Potential Association of Legionnaires' Disease with Hot Spring Water, Hot Springs National Park and Hot Springs, Arkansas, USA, 2018-2019

Legionella pneumophila is the cause of Legionnaires' disease, a life-threatening pneumonia that occurs after inhalation of aerosolized water containing the bacteria. Legionella growth occurs in stagnant, warm-to-hot water (77°F-113°F) that is inadequately disinfected. Piped hot spring water in Hot Springs National Park, Arkansas, USA, has naturally high temperatures (>135°F) that prevent Legionella growth, and Legionnaires' disease has not previously been associated with the park or other hot springs in the United States. During 2018-2019, Legionnaires' disease occurred in 5 persons after they visited the park; 3 of these persons were potentially exposed in spa facilities that used untreated hot spring water. Environmental testing revealed Legionella bacteria in piped spring water, including 134°F stagnant pipe water. These findings underscore the importance of water management programs to reduce Legionella growth in plumbing through control activities such as maintaining hot water temperatures, reducing stored water age, and ensuring adequate water flow.

Mumps in a highly vaccinated Marshallese community in Arkansas, USA: an outbreak report

BACKGROUND

During 2000-15, Arkansas Department of Health, Little Rock, AR, USA, investigated between one and six cases of mumps each year. From Aug 5, 2016, to Aug 5, 2017, the department received notification of more than 4000 suspected mumps cases in the second largest outbreak in the USA in the past 30 years.

METHODS

Arkansas Department of Health investigated all reported cases of mumps to ascertain exposure, travel, and vaccination histories and identify close contacts. Cases were classified as confirmed if the patient had laboratory confirmation of mumps virus or probable if they had clinical symptoms and either a positive serological test or a known epidemiological link to a confirmed case.

FINDINGS

2954 cases of mumps related to the outbreak were identified during the outbreak period: 1665 (56%) were laboratory confirmed, 1676 (57%) were in children aged 5-17 years, and 1692 (57%) were in Marshallese people. Among the 1676 school-aged cases, 1536 (92%) had previously received at least two doses of a vaccine containing the mumps virus. Although 19 cases of orchitis were reported, severe complications were not identified. Unusual occurrences, such as recurrent parotitis and prolonged viral shedding, were observed mostly in Marshallese individuals. Viral samples were characterised as genotype G.

INTERPRETATION

This large-scale outbreak, primarily affecting a marginalised community with intense household crowding, highlights the need for coordinated, interdisciplinary, and non-traditional outbreak responses. This outbreak raises questions about mumps vaccine effectiveness and potential waning immunity.

FUNDING

Council of State and Territorial Epidemiologists and US Centers for Disease Control and Prevention.