR COVID-19 cases were identified. The majority had severe disease with 69% presenting to an emergency department within 2 weeks of symptom onset. The first PDR COVID-19 case had symptom onset on 28 January 2020. Only 7 of the 39 cases (18%) had traveled internationally within 14 days of onset (none to China)., Conclusions: COVID-19 was in NYC before being classified as a PHEIC, and eluded surveillance for another month. The delay in recognition limited mitigation efforts; by the time city- and statewide mandates were enacted, 16 and 22 days later, there was already widespread community transmission., Competing Interests: Potential conflicts of interest. B. T. reports grants or contracts from the CDC, outside the submitted work. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

During November 19-21, 2021, an indoor convention (event) in New York City (NYC), was attended by approximately 53,000 persons from 52 U.S. jurisdictions and 30 foreign countries. In-person registration for the event began on November 18, 2021. The venue was equipped with high efficiency particulate air (HEPA) filtration, and attendees were required to wear a mask indoors and have documented receipt of at least 1 dose of a COVID-19 vaccine.* On December 2, 2021, the Minnesota Department of Health reported the first case of community-acquired COVID-19 in the United States caused by the SARS-CoV-2 B.1.1.529 (Omicron) variant in a person who had attended the event (1). CDC collaborated with state and local health departments to assess event-associated COVID-19 cases and potential exposures among U.S.-based attendees using data from COVID-19 surveillance systems and an anonymous online attendee survey. Among 34,541 attendees with available contact information, surveillance data identified test results for 4,560, including 119 (2.6%) persons from 16 jurisdictions with positive SARS-CoV-2 test results. Most (4,041 [95.2%]), survey respondents reported always wearing a mask while indoors at the event. Compared with test-negative respondents, test-positive respondents were more likely to report attending bars, karaoke, or nightclubs, and eating or drinking indoors near others for at least 15 minutes. Among 4,560 attendees who received testing, evidence of widespread transmission during the event was not identified. Genomic sequencing of 20 specimens identified the SARS-CoV-2 B.1.617.2 (Delta) variant (AY.25 and AY.103 sublineages) in 15 (75%) cases, and the Omicron variant (BA.1 sublineage) in five (25%) cases. These findings reinforce the importance of implementing multiple, simultaneous prevention measures, such as ensuring up-to-date vaccination, mask use, physical distancing, and improved ventilation in limiting SARS-CoV-2 transmission, during large, indoor events. † ., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Ruth Lynfield reports unpaid positions as the President of the Council of State and Territorial Epidemiologists and on the National Foundation for Infectious Diseases Executive Board. Ruby Serrano reports honoraria from Ponce Health Sciences University. No other potential conflicts of interest were disclosed.

During 23 October-16 November 2020, the New York City Department of Health and Mental Hygiene investigated coronavirus disease 2019 (COVID-19) outbreaks at 2 construction sites. Challenges in adhering to the New York State Department of Health "Interim COVID-19 Guidance for Construction" were reported. To minimize outbreaks, jurisdictions should increase tailored outreach to the construction industry, emphasizing infection prevention., (Published by Oxford University Press for the Infectious Diseases Society of America 2021.)

Background: Patients colonized with multidrug-resistant Candida auris and discharged to a community setting can subsequently seek care in a different healthcare facility and might be a source of nosocomial transmission of C auris ., Methods: We designed a case management pilot program for a cohort of New York City residents who had a history of positive C auris culture identified during clinical or screening activities in healthcare settings and discharged to a community setting during 2017-2019. Approximately every 3 months, case managers coordinated C auris colonization assessments, which included swabs of groin, axilla, and body sites yielding C auris previously. Patients eligible to become serially negative were those with ≥2 C auris colonization assessments after initial C auris identification. Clinical characteristics of serially negative and positive patients were compared., Results: The cohort included 75 patients. Overall, 45 patients were eligible to become serially negative and had 552 person-months of follow-up. Of these 45 patients, 28 patients were serially negative (62%; rate 5.1/100 person-months), 8 were serially positive, and 9 could not be classified as either. There were no clinical characteristics that were significantly different between serially negative and positive patients. The median time from initial C auris identification to being serially negative at assessments was 8.6 months (interquartile range, 5.7-10.8 months)., Conclusions: A majority of patients, assessed at least twice after C auris identification, no longer had C auris detectable on serial colonization assessments., (© The Author(s) 2020. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

