Most cases of Legionnaires’ disease are community-acquired, with a slightly lesser percentage contracted abroad, this has not demonstrably changed over the time period. Neither has the fact that the period between July and September typically sees the most cases. Means of diagnosis and that of gathering data and assessing epidemiology have not dramatically changed either. Conversely, the management information available for duty holders to control Legionella has increased with the introduction of the revised Approved Code of Practise (L8) and considerably enhanced guidance through the HSG 274 series and HSG 282.
Our climate is and has changed, however. For those years where the temperature has been particularly high, 2006, 2018 and 2019 being examples, these are the only years where cases of Legionnaires’ disease are over 500 in the reference period. For 2004 and 2011 (another two warm years) however, the reported cases of the disease were the lowest being just over 300 for the former and well below it for the latter. The rest of the results, regardless of temperature are relatively close to the median.
From a rainfall perspective though, while 2004 and 2011 both recorded figures over 1,500mm, the rain tended to fall in “deluge” in parts of the country rather than consistently across it. For 2006 and 2018 rainfall was more consistent and 2019, as most will remember, was wet.
Knowing how Legionella grows and is disseminated, could it be that when the Summer and Autumn months are warm and wet in future there is a likelihood that we will naturally see more cases of Legionnaires’ disease occurring?