The ECDC ELDSNet surveillance scheme on travel-associated Legionnaires’ disease (TALD)  observed an increase in the number of cases associated with travel to Dubai in the last quarter of 2016, compared with previous years (Figure 1). Since 2011, an annual increase of 40% has been reported in the number of TALD cases associated with Dubai; the doubling of cases observed in October and November 2016 (compared with 2014 and 2015) led to an ECDC rapid risk assessment, which was published on 23 December 2016.
As of 17 January 2017, 33 TALD cases with a history of travel to Dubai within 2–10 days of onset of illness and onset since 1 October 2016 have been reported to ECDC from seven EU Member States (Figure 1). Thirty cases associated with commercial accommodation sites were reported through the ELDSNet TALD surveillance scheme. Although private accommodation sites are not part of this surveillance scheme, three cases associated with stays in private accommodation sites in Dubai during this period were identified and reported by the United Kingdom.
Cases were reported by the United Kingdom (16 cases), Sweden (5), the Netherlands (4), France (3), Denmark (2), Germany (2) and Belgium (1). The delay between week of onset and week of reporting to ELDSNet is around two weeks on average, ranging from one to six weeks. Therefore, the number of cases reported in the past six weeks (Figure 1) may be underestimated.
Figure 1. Distribution of TALD cases with history of stay in Dubai within 2–10 days of onset of illness, United Arab Emirates, by week of onset, accommodation site clustering, weeks 37–52/2016
All 33 cases were in Dubai during the incubation period of their Legionnaires’ disease (ELDSNet TALD surveillance definition of 2−10 days prior to illness onset). Figure 2 shows the time period the cases spent in Dubai relative to the onset of their illness. The median time for the illness incubation period is six days, and 60% (20/33) of the reported cases stayed in Dubai for six or more days of the incubation period prior to the onset of illness. Seven cases (21%) were in Dubai during the nine days considered as their probable incubation period. More than 73% (22/30) of cases stayed four or more nights in commercial accommodations in Dubai. The three UK cases who stayed at private accommodation sites had a duration of stay between 11 and 18 days, including 7 to 9 days of their incubation period. Five cases spent time in a further location in the United Arab Emirates (UAE) or another country other than their home country during their incubation period. One of the notified cases was reported as a fatal case.
Figure 2. Distribution of TALD cases with a history of stay in Dubai, United Arab Emirates, within 2–10 days of onset of illness, by time period spent in accommodation sites, 17 September – 31 December 2016 (n= 33 cases)
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All 33 cases were laboratory confirmed. Twenty-five cases were diagnosed with a urinary antigen test (UAT), three with PCR, three cases with both urinary antigen test and PCR, and two by culture, UAT and PCR. Four of the cases with onset of symptoms since 1 October 2016 had their infection further characterised as Legionella pneumophila serogroup 1, sequence base type 616. This type is uncommon in Europe and has been associated with other Legionnaires’ disease cases returning from Dubai in previous years (personal communication, ELDSNet network).
The UAE authorities informed ECDC that there was no observed increase during between October and December 2016 in statutory notifiable pneumonia cases among those seeking healthcare in Dubai.
Public health authorities in the UAE informed ECDC that environmental investigations at the notified hotels were undertaken; all Legionella count results were within acceptable levels for water systems (<1000 cfu/litre) as specified in the water system guidelines for the Dubai municipality . This threshold of acceptability is the same as that indicated in the EWGLI technical guidelines . No information from the UAE authorities has been provided to ECDC concerning whether other environmental investigations were undertaken in Dubai.
ECDC threat assessment for the EU
The threat assessment stated in the rapid risk assessment published on 23 December 2016 has not changed.
- European Centre for Disease Prevention and Control. European Legionnaires’ Disease Surveillance Network (ELDSNet) − Operating procedures. Stockholm: ECDC; 2012. Available from: http://ecdc.europa.eu/en/publications/Publications/1202-TED-ELDSNet-operating-procedures.pdf
- Dubai Municipality, Public Health and Safety Department. June 2010. Guidelines for the control of Legionella in water systems. Dubai: Dubai Municipality, Public Health and Safety Department; 2010.
- European Working Group for Legionella Infections. EWGLI technical guidelines for the investigation, control and prevention of travel associated Legionnaires’ disease. London: EWGLI; 2011. http://ecdc.europa.eu/en/healthtopics/legionnaires_disease/ELDSNet/Documents/EWGLI-Technical-Guidelines.pdf