LEGIONELLA AWARENESS SEMINAR for the NORTH WEST WALES HEALTH AND SAFETY GROUP by Ken Ashley formerly HM Specialist Inspector HSE Dangerous Pathogens Section now Independent Consultant

SESSION ONE LEGIONNAIRES’ DISEASE AND LEGIONELLA BACTERIA

Legionnaires’ disease First recognised July 1976 Philadelphia American Legionnaires’ convention 182 cases of pneumonia 29 died

Legionella : Hazard or risk? The hazard : is the presence of Legionella bacteria in your water system. The risk: is: Legionella bacteria growing to a sufficient level to cause Legionnaires’ disease in the population exposed

Legionnaires' disease in Residents of England & Wales by Category of Exposure 1980 to 2004

What is the real number of cases? Under-reporting Estimate 1. –Countries with best surveillance report 20 cases / 10 6 p.a. –This suggests in England & Wales a total of 52 x 20 = 1040 cases p.a. –Estimate 2 –2000/ ,565 cases of pneumonia in England in 1 year –Agent identified in <5% –Estimates of true incidence of LD based on intensive studies of patients in hospital with pneumonia caught in the community suggest 2% – 3% of all community acquired pneumonias are legionnaires’ disease –This suggests in England & Wales there are about 5500 cases p.a.

Legionellosis - an infection caused by Legionella Severest - legionnaires’ disease – Low attack rate – infects less than 5% of those exposed –atypical pneumonia: –symptoms: cough - usually dry, 75%; fevers 70%; confusion, 45%; new sputum, 45%; bad headache, 32%; diarrhoea & vomiting ~30% –up to 40% die (European average 13%) –Incubation (time from exposure to first symptoms) : 2 – 10 days –but sometimes 16 or even up to 21 days (may be longer in the immunocompromised) Mild - Pontiac / Lochgoilhead fever –high attack rate: affects over 95% of exposed –influenza like illness: no deaths –incubation: 12 – 48 hours Asymptomatic (healthy without symptoms) – – (serological evidence) of exposure to infection

Mode of infection Inhalation of organisms suspended in air (aerosol - not a spray) Rarely by aspiration, maybe significant for patients in the dental chair? No evidence of person to person –Factors NB for infection include: »Bacterial burden (infectious dose unknown) »Effectiveness of dissemination »Virulence of organism »Patient susceptibility

Growth requirements of legionella bacteria Grows well between 29 o C- 40 o C with an optimum of 35 o C Will grow between 20°C and 45°C Below 20°C legionella survives but does not grow Above 50°C legionella is killed Food e g sludge in a calorifier Presence of cysteine(an amino acid) and iron Iron increase growth 10,000 to 100,000 fold

Susceptibility to physical and chemical agents Heat eg hot water above 50°C and particularly above 60°C as used in hot water storage Biocides used in hot and cold water services where temperatures cannot be achieved such as chlorine dioxide or silver ions

Cultural characteristics Do not grow on ordinary nutrient media Up to 14 days to grow legionella Reminder-monitoring is a snapshot Reminder-monitoring is not control Most clinically important bacteria grow within 18 to 24 hours Reminder-dip slides do not detect legionella bacteria

Identification Culture-for both patients and plant Urine antigen(patients) Antibody(patients) Gene probe(both but will detect dead organisms in plant as well as live)

Habitat Wide-spread in natural water sources –Rivers and lakes - therefore in the water supply –Mud and soil –Then will enter into many man made systems eg hot and cold water systems, cooling towers etc as less sensitve to chlorine than most waterborne bacteria. –Therefore you cannot avoid it entering your practice

Habitat Biofilm Other organisms are needed, particularly ameobae in a water system that ‘graze’ on the water/suface interface eg the inner surface of a pipe When legionella bacteria burst from an amoeba there are about 10,000 released into the water

Pathogenicity Mainly, L. pneumophila serogroup 1 and 6 L. micdadei, L. dumoffi You need to know the name of the organism in bullet point one as this is the one that causes 90% of cases/outbreaks

Statistics summary 600 or so cases per year(much higher in 2002 because of Barrow) MOST cases are caused by H&CW 50% possibly travel associated if you include returning to an infected water system at home Usually 10-12% mortality(in hospitals up to 40%) Males more likely to be affected (3:1)

Conditions required for proliferation Water containing legionella (inevitable) Temperature between 20°C and 45°C, noting that the maximum growth is between 30°C and 40°C Food source eg organic debris such as leaves or animal access to cold water tanks Stagnation eg blind ends or surfaces beneath scale and rust as often found in old domestic (some of your practices) hot and cold water systems

Factors promoting infection Presence of airborne droplets containing viable legionella Chain of events –Presence of legionella –Conditions suitable for multiplication/proliferation to high numbers –Means of creating breathable droplets –Exposure of susceptible person

Who is most susceptible? Men more than women ( ≈ 3 : 1) Aged > 50 years Smokers Heavy drinkers Diabetics Chronically ill Immuno-suppressed –transplant patients –Steroid treatment

BARROW IN FURNESS July/August 2002 Approximately 175 infected and 7 deaths Stafford in 1985 was 100+ cases and 28 deaths Associated with a cooling tower used to reject heat from an air conditioning system

Summary Moisture/water needed Temperature between 20 o C and 45 0 C Nutrients from sediment, sludge, scale, compatible organisms and materials used in construction Presence of biofilm, stagnation and conditions to promote proliferation Breathable droplets