From 2015 to 2017, 11 confirmed brucellosis cases were reported in New York City, leading to 10 Brucella exposure risk events ( Brucella events) in 7 clinical laboratories (CLs). Most patients had traveled to countries where brucellosis is endemic and presented with histories and findings consistent with brucellosis. CLs were not notified that specimens might yield a hazardous organism, as the clinicians did not consider brucellosis until they were notified that bacteremia with Brucella was suspected. In 3 Brucella events, the CLs did not suspect that slow-growing, small Gram-negative bacteria might be harmful. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), which has a limited capacity to identify biological threat agents (BTAs), was used during 4 Brucella events, which accounted for 84% of exposures. In 3 of these incidents, initial staining of liquid media showed Gram-positive rods or cocci, including some cocci in chains, suggesting streptococci. Over 200 occupational exposures occurred when the unknown isolates were manipulated and/or tested on open benches, including by procedures that could generate infectious aerosols. During 3 Brucella events, the CLs examined and/or manipulated isolates in a biological safety cabinet (BSC); in each CL, the CL had previously isolated Brucella Centers for Disease Control and Prevention recommendations to prevent laboratory-acquired brucellosis (LAB) were followed; no seroconversions or LAB cases occurred. Laboratory assessments were conducted after the Brucella events to identify facility-specific risks and mitigations. With increasing MALDI-TOF MS use, CLs are well-advised to adhere strictly to safe work practices, such as handling and manipulating all slow-growing organisms in BSCs and not using MALDI-TOF MS for identification until BTAs have been ruled out., (Copyright © 2020 American Society for Microbiology.)

During 2014-2016, the largest outbreak of Ebola virus disease (EVD) in history occurred in West Africa. The New York City Department of Health and Mental Hygiene (DOHMH) worked with health care providers to prepare for persons under investigation (PUIs) for EVD in New York City. From July 1, 2014, through December 29, 2015, we classified as a PUI a person with EVD-compatible signs or symptoms and an epidemiologic risk factor within 21 days before illness onset. Of 112 persons who met PUI criteria, 74 (66%) sought medical care and 49 (44%) were hospitalized. The remaining 38 (34%) were isolated at home with daily contact by DOHMH staff members. Thirty-two (29%) PUIs received a diagnosis of malaria. Of 10 PUIs tested, 1 received a diagnosis of EVD. Home isolation minimized unnecessary hospitalization. This case study highlights the importance of developing competency among clinical and public health staff managing persons suspected to be infected with a high-consequence pathogen.

On May 24, 2016, the New York City Department of Health and Mental Hygiene notified CDC of two cases of Exophiala dermatitidis bloodstream infections among patients with malignancies who had received care from a single physician at an outpatient oncology facility (clinic A). Review of January 1-May 31, 2016 microbiology records identified E. dermatitidis bloodstream infections in two additional patients who also had received care at clinic A. All four patients had implanted vascular access ports and had received intravenous (IV) medications, including a compounded IV flush solution containing saline, heparin, vancomycin, and ceftazidime, compounded and administered at clinic A.

Background: From December 2013 through May 2014, physicians, dermatopathologists, and public health authorities collaborated to characterize an outbreak of Mycobacterium marinum and other nontuberculous mycobacterial skin and soft tissue infections (SSTIs) associated with handling fish in New York City's Chinatown. Clinicopathologic and laboratory investigations were performed on a series of patients., Methods: Medical records were reviewed for 29 patients. Culture results were available for 27 patients and 24 biopsy specimens were evaluated by histopathology, immunohistochemistry (IHC) staining for acid-fast bacilli (AFB), and mycobacterial polymerase chain reaction (PCR) assays., Results: All patients received antibiotics. The most commonly prescribed antibiotic regimen was clarithromycin and ethambutol. Of the 29 patients in this case series, 16 (55%) received surgical treatment involving incision and drainage, mass excision, and synovectomy. Of these, 7 (44%) had deep tissue involvement. All patients showed improvement. For those with culture results, 11 of 27 (41%) were positive for M. marinum; the remainder showed no growth. Poorly formed granulomas (96%), neutrophils (75%), and necrosis (79%) were found in 24 biopsies. Of 15 cases that were culture-negative and analyzed by other methods, 9 were PCR positive for M. marinum group species, 8 were IHC positive, and 3 were positive by AFB stains., Conclusions: A multidisciplinary approach was used to identify cases in an outbreak of M. marinum infections. The use of histopathology, culture, and IHC plus PCR from full thickness skin biopsy can lead to improved diagnosis of M. marinum SSTIs compared to relying solely on mycobacterial culture, the current gold standard., (Published by Oxford University Press for the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

A patient with no risk factors for malaria was hospitalized in New York City with Plasmodium falciparum infection. After investigating all potential sources of infection, we concluded the patient had been exposed to malaria while hospitalized less than 3 weeks earlier. Molecular genotyping implicated patient-to-patient transmission in a hospital setting. Infect. Control Hosp. Epidemiol. 2015;37(1):113-115.

