Pontiac Fever

Pontiac fever (PF) is a mild form of legionellosis (see this term) manifesting with flu-like symptoms such as nausea, myalgia, fever, cough and headache but without pneumonia.

Epidemiology

The incidence is unknown. Due to the disease's mild and non-specific manifestations it is thought to be underreported. PF is characterised by a high attack rate (number of patients affected / number of people exposed) of up to 95%.

Clinical description

Pontiac fever has a short incubation period ranging from 30-90 hours after infection and affects mainly adults but also children. The disease manifests as an influenza-like syndrome with fever, headache, myalgia and fatigue. In some cases, patients may also experience thoracic pain, dyspnea, diarrhea and vomiting, ocular redness with photophobia and arthralgia. These symptoms usually last 2-7 days and patients recover without treatment.

Etiology

PF is caused by an infection with Legionella pneumophila and Legionella non-pneumophila by inhalation of aerosols from contaminated water, most frequently from showers, whirlpools, spas and hot tubs. The bacteria are found in wet soil and water. It is currently unknown why infection with Legionella evolves into LD or PF in any given case, but as PF is usually observed in immunocompetent patients, immune system status could play a role.

Diagnostic methods

Laboratory diagnosis is rarely performed and is usually done retrospectively by detecting seroconversion or high titers of antibody to Legionella in serum samples. The diagnosis can also be made by detection of the L. pneumophila antigen in urine samples.

Differential diagnosis

Influenza closely resembles PF and must therefore be excluded.

Management and treatment

No treatment is needed for PF and recovery without treatment is the rule.

Prognosis

There is no fatality associated with PF.