SAN DIEGO — Researchers from the New York City Department of Health and Mental Hygiene discovered that a cooling tower was the source of the 2014-2015 outbreak of legionnaires' disease in a 60,000-resident housing complex in New York City.
By using PCR in combination with culture, the researchers said they were able to take action to prevent further illness 5 days earlier than if they had used culture alone.
“For environmental specimens, bacterial culture is the gold standard for Legionella detection. It can confirm viable organisms and identify the subgroup, but results can take 1–2 weeks, potentially limiting action,” Isaac Benowitz, MD, medical epidemiologist at the New York City Department of Health and Mental Hygiene, and colleagues wrote. “PCR of environmental samples for Legionella pneumophila was a valuable tool for rapidly identifying the source during an escalating outbreak, and allowed us to take rapid action.”
According to Benowitz, the rate of legionnaire’s disease (LD) in New York City has risen from 0.8 cases per 100,000 population in 2002 to 2.7 cases per 100,000 population in 2009. The researchers investigated a cluster of nine LD cases who lived in or had visited the South Bronx housing complex and became ill between November 2014 and January 2015. All patients were diagnosed by urine antigen test. Possible sources of the disease were identified through case patient interviews, visits to the housing area and from a partial list of the city’s cooling towers. The researchers also identified cooling towers using Google Earth aerial photography. Water and and swab samples were collected and tested using PCR and then culture. Legionella pneumophila serogroup 1, or Lp1, isolated in sputum, was matched by PCR in samples from an industrial cooling tower at a power plant, which took 2 days to complete. The researchers confirmed their results with culture 5 days later.
A recent change in biocide disinfectant in the cooling tower may have led to the outbreak, according to Benowitz and colleagues.
“Legionnaires' disease is a cause of severe community-acquired pneumonia,” they wrote. “LD outbreaks have been caused by cooling towers, decorative fountains, hot tubs and hot water systems.” – by Will Offit
Benowitz I, et al. Abstract 257. Presented at: IDWeek; Oct. 7-11, 2015; San Diego.
Disclosure: The researchers report no relevant financial disclosures.