A sixth Norwegian has died from an outbreak of Legionnaire’s disease but the rare illness seems to have stopped spreading, department director Preben Aavitsland at the Norwegian Institute of Public Health said on Tuesday.

Another 41 people in south Norway were infected with the bacteria this month. The latest victim died on May 19, but it was not proven until now that the man had died of Legionnaire’s disease, along with five other people in May.

“We believe the outbreak is over,” said Aavitsland.

He said the source of the bug had not yet been identified, but he hoped it would be found next week when results from tests of air-conditioning systems were analysed.

The bacteria, spread by water droplets, are sometimes found in air-conditioning and other water-cooling systems. The disease was first described in 1976 after 34 people died after attending a convention of the American Legion.

Definition
Legionnaire’s disease is an acute respiratory infection caused by the bacterium Legionella pneumophila, which can cause a broad spectrum of disease from mild cough and fever to a serious pneumonia.

Causes, incidence, and risk factors
The bacteria that cause Legionnaire’s disease have been found in water delivery systems and can survive in the warm, moist, air conditioning systems of large buildings including hospitals. The infection is transmitted through the respiratory system. Person-to-person spread has not been proved.

From the onset of symptoms, the condition typically worsens during the first 4 to 6 days, with improvement starting in another 4 to 5 days. Most infection occurs in middle-aged or older people, although it has been reported in children. Typically, the disease is less severe in children.

Risk factors include cigarette smoking; underlying diseases such as renal failure, cancer, diabetes, or chronic obstructive pulmonary disease; people with suppressed immune systems from chemotherapy, steroid medications, or diseases such as cancer and leukemia; alcoholism; being middle-aged or elderly, and in people on a ventilator for extended periods.

The outbreak in two southeast Norwegian towns was the most serious in Norway after a 2001 infection that killed seven people.

Symptoms of the disease include aches, tiredness, headache, dry cough and fever and it is particularly dangerous for elderly and weak people. It can be treated with antibiotics.

Treatment
The goal of treatment is to eliminate the infection with antibiotics. Treatment is started as soon as Legionnaire’s disease is suspected, without waiting for confirmation by culture results.

The antibiotic commonly used is quinolone (ciprofloxacin, levofloxacin, moxifloxacin, or gatifloxacin) or a macrolide (azithromycin, clarithromycin, or erythromycin).

Supportive treatment includes hospitalization for fluid and electrolyte replacement and oxygen administration by mask or by mechanical ventilation, if the respiratory system becomes severely compromised by the infection.