In late October 2014, Ebola virus disease (Ebola) was diagnosed in a humanitarian aid worker who recently returned from West Africa to New York City (NYC). The NYC Department of Health and Mental Hygiene (DOHMH) actively monitored three close contacts of the patient and 114 health care personnel. No secondary cases of Ebola were detected. In collaboration with local and state partners, DOHMH had developed protocols to respond to such an event beginning in July 2014. These protocols included safely transporting a person at the first report of symptoms to a local hospital prepared to treat a patient with Ebola, laboratory testing for Ebola, and monitoring of contacts. In response to this single case of Ebola, initial health care worker active monitoring protocols needed modification to improve clarity about what types of exposure should be monitored. The response costs were high in both human resources and money: DOHMH alone spent $4.3 million. However, preparedness activities that include planning and practice in effectively monitoring the health of workers involved in Ebola patient care can help prevent transmission of Ebola.

In July 2014, as the Ebola virus disease (Ebola) epidemic expanded in Guinea, Liberia, and Sierra Leone, an air traveler brought Ebola to Nigeria and two American health care workers in West Africa were diagnosed with Ebola and later medically evacuated to a U.S. hospital. New York City (NYC) is a frequent port of entry for travelers from West Africa, a home to communities of West African immigrants who travel back to their home countries, and a home to health care workers who travel to West Africa to treat Ebola patients. Ongoing transmission of Ebolavirus in West Africa could result in an infected person arriving in NYC. The announcement on September 30 of an Ebola case diagnosed in Texas in a person who had recently arrived from an Ebola-affected country further reinforced the need in NYC for local preparedness for Ebola.

A cluster of 5 methicillin-susceptible Staphylococcus aureus infections occurred after administration of methylprednisolone acetate injections in a rheumatology practice. A site visit was conducted to inspect examination rooms, observe techniques, and review charts. The investigation revealed a pervasive lack of aseptic technique that led to multiple opportunities for medication contamination.

Native air sampling (NAS) is distinguished from dedicated air sampling (DAS) devices (eg, BioWatch) that are deployed to detect aerosol disseminations of biological threat agents. NAS uses filter samples from heating, ventilation, and air conditioning (HVAC) systems in commercial properties for environmental sampling after DAS detection of biological threat agent incidents. It represents an untapped, scientifically sound, efficient, widely distributed, and comparably inexpensive resource for postevent environmental sampling. Calculations predict that postevent NAS would be more efficient than environmental surface sampling by orders of magnitude. HVAC filter samples could be collected from pre-identified surrounding NAS facilities to corroborate the DAS alarm and delineate the path taken by the bioaerosol plume. The New York City (NYC) Native Air Sampling Pilot Project explored whether native air sampling would be acceptable to private sector stakeholders and could be implemented successfully in NYC. Building trade associations facilitated outreach to and discussions with property owners and managers, who expedited contact with building managers of candidate NAS properties that they managed or owned. Nominal NAS building requirements were determined; procedures to identify and evaluate candidate NAS facilities were developed; data collection tools and other resources were designed and used to expedite candidate NAS building selection and evaluation in Manhattan; and exemplar environmental sampling playbooks for emergency responders were completed. In this sample, modern buildings with single or few corporate tenants were the best NAS candidate facilities. The Pilot Project successfully demonstrated that in one urban setting a native air sampling strategy could be implemented with effective public-private collaboration.

Background: Long-term care facilities (LTCFs) are vulnerable to outbreaks of influenza. There are limited data on the impact of antiviral chemoprophylaxis on the duration of outbreaks of influenza. We investigated the association of timely initiation of amantadine chemoprophylaxis on the duration and severity of outbreaks of influenza A in LTCFs in New York, New York., Methods: Outbreaks of influenza A occurring from October through May each year during the period 2001-2004 in LTCFs in New York were defined as a single laboratory-confirmed case or a cluster of > or = 2 cases of influenza-like illness on a unit of an LTCF. For those facilities that provided amantadine chemoprophylaxis, we examined the association between the time to initiation of chemoprophylaxis after outbreak onset and duration of outbreak, incidence rate, and case-fatality proportion using simple t tests, multivariate analyses of covariance, and linear regression modeling., Results: Adjusting for influenza season year, facility bed capacity, and the proportion of residents who were vaccinated against influenza, LTCFs that initiated chemoprophylaxis 15 days after outbreak onset (25 facilities) had significantly longer duration of outbreaks (18.3 vs. 6.7 days; P < .001), higher incidence rates (10.5 cases per 100 residents vs. 6.2 cases per 100 residents; P < .023), and higher case-fatality rates (3.3 deaths per 100 residents with influenza A vs. 0.45 deaths per 100 residents with influenza A; P < .005) than did LTCFs that initiated chemoprophylaxis 5 days after outbreak onset (27 facilities)., Conclusions: LTCFs that initiated chemoprophylaxis >5 days after initiation of outbreaks of influenza A had significantly longer outbreaks, significantly higher incidence rates, and significantly higher case-fatality rates. These data support prompt initiation of amantadine chemoprophylaxis after identification of influenza A in LTCFs.

