Legionnaires' disease in Scotland
Surveillance report 2017 to 2022

About this release

This release by Public Health Scotland (PHS) is the first report of Scottish Legionnaires' disease data since the pandemic and covers the years 2017 to 2022. Legionnaires' disease surveillance data is usually published every two years in Scotland.

Legionnaires' disease is a notifiable disease under the Public Health etc. (Scotland) Act 2008. PHS has conducted enhanced surveillance of Legionnaires' disease alongside the Scottish Microbiology Reference Laboratory (SMiRL) since 1994, collecting demographic data, clinical and microbiological information, and risk factors. This allows us to identify and monitor trends, detect outbreaks, identify potential sources of infection and inform measures to reduce the public health risk. Surveillance in Scotland is integrated with that of the rest of the UK.

Main points

• Case numbers and incidence in Scotland were stable from 2017 to 2019, ranging from 6.5 to 6.8 cases per million population annually. Lower case numbers and incidence were observed during the COVID-19 pandemic years in 2020 and 2021, possibly reflecting the travel restrictions in place. Case numbers and incidence increased in 2022, exceeding pre-pandemic levels with no common sources, exposures or links identified.
• Legionnaires' disease cases were observed to peak in Q3 (July to September) of each year from 2017 to 2022. This was driven largely by travel-associated cases, highlighting the peak travel season over summer months. This trend was also observed during quarter three of 2020 and 2021, during which time COVID-19 travel restrictions were reduced.
• Travel-associated Legionnaires' disease accounted for most cases (59.4%) during the period 2017 to 2022, consistent with previous years. During 2020 and 2021, the proportion of travel-associated cases was less than community-acquired cases, reflecting reduced travel due to lockdown restrictions.
• During the period 2017 to 2022, 94.1% of cases were aged 40 years and older; comparable to the age distribution reported for Europe by ECDC in 2021, where 91% of Legionnaires' disease cases were in those aged 45 years and older.
• Between 2017 to 2022, there were nine deaths in Legionnaires' disease cases equating to an average case fatality rate (CFR) of 5% and a range of 0% to 15% in this period. In Europe, CFR for Legionnaires' disease cases was reported to be 9% in 2021.

Further information

The next release of this publication will be August 2024.