Category Archives: Water Safety

Research – Heterotrophic Plate Count Can Predict the Presence of Legionella spp. in Cooling Towers



Legionella pneumophila (Lp) colonizes aquatic environments and is a potential pathogen to humans, causing outbreaks of Legionnaire’s disease. It is mainly associated with contaminated cooling towers (CTs). Several regulations, including Spanish legislation (Sl), have introduced the analysis of heterotrophic plate count (HPC) bacteria and Legionella spp. (Lsp) in management plans to prevent and control Legionella outbreaks from CTs. The 2003 Sl for CTs (RD 865/2003) considered that concentrations of HPC bacteria ≤10,000 cfu/mL and of Lsp ≤100 cfu/L are safe; therefore, no action is required, whereas management actions should be implemented above these standards. We have investigated to what extent the proposed standard for HPC bacteria is useful to predict the presence of Lsp in cooling waters. For this, we analyzed Lsp and HPC concentrations, water temperature, and the levels of chlorine in 1376 water samples from 17 CTs. The results showed that in the 1138 water samples negative for Legionella spp. (LN), the HPC geometric mean was significantly lower (83 cfu/mL, p < 0.05) than in the positive Lsp. samples (135 cfu/mL). Of the 238 (17.3%) LP samples, 88.4% (210/238) were associated with values of HPC ≤10,000 cfu/mL and most of them showed HPC concentrations ≤100 (53.7%). In addition, a relatively low percentage of LP (28/238, 11.6%) samples were associated with HPC bacteria concentrations >10,000 cfu/mL, indicating that this standard does not predict the colonization risk for Legionella in the CTs studied. The present study has demonstrated that a threshold concentration ≤100 cfu/mL of HPC bacteria could better predict the higher concentration of Legionella in CTs, which will aid in preventing possible outbreaks.

Research – Surveillance of Vibrio parahaemolyticus pathogens recovered from ready-to-eat foods

This study examined the occurrence of V. parahaemolyticus from ready-to-eat (RTE) food in Delta State, Nigeria. It also characterized antibiotic resistance and virulence gene profile patterns to determine the associated health risk hazard. Food samples total of 380 were collected randomly and assessed for V. parahaemolyticusV. parahaemolyticus isolates were characterized for their virulence and antibiogram potentials using a phenotypic and polymerase chain reaction (PCR) approach. A total of 42 (11.1%) samples were contaminated with V. parahaemolyticus. In 17/42 (40.5%) of the V. parahaemolyticus-positive samples, the densities were < 10 MPN/g. However, 19/42 (45.2%) and 6/42 (14.3%) of the samples had densities of 10 – 102 and > 102 MPN/g, respectively. A total of 67 V. parahaemolyticus isolates were identified using PCR; 54(80.6%) isolates were multidrug resistant. A total of 22 (32.8%), 39 (58.2%), and 67 (100%) of the V. parahaemolyticus harbored the tdhtrh, and tlh toxin genes, respectively. The T3SS1 gene (vcrD1) was detected in 67 (100%) of the isolates. The T3SS2α genes which were vcrD2vopB2, and vopT were detected in 21 (31.3%), 11 (16.4%) and 30 (44.8%) of the isolates respectively. Some of the V. parahaemolytics strains harbored the orf8 gene 20 (29.9%), and a combination of orf8 + tdh genes 12 (17.9%), categorized as pandemic strains. The antibiotic resistance genes detected in this study include blaTEM 33 (49.3), tetM 19 (28.4), cmlA 32(47.8) and sul1 14 (20.9). The concentration levels and prevalence of V. parahaemolyticus in RTE foods indicate contamination of ready-to-eat foods, particularly street foods consumed in the Delta State of Nigeria, threatening public health and consumer safety.

Research – Solar water disinfection effective for E. coli at high, low altitudes


Solar water disinfection (SODIS) may be just as effective at decontamination E. coli-infected water at high altitudes as it is at low altitutdes, according to a press release by Elsevier.

The results of a new study appearing in the Wilderness Medical Society’s official journal Wilderness & Environmental Medicine, published by Elsevier, shows promise this method of disinfection..

Water can be successfully disinfected through several methods: heat, filtration, chemical treatment, and ultraviolet (UV) light. The use of natural sunlight for solar disinfection of contaminated water effectively inactivates many microorganisms, including bacteria, viruses, protozoa, and fungi.

A team of researchers at the University of Colorado Anschutz Medical Campus conducted an experimental study to determine the effect of SODIS on water purification at high altitude (above 2,500 meters) compared to low altitude (below 2,500 meters) among different types of water containers.

“No other published research examining the effectiveness of SODIS at high altitude is available to our knowledge,” said William Mundo, lead investigator of the study. “Adequate access to water, sanitation, and hygiene is a crucial component of human health during emergency situations such as natural disasters and extreme weather events, which are becoming prevalent with climate change.”

