Legionellosis is a severe bacterial infection, most commonly presenting as pneumonia (Legionnaires' Disease), caused by *Legionella* bacteria. It is not contagious person-to-person and primarily affects individuals who inhale contaminated water droplets, especially older adults or those with weakened immune systems.
No active Legionellosis reports in New Hampshire right now.
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Legionellosis first gained widespread recognition following a major outbreak in 1976 at an American Legion convention in Philadelphia, Pennsylvania. The causative bacterium, *Legionella pneumophila*, was identified by the CDC shortly after. This event significantly advanced public health understanding of waterborne diseases and the importance of environmental controls in buildings.
Legionellosis is primarily transmitted through the inhalation of small water droplets (aerosols) containing *Legionella* bacteria. These contaminated aerosols are generated from man-made water systems such as cooling towers, hot tubs, showers, decorative fountains, and large plumbing systems. It is not known to spread directly from person to person.
Contagious Period: Varies by disease
Local health department information and state-specific prevention guidance
Our AI-powered surveillance continuously monitors Legionellosis activity across New Hampshire. We track data from state health departments, local hospitals, CDC reports, and 50+ global health sources to provide early warning of emerging threats.
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For official state health alerts, vaccination locations, and public health guidance specific to New Hampshire, visit your state health department's website.
Whether you live in New Hampshire or are traveling there, knowing the symptoms, timeline, and when to seek care helps you act quickly if exposure occurs.
Seek care if you experience severe dehydration, bloody stools, high fever, or symptoms lasting more than 3 days. Children under 5, adults over 65, and immunocompromised individuals should seek care earlier.
Emergency symptoms: Severe dehydration, inability to keep fluids down for 12 or more hours, or neurological symptoms require emergency care.
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Trusted information from leading health organizations
Official guidance from the U.S. Centers for Disease Control and Prevention
View CDC Resources →Global disease surveillance and guidelines from the World Health Organization
View WHO Resources →Disease information on Virus Watcher is reviewed by our Chief Epidemiologist, a former CDC lead analyst for FluSight forecasting. Outbreak data is aggregated from verified sources including BEACON, ProMED, WHO, CDC, and 50+ national health agencies. This information is for educational purposes and should not replace professional medical advice.
Last reviewed: 2026-07-18
No confirmed cases reported in New Hampshire yet. Here are the latest Legionellosis reports from our global surveillance network.
An ongoing cluster of the illness has sickened 23 people. That's not unusual: Most years, 200 to 700 people in the city are diagnosed with the disease. Faced with an outbreak of Legionnaires' disease on Manhattan's Upper East Side, the Mamdani administration said on Tuesday that…
The New York City Health Department has launched a probe into a concerning cluster of Legionnaires' disease cases along the Upper East Side -- with officials trying to track down the source of the outbreak. Two people have been diagnosed with the potentially fatal pneumonia-like…
This event envelope contains reports on Legionnaires' diseases cases, clusters and outbreaks in the UK. *Source: BEACON* - [View Full Report](https://beaconbio.org/en/event/?eventid=c28ef0cd-53bf-4ec5-875b-e450267fa3e1)
This event envelope contains reports on Legionnaire's disease cases, clusters and outbreaks in Australia. *Source: BEACON* - [View Full Report](https://beaconbio.org/en/event/?eventid=78ef9fa9-8716-4bf8-928b-9d8e425caede)
An unexpected increase in cases of Legionnaires' disease in parts of north-west and south-west London is being investigated by The UK Health Security Agency (UKHSA). Specialists are trying to find out if the cases are linked and to establish the possible source of the disease. …
Tim Fang is a digital producer at CBS Bay Area. A Bay Area native, Tim has been a part of the CBS Bay Area newsroom for more than two decades and joined the digital staff in 2006. A hospital in Santa Clara County is working to find the source of contamination that led to several…
The audio version of this article is generated by AI-based technology. Mispronunciations can occur. We are working with our partners to continually review and improve the results. Hamilton Public Health is investigating several confirmed cases of legionellosis in the city's east…
ST. LOUIS COUNTY, Mo. - An elementary school in the Ritenour School District will remain closed after a teacher there disclosed that she had been hospitalized for Legionnaires' disease during the school year. In separate statements to staff and families in the district and Marvi…
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