No 41 - 2011

Legionella-pneumonia 2010

Legionella bacteria are found in water and can reproduce at temperatures of 25-50º C. Legionella pneumonia (LP) is acquired through inhalation of an aerosol containing the bacteria, e.g. from the water supply of homes, hotels, sports facilities or hospitals. Other infection sources include cooling towers, spa baths and wateratomizing facilities. LP is notifiable on Form 1515, and Department of Epidemiology sends out reminders concerning laboratory-confirmed cases.

Notified cases 2010

A total of 121 notified cases of LP were detected with onset in 2010. Among these, 94 cases were laboratory-confirmed as described in EPI-NEWS 40/09 (pdf). The median age was 61 years (range 23-89) and 87 (72%) were males. For 65 patients, a minimum of one predisposing factor was reported, six had no predisposing factors and in 50 cases information on predisposition was missing. A total of 90 cases were infected in Denmark. Infection categories are presented in Table 1, and geographical distribution in Table 2.

Occupational cases

A total of 13 persons are believed to have been infected at work, including nine in Denmark; only one of these was culture-positive. At one place of employment, Legionella was detected in water samples. Four cases are believed to have been infected during stationing abroad. Two of these cases were culture-confirmed, both concerned presumed infection during a work-related stay in Eastern Europe.

Cases acquired in health care sector

Three died in connection with their legionella infection. In two of the cases, water sample analysis supported the suspicion of infection route. In one case, no culture of patient material was available, only positive culture of a water sample. Two cases were from the same institution, but had different serotypes.

Other places of infection

In a total of 68 cases with presumed community-acquired infection, 23 cases were culture-confirmed. In nine cases, samples from the water supply of the patient’s home were known to have been analysed. In three of these, the typing result from the water sample isolate and patient samples matched, and the source of infection could thus be confirmed.

Travel-associated cases

A total of 31 cases were presumably infected abroad and three while on vacation in Denmark, Table 3. Among these, 27 were reported to the European Centre for Disease Prevention and Control (ECDC). In nine (28%) of the cases, predisposing factors were either unknown or not stated. A total of 14 cases were cultureverified. In two of these, typing results from the water supply of the hotels where patients had stayed confirmed the source of infection.

Laboratory-confirmed cases

2011 saw a total of 126 laboratory-confirmed LP cases, including 22 cases which were only confirmed by PCR (including five non-pneumophila). Legionella was isolated by culture from 53 patients. Five confirmed cases were notified. The distribution of legionella isolates was as follows: 34 L. pneumophila serogroup (sg) 1 (22 Pontiac and 12 non-Pontiac), one sg 4, two sg 6, one L. bozemanae (previously L. bozemanii). The distribution on serogroups was appr. equivalent to previous years.

Commentary

Cases may be considered presumably acquired in the health care sector or travel-associated if the patient has been admitted or travelling in 2-10 days before symptom onset. Cases acquired in the health care sector are handled by local hygiene organisations, often in corporation with the SSI Central Infectious Hygiene Unit. Every year sees clusters among persons who have stayed at the same hotel. SSI reports travel-associated cases to ECDC to improve prevention in the country in question. Information on symptom onset, hotel stay periods, and any relevant details, including room number and exposure to sources to water aerosols, are therefore very valuable in LP notification.

International outbreak in Italian vacation area, August 2011

In cooperation with ECDC, the Italian health authorities initiated investigations and instituted preventive measures due to an outbreak of LP among tourists in the Lazise area by the Gardasee. A total of 17 cases of infection were detected, including one Danish case. No new cases have been observed after 23 August, and the outbreak is therefore considered ended. However, attention should be paid to possible cases of LP in patients who have previously visited the area. Such cases are mandatorily notifiable immediately by using Form 1515.

(C. Kjelsø, S. Ethelberg, Department of Epidemiology, S. Uldum, C. Wiid Svarrer, DBMP)

Vaccination of pilgrims travelling to Mecca

To obtain a visa for Saudi Arabia, anyone above the age of two years shall have received the tetravalent vaccine against meningococcal disease of serogroups A+C+W135+Y (Menveo®). All travellers over the age of two years, including those who have been vaccinated against groups A and C within the past three years, must be vaccinated with one 0.5 ml dose no later than 10 days before entry to the country. Children between three months and two years shall be vaccinated with a vaccine providing protection against group A meningococci. The National Danish Board of Health has assessed that children aged 3 months to 1 year may receive primary vaccination in the form of two 0.5 ml doses of Menveo® given at an interval of at least one month. Children aged one year or older should be given a single 0.5 ml dose, EPI-NEWS 37/10. 

(Department of Epidemiology)

Increased number of Mycoplasma pneumoniae cases

The number of samples tested positive for Mycoplasma pneumoniae by PCR has increased considerably as from August 2011. At Statens Serum Institut, Week 39 of 2011 alone produced 18 positive samples from the 110 tests performed (16%). The same proportion of positive tests was observed in the same period last year (but then a considerably higher number of tests were made), EPI-NEWS 40/10 and 41/10.

Last year, Denmark saw a regular epidemic which peaked in the beginning of December 2010, EPI-NEWS 48/10. It is not unusual for Mycoplasma pneumoniae epidemics to continue for several seasons, even though few cases are seen in the spring and summer. The present increase in the number of Mycoplasma pneumoniae cases may escalate into an actual epidemic in the course of a month or so, but the current increase may also be a minor autumn peak which will typically recede over a number of weeks. Statens Serum Institut follows developments closely.

12 October 2011