No 41 - 2010

Legionella pneumonia 2009
Mycoplasma pneumoniae 

Legionella pneumonia 2009

2009 saw a total of 116 notified cases of legionella pneumonia (LP) with onset in 2009.
Among these, 100 cases were verified as described in EPI-NEWS 40/09 (pdf).

The median age was 67 years (range 21-93), and 73 (63 %) were males. For 60 patients, a minimum of one predisposing factor/condition was reported, 11 had no predisposing factors, and in 45 cases information on predisposition was missing.

The distribution by infection categories is shown in Table 1
Table 2 shows the distribution by area of verified cases acquired in Denmark.

Travel-associated cases

A total of 37 cases were travel-associated, Table 3.

Eight of the patients had stayed in hotels with other reports of infection, and one patient formed part of an outbreak occurring during the World Handball Championship in Croatia, EPI-NEWS 9/09 (pdf).

In three culture-verified cases, water samples collected where the infected persons had stayed were tested.
In water samples from a Danish Bed and Breakfast, a DNA type identical to that detected in the patient was found.
In water samples from two foreign hotels, the DNA type detected in the patients could not be matched to that of the hotels.

Nosocomial cases

A total of five presumed or confirmed cases of nosocomial infection were notified; all patients suffered from severe underlying diseases. Statens Serum Institut only knows of one case in which water samples were tested, but as this case was not culture-verified, the source of infection could not be detected.

Other places of infection

In five culture-verified cases, infection via the water supply was confirmed by comparing patient and water samples.

In the spring of 2009, LP was detected in four persons who had visited an indoor swimming pool in the Capital Region.
Water samples from the showers proved to be heavily colonized by L. pneumophila.

The pool was closed and the showers underwent renovation. A plumber who disassembled the infected installation was infected with LP.

Subsequent DNA typing of isolates from patients and water showed that two of the patients (including the plumber) and the water isolates had the same DNA type, while the isolate from one patient had another DNA type.

One patient (not culture-verified) had travelled in Spain during the incubation period and may have been infected there.

Laboratory-diagnosed cases

Statens Serum Institut knows of 115 laboratory-confirmed LP cases (verified plus PCR) in 2009, including 105 verified and ten cases which were only confirmed by PCR (including two non-pneumophila). Five verified cases have not been notified.

L. pneumophila was isolated by culture from a total of 65 patients - the highest number ever recorded.
The distribution of legionella isolates was as follows: 42 L. pneumophila serogroup (sg) 1 (31 Pontiac and 11 non-Pontiac), 12 sg 3, three sg 5, four sg 6, and four sg 10.

The distribution is roughly in line with that observed in recent years; however, this year only L. pneumophila species were detected.


In comparison with other countries, Denmark enjoys a very high proportion (> 50 %) of culture-verified cases.
This is owed to the considerable efforts made by several microbiological departments.

The pool outbreak demonstrates that mixing tanks where hot and cold water is mixed to achieve a temperature of approx. 37°C entails a considerable risk of legionella multiplication.
Furthermore, it is essential that protective respirators (FFP3 masks) be used when working with water installations with a high level of legionella bacteria.
(S. Uldum, DBMP, G. St-Martin, K. Mølbak, Dept. of Epidemiology)

Mycoplasma pneumoniae

In recent weeks, Statens Serum Institut has detected an increasing number of specimens with Mycoplasma (M.) pneumoniae by PCR, primarily from the Capital Region and Zealand, EPI-NEWS 40/10.
In Region South Denmark, a similar increase in the number of positive specimens has been observed.

M. pneumoniae infections occur most frequently in the autumn and the beginning of winter. In Denmark, nation-wide epidemics occur every 4-6 years, most recently in 2004/2005, EPI-NEWS 42-43/04EPI-NEWS 51/04 and EPI-NEWS 10/05, page 2 (all pdf).

Anyone can become infected, but the infection occurs most frequently among children above the age of three years.

Mycoplasma infection presents as fever, flu-like symptoms and cough. Most cases are mild and do not lead to medical consultation. Pneumonia is seen in no more than 10 % of the infected.

M. pneumoniae can be detected early by PCR on airway secretions or throat swabs. Antibodies cannot be detected until 1-2 weeks after symptom onset. To ensure the correct diagnosis by detection of an in-crease of the antibody level, a minimum of two blood samples should be taken at a one-week interval or more.

If the diagnosis is confirmed using laboratory methods, treatment should be initiated provided the patient presents with symptoms.
First-line treatment is recent macrolides, alternatively tetracycline may be used (in adults).
For more detailed information, please see
(S. Uldum, J.S. Jensen, DBMP, S.S. Nielsen, Dept. of Microbiology and Diagnostics , J.N. Rasmussen, Dept. of Epidemiology) 

Individually notifiable diseases and selected laboratory diagnosed infections (pdf) 

13 October 2010