Legionnaire disease raises its head again

Previously associated with tourists staying in hotels with ill kept ACs and hot tubs, Legionnaire disease is becoming increasingly common among the resident population.

Official statistics show that last year Malta recorded 13 cases of the potentially lethal water-borne disease amidst a spike in cases across Europe.

This represents the third highest ever number of annual cases in Malta of the bacterial infection associated with neglected air-conditioning and plumbing systems.

According to the Infectious Disease Prevention and Control Unit (IDCU)’s annual report, nine cases out of the 13 recorded in 2023 involved Maltese residents.

The highest number of cases of Legionnaire Disease in Malta was reported in 2004 and in 2020.

But while 15 out of the 16 cases recorded in 2004 involved tourists, 13 out of the 16 cases recorded in 2020 involved Maltese residents.

A total of 230 cases of this disease have been diagnosed since 1989, of which 101 were recorded since 2013.  A total of 17 deaths have been recorded, six of which in the last decade.

European spike

While the increase in numbers reflects the increase in the local population, it also coincides with a spike in cases across the European continent. In 2021 the EU/EEA witnessed the highest annual notification rate of Legionnaires’ disease to date, with 2.4 cases per 100,000 population.   

Significantly Malta had experienced a record number of cases in the previous year during the first phase of the pandemic.

Factors behind this continental increase according to the European Centre for Disease Control (ECDC) included the lifting of travel restrictions after the first phase of the pandemic, an ageing population; climate change and the design, infrastructure, and maintenance of water systems used in buildings.

Disease now more common among Maltese residents

One notable change is that while in the past the disease was mostly associated with tourists visiting Malta, most cases are now being reported among the resident population.

In the 23 years between 1989 and 2012 Malta recorded only 58 local cases of Legionellosis while 71 cases were associated with travel.

In the record year 2004, 15 of the 16 recorded cases involved tourists.

But in the 11 years between 2013 and 2023 Malta recorded 71 cases among Maltese residents and only 30 cases among non-residents. Moreover, in the record year of 2020, 13 of the 16 cases involved Maltese residents. In 2022 only one case involving a nonresident was recorded while eight cases involved Maltese residents.

In fact, of the 13 cases diagnosed last year 10 were Maltese residents and three were foreigners. Two of the cases involved foreigners who had contracted the disease in Malta before leaving.

The IDCU report does not clearly indicate the source of the infection but indicates that the disease was contracted in both “households” and from “other establishments.” It also adds that “all establishments were investigated, and corrective action was taken if necessary”.

The report does not indicate how many cases were contracted in hotels or from the workplace.

Since 1989 at least 17 people have died after contracting the legionella microbe, six of which in the past decade.  This means that over 7% of those diagnosed with the disease died. But the figure could be higher as the number of deaths resulting from infectious diseasesis not provided in the annual tables issued by the IDCU in 2020, 2021 and 2023.

What is Legionnaire’s disease?

Legionnaire’s is a type of severe pneumonia caused by bacteria, with an overall fatality rate of about 10% which increases among smokers and those with underlying diseases.

It is usually contracted by inhaling water droplets that contains the bacteria from hot tubs, showers or A/C units, but not person to person.

The Legionellae microbe can also grow and multiply inside rarely used plumbing systems. This is because the microbe thrives on biofilm, the coating on the inside of plumbing systems which forms when there is no or poor circulation of water within.

Symptoms of Legionnaire’s disease include fever, chills, a cough and sometimes muscle aches and headaches.

The disease is treated by antibiotics, which are effective when the disease is detected early. The disease owes its name to the victims of the first recorded outbreak of the disease in 1976 at the Bellevue Stratford Hotel in Philadelphia, Pennsylvania, where members of the American Legion, a United States military veterans association, had gathered for the American Bicentennial. Within two days of the event’s start, veterans began falling ill with a then unidentified pneumonia. As many as 221 people were given medical treatment and 34 deaths occurred.

How to prevent Legionellosis

Household plumbing systems are at low risk of carrying the Legionella bacteria unless the plumbing system is unused for a long period of time. Thus, it would be wise to close water systems if you are planning to stay away from your home for a long period of time or if you have part of the system which is not used. On returning, the water should be allowed to run for about five minutes so that any stagnant water which would have been left in the system will be flushed down. Leaving the windows open during such procedures would result in a better dispersion of aerosols generated.

Households are also advised to regularly check water tanks and insulate them to prevent the temperature of the water from warming up. They are also advised not to buy water from bowsers not certified by the Health Department.

Residents in hotel establishments are at a greater risk of exposure. In fact, hotel owners are legally obliged to register the cooling towers and evaporative condensers and to disinfect them regularly and keep them in good condition as stipulated by law.

By law the Health Authority can close establishments where a confirmed case of Legionellosis is recorded. The regulations came in place in 2006 following a spike in the number of cases recorded two years earlier.