Legionella is a species of Gram negative bacterium that is associated with a group of human infections known as Legionellosis.  Legionellosis is a group of infections including: Legionaires’ disease (a form of pneumonia, with a typical mortality rate of 15%); Pontiac Fever (a much less serious, flu like illness) and Lochgoilhead Fever (a non-fatal disease associated with L. Micdadei).  Infection occurs by breathing in water droplets (aerosols) containing the bacterium, and there are no recorded cases of person to person infection.  It is generally accepted that it is not normal to become infected by drinking contaminated water, although a theoretical risk may exist via aspiration of water. 

Although only identified in 1976 (named after an outbreak of the bacteria at a convention of  US ex-servicemen), the bacteria is now known to have been around for much longer, and occurs naturally in soil and surface waters.  There are at least 48 strains of Legionella and 70 individual serogroups, however by far the most common cause of Legionnaires’ disease is Legionella pneumophila serogroup 1 (Lp sg1).

The bacteria prefer to live in biofilm on the inside of pipes and storage tanks where they are protected from biocides added to destroy them.  In many cases the bacteria actually live inside host amoeba and protozoa.  The bacteria are also reasonably temperature resistant and can survive both freezing and temperatures of 50 ºC, whilst growing fastest between 25-40 ºC with the capability to double in numbers every 90 minutes (under ideal conditions). 

Because of the need to inhale the bacteria, infection is generally associated with water systems where the water is warm (and thus supporting growth) and has the capability of generating an aerosol.  Some of the most common ‘culprits’ for infection are whirlpool spas, industrial cooling towers, air conditioning system, showerheads and food misters.  However there are also risks associated with dental equipment, recreational fountains, fire sprinkler systems, and car washes. 

Water treatment specialists can use the hydrosense Legionella Field Test (or the equivalent Nalco FastPath™ test) as part of their monitoring program, to ensure the fastest possible response to any potential colonization of your water system, thereby helping prevent outbreaks of Legionellosis.

Outbreaks of Legionellosis are  frequently reported across the developed world, and increasingly regulations and guidelines are being introduced to help reduce the risks of infection.  Infections are more common in men, the over 50’s, smokers and those with other respiratory problems as well as people with chronic conditions that debilitate their immune system.  For this reason hospitals and homes for the elderly are particularly vulnerable to outbreaks. 

Different versions of the hydrosense Legionella Field Test (and Nalco FastPath™ test) have been developed to detect Legionella pneumophila serogroup 1 at different concentrations, in line with local regulations.

One of the major problems with managing Legionella has been the time associated with obtaining test results.  Traditional approaches to Legionella detection typically take around 14 days to produce confirmed results.  Using our portable test kit it is possible to obtain test results in less than half an hour!  Without the significant capital cost of other emerging techniques such a PCR.

More information about Legionella, Legionellosis and its prevention can be found here: (hydrosense provides these links for your convenience but cannot be responsible for their content)