A study design previously described in the literature was modified, most notably to evaluate the concentration of E. coli colony-forming units (CFUs) at multiple time points throughout the required six hours of direct sunlight, as recommended by the World Health Organization.

Compared to control containers with no sunlight exposure, the researchers found that all bacteria were inactivated by six hours. At two hours, bacterial inactivation at high altitude was 1.7-fold greater than at lower altitude, however, at the end of six hours, there were no significant differences between high and low altitude samples.

Research – Exploring the Link Between Legionnaires’ Disease and Pneumonia

CDC legionella

Most of us have heard of Legionnaires’ disease and we are all likely to be aware of pneumonia too, but did you know there is a link between the two?

There are many illnesses and conditions that can affect the lungs. Legionnaires’ disease presents as a serious type of pneumonia. This is an inflammation of the lungs. Below, we’ll go into more detail about the link between Legionnaires’ disease and pneumonia. Both can be fatal, particularly among those who are more susceptible to this type of infection than others.

A version of this story exploring the link between Legionnaires’ disease and pneumonia appeared in Legionella Control International’s newsletter. To get it in your inbox, sign up for free at the link above

Research – Catalan Food Safety Agency – Quality criteria for drinking water used in the food industry


On January 12, 2023 , Royal Decree 3/2023  came into force, establishing the technical-sanitary criteria for the quality of drinking water , its control and supply .

This new Royal Decree represents a new, broad and complex regulatory framework to protect human health from any contamination of drinking water. Establishes the technical-sanitary criteria and the quality control of drinking water throughout the supply chain, from catchment water bodies to the user’s tap, with the aim of guaranteeing that drinking water is healthy and clean.

It also specifically establishes the quality criteria for drinking water used in the food industry (CHAPTER VI Water quality in the food company) :

  • It establishes the quality criteria, as well as the parameters and parametric values ​​of the water used for the manufacture, preparation or treatment of food, as well as for washing materials intended for contact with food.
  • The food company will be responsible for the quality of the water from the point of delivery to the connection or in the case of supply in tanks or mobile tanks, of all the phases that it carries out and that, as such, are described in the self-control systems based on in the principles of Hazard Analysis and Critical Control Points (HACCP).
  • The operator of the food company must ensure the quality of the drinking water used, through a sampling plan, different types of analysis and controls, which will be included in their self-control systems based on the HACCP principles. 

This regulation partially transposes Directive (EU) 2020/2184 in Spain  ,  relating to the quality of water intended for human consumption  and repeals Royal Decree 140/2003,  which establishes the sanitary criteria for the quality of drinking water .

Ireland – Boil Water Notice as parasite detected in East Limerick water -Cryptosporidium

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Approximately 470 consumers living close to the Tipperary border have been issued a Boil Water Notice. Traces of cryptosporidium was detected in the Glengar Public Water Supply. A map of the affected area is available to view on the supply and service section of

Following consultation with the (HSE), Uisce Éireann and Tipperary County Council, all consumers affected by this notice are advised to boil their water before drinking it.

supplied by the Glengar Public Water Supply scheme.  Uisce Éireann and Tipperary County Council are issuing this Boil Water Notice with immediate effect.

The notice impacts customers in Glengar, Leugh, Knockanavar, Moher East, Moher West, Shanacloon, Gortaderry, Ballyhane East, Ballyhane West and surrounding areas.

Vulnerable customers who have registered with Uisce Éireann will receive direct communication on this Boil Water Notice and are reminded that the water is safe to consume once boiled and cooled.

Water must be boiled for Drinking;

Research – Correlation of High Seawater Temperature with Vibrio and Shewanella Infections, Denmark, 2010–2018



During 2010–2018 in Denmark, 638 patients had Vibrio infections diagnosed and 521 patients had Shewanella infections diagnosed. Most cases occurred in years with high seawater temperatures. The substantial increase in those infections, with some causing septicemia, calls for clinical awareness and mandatory notification policies.

Vibrio and Shewanella spp. bacteria cause a variety of human infections, including wound infections, ear infections, septicemia, and gastroenteritis (1). Domestically acquired Vibrio and Shewanella infections occur only sporadically in countries in northern Europe because the coastal seawater temperature tends to be too cold to support growth and high bacterial pathogen concentration levels (2,3). However, the warming of low-salinity coastal waters of the Baltic Sea has promoted the growth of Vibrio and Shewanella spp. and consequently increased the risk of disease for humans exposed to such seawater (4). In the unusually warm summer of 1994 in Denmark, several V. vulnificus and S. algae infections were seen among patients who reported bathing in seawater (5,6). Furthermore, during 2014–2018, more than 1,055 cases of vibriosis were reported in northern Europe countries, including Denmark (7).

Considering the annual increase in infections during recent summer seasons in Denmark and the recurring heatwaves across Europe, this emerging public health threat requires more investigation to provide decision-makers with evidence for action. The aim of our nationwide study was to describe the distribution of Vibrio and Shewanella infections in Denmark during 2010–2018 and investigate a possible correlation between infections and sea surface temperature.

