Legionella can colonize hospital potable water systems for long periods of time, resulting in an ongoing risk for patients, especially those who are immunocompromised. In this hospital, nosocomial transmission possibly occurred for more than 17 years and was interrupted in 1996, after a sudden increase in incidence led to its recognition. Hospitals specializing in the care of immunocompromised patients (eg, transplant centers) should prioritize surveillance for cases of legionnaires' disease. Aggressive control measures can interrupt transmission of this disease successfully.

Legionella can colonize hospital potable water systems for long periods of time, resulting in an ongoing risk for patients, especially those who are immunocompromised. In this hospital, nosocomial transmission possibly occurred for more than 17 years and was interrupted in 1996, after a sudden increase in incidence led to its recognition. Hospitals specializing in the care of immunocompromised patients (eg, transplant centers) should prioritize surveillance for cases of legionnaires' disease. Aggressive control measures can interrupt transmission of this disease successfully.

From August 1996 through June 1998, 69 ventilated, intensive care unit patients at two Arizona hospitals had nosocomial respiratory tract cultures positive for Burkholderia cepacia. Intrinsically contaminated alcohol-free mouthwash was identified by pulsed-field gel electrophoresis as the source of the outbreak.

Sin Nombre virus (SNV) causes the zoonotic disease hantavirus pulmonary syndrome (HPS). Its mechanisms of transmission from rodent to human are poorly understood. It is possible that specific genetic signature sequences could be used to determine the probable site of each case-patient's exposure. Environmental assessments suggested 12 possible sites of rodent exposure for 6 HPS patients. Rodents were captured at 11 of the 12 sites and screened for SNV infection within 2 weeks of the patient's diagnosis. Viral sequences amplified from tissues of rodents at each site were compared with those from case-patients' tissues. Rodents bearing viruses with genetic sequence identity to case-patients' viruses across 2 genomic segments were identified in 4 investigations but never at >1 site. Indoor exposures to rodents were especially common at implicated sites. By distinguishing among multiple possible sites of exposure, viral genotyping studies can enhance understanding of the conditions associated with infection by SNV.

Differentiating occupational exposure from other potential domestic or recreational exposure(s) for Sin Nombre virus (SNV) infection is an epidemiologic challenge. Interviews on work-related activities were conducted, and serum specimens were obtained from 494 workers in Arizona and New Mexico. These workers may have been exposed to rodents and rodent excreta at work, but their primary occupation did not require rodent contact (National Park Service [n = 193]; Navajo Agricultural Product Industry [n = 65], utility companies [n = 169] and plumbing and heating contractors [n = 67]. Within each occupational group (farm workers [n = 57], laborers [n = 20], professionals [n = 70], repairers [n = 211], service industry workers [n = 83], and technicians [n = 53], the majority of workers reported working in areas that had rodent droppings (range, 75 to 95%); 70% of laborers and 64% of service industry workers reported handling rodents. More than 60% of workers in each group, except technicians, reported reopening and cleaning or working in closed spaces. Approximately 90% of laborers, repairers, and farm workers reported hand-plowing. Although the risk for occupationally related SNV infection appears to be low, workers frequently performed risk activities associated with hantavirus pulmonary syndrome (HPS). All workers were seronegative for SNV by enzyme-linked immunoassay or Western blot testing. These findings, the known occupational exposure of some HPS cases, and the high HPS case-fatality rate (52%) support the need for recommendations to reduce human contact with rodents in the workplace. Increased understanding of hantavirus transmission to humans will help focus future recommendations to minimize human exposures effectively.