After being notified that 2 high school football teammates from New York City were hospitalized with confirmed or suspected invasive group A streptococcal infections, we conducted an investigation of possible spread among other team members. This investigation highlights a need for guidelines on management of streptococcal and other infectious disease outbreaks in team sport settings.

New York City's first syndromic surveillance systems were established in 1995 to detect outbreaks of waterborne illness. In 1998, daily monitoring of ambulance dispatch calls for influenza-like illness began. After the 2001 World Trade Center attacks, concern about biologic terrorism led to the development of surveillance systems to track chief complaints of patients reporting to emergency departments, over-the-counter and prescription pharmacy sales, and worker absenteeism. These systems have proved useful for detecting substantial citywide increases in common viral illnesses (e.g., influenza, norovirus, and rotavirus). However, the systems have not detected more contained outbreaks earlier than traditional surveillance. Future plans include monitoring school health and outpatient clinic visits, augmenting laboratory testing to confirm syndromic signals, and conducting evaluation studies to identify which of these systems will be continued for the long term.

An outbreak of respiratory illness occurred in a long-term care facility in New York City. Investigation of the outbreak identified confirmed or suspected adenoviral infection in 84% of the residents from October 19 to December 18, 1999. Further identification by type-specific neutralization and restriction analysis identified a new genomic variant of adenovirus type 7.

On October 31, 2001, in New York City, a 61-year-old female hospital employee who had acquired inhalational anthrax died after a 6-day illness. To determine sources of exposure and identify additional persons at risk, the New York City Department of Health, Centers for Disease Control and Prevention, and law enforcement authorities conducted an extensive investigation, which included interviewing contacts, examining personal effects, summarizing patient's use of mass transit, conducting active case finding and surveillance near her residence and at her workplace, and collecting samples from co-workers and the environment. We cultured all specimens for Bacillus anthracis. We found no additional cases of cutaneous or inhalational anthrax. The route of exposure remains unknown. All environmental samples were negative for B. anthracis. This first case of inhalational anthrax during the 2001 outbreak with no apparent direct link to contaminated mail emphasizes the need for close coordination between public health and law enforcement agencies during bioterrorism-related investigations.

The largest reported outbreak of waterborne Escherichia coli O157:H7 in the United States occurred in upstate New York following a county fair in August 1999. Culture methods were used to isolate E. coli O157:H7 from specimens from 128 of 775 patients with suspected infections. Campylobacter jejuni was also isolated from stools of 44 persons who developed diarrheal illness after attending this fair. There was one case of a confirmed coinfection with E. coli O157:H7 and C. jejuni. Molecular detection of stx(1) and stx(2) Shiga toxin genes, immunomagnetic separation (IMS), and selective culture enrichment were utilized to detect and isolate E. coli O157:H7 from an unchlorinated well and its distribution points, a dry well, and a nearby septic tank. PCR for stx(1) and stx(2) was shown to provide a useful screen for toxin-producing E. coli O157:H7, and IMS subculture improved recovery. Pulsed-field gel electrophoresis (PFGE) was used to compare patient and environmental E. coli O157:H7 isolates. Among patient isolates, 117 of 128 (91.5%) were type 1 or 1a (three or fewer bands different). Among the water distribution system isolates, 13 of 19 (68%) were type 1 or 1a. Additionally, PFGE of C. jejuni isolates revealed that 29 of 35 (83%) had indistinguishable PFGE patterns. The PFGE results implicated the water distribution system as the main source of the E. coli O157:H7 outbreak. This investigation demonstrates the potential for outbreaks involving more than one pathogen and the importance of analyzing isolates from multiple patients and environmental samples to develop a better understanding of bacterial transmission during an outbreak.

Two outbreaks of respiratory tract illness associated with prolonged cough occurring in 1998 and 1999 in New York State were investigated. A PCR test for Bordetella pertussis was primarily used by a private laboratory to confirm 680 pertussis cases. Several clinical specimens had positive culture results for B. pertussis during both outbreaks, which confirmed that B. pertussis was circulating during the outbreaks. However, testing by the New York State Department of Health reference laboratory suggested that some of the PCR results may have been falsely positive. In addition, features of the outbreak that suggested that B. pertussis may not have been the primary agent of infection included a low attack rate among incompletely vaccinated children and a significant amount of illness among patients testing PCR negative for B. pertussis. These investigations highlight the importance of appropriate clinical laboratory quality assurance programs, of the limitations of the PCR test, and of interpreting laboratory results in context of clinical disease.