Research – Legionella pneumophila Risk from Air–Water Cooling Units Regarding Pipe Material and Type of Water


Legionella A


Legionellosis is a respiratory disease related to environmental health. There have been manifold studies of pipe materials, risk installations and legionellosis without considering the type of transferred water. The objective of this study was to determine the potential development of the causative agent Legionella pneumophila regarding air–water cooling units, legislative compliance, pipe material and type of water. Forty-four hotel units in Andalusia (Spain) were analysed with respect to compliance with Spanish health legislation for the prevention of legionellosis. The chi-square test was used to explain the relationship between material–water and legislative compliance, and a biplot of the first two factors was generated. Multiple correspondence analysis (MCA) was performed on the type of equipment, legislative compliance, pipe material and type of water, and graphs of cases were constructed by adding confidence ellipses by categories of the variables. Pipe material–type of water (p value = 0.29; p < 0.05) and legislative compliance were not associated (p value = 0.15; p < 0.05). Iron, stainless steel, and recycled and well water contributed the most to the biplot. MCA showed a global pattern in which lead, iron and polyethylene were well represented. Confidence ellipses around categories indicated significant differences among categories. Compliance with Spanish health legislation regarding the prevention and control of legionellosis linked to pipe material and type of water was not observed.

USA – FDA investigates cases of Legionnaires disease on cruise ships

Food Safety News

FDA Warning Letters

American Cruise Lines
Guilford, CT

American Cruise Lines is on notice from the Food and Drug Administration (FDA) after an inspection of their American Star and American Heritage vessels. According to the warning letter, the FDA continues to have concerns with the potential exposure of passengers and crew members to Legionella onboard American Cruise Lines’ vessels.

In Jan. 24, 2023, warning letter, the FDA described an April 30 through June 17, 2022, an inspection of American Cruise Lines’ American Star and American Heritage vessels.

The warning letter includes information about failed water tests for a sink in the galley and hand-washing sinks for wait staff. The FDA also found that disinfection was ineffective.

American Star
Presence of Legionella Onboard the Vessel

On April 30, 2022, FDA investigators collected 10 biofilm swabs and 14 bulk one-liter potable water samples from various locations on the vessel. The Maryland Department of Health laboratory recovered Legionella from:

Biofilm Swabs with 60 percent of samples positive:

American Heritage

Presence of Legionella Onboard the Vessel

On June 15, 2022, FDA investigators collected 24 biofilm swabs and 29 bulk one-liter potable water samples from various locations on their vessels. The Maryland Department of Health laboratory recovered Legionella from:

Biofilm Swabs with 8 percent of samples positive:

Research – Outbreak of Shigella sonnei in the EU/EEA and the United Kingdom among travellers returning from Cabo Verde


As of 16 February 2023, 10 EU/EEA countries and the UK reported and the US reported 221 confirmed Shigella sonnei infections and 37 possible cases, all with a link to Cabo Verde.

Information on possible ways of infection or common exposure have not yet been identified but investigations are ongoing in Cabo Verde. Multiple modes of transmission are plausible, and the most likely way is through food, including via infected food handlers. However, person-to-person transmission is also possible.

The S. sonnei strain in the current outbreak indicates predicted resistance to trimethoprim and streptomycin but in some cases, multidrug resistance has also been detected.

Based on the available information, many cases are reported to have stayed in all-inclusive hotels located in the region of Santa Maria on the island of Sal. The most recent cases were reported in Sweden on 19 January 2023, suggesting an ongoing moderate risk of new infections among travellers to Cabo Verde, particularly among those staying in the region of Santa Maria on the Island of Sal.

Shigellosis is a gastrointestinal infection caused by one of four species of Shigella bacteria: Shigella sonnei, S. flexneri, S. boydii and S. dysenteriae. Humans are the primary reservoirs for Shigella.

Shigellosis is caught by oral contact with material contaminated by faeces, either through direct person-to-person contact, via contaminated food or water, or via objects which have been in contact with faeces. The necessary dose for infection is small, which increases transmissibility.

Food-related outbreaks are often caused by infected food handlers, who contaminate ready-to-eat food items like salads. Waterborne infection can occur if drinking or recreational water is contaminated with faeces from an infected person.

Handwashing with soap and water is important, especially after using the toilet and before preparing or eating food. Additional care with food and drinking water when travelling abroad is also important. There is no vaccine currently available to prevent Shigella infection.

People with shigellosis should not attend school, handle food, or provide child or patient care whilst ill. Children under the age of five, food handlers, and healthcare staff should stay at home for 48 hours after their symptoms have ceased.

ECDC encourages public health authorities in the EU/EEA to increase awareness among healthcare professionals on the possibility of Shigella infections among people that recently travelled to Cabo Verde.

Together with WHO/Europe, ECDC is in regular contact with authorities in Cabo Verde to support investigations on the sources of infection and to increase awareness among healthcare professionals in the country.