A positive case of Legionella was confirmed at the San Martín Hospital in our city (see: https://www.eldia.com/nota/2023-3-15-10-50-0-la-provincia-en-guardia-por-un-caso-confirmado-de-legionella-en-la-plata–la-ciudad). It is for this reason that the Province activated the alarms for fear of an outbreak like the one that occurred last year that originated in Tucumán and caused several deaths.
As this newspaper reported, this is a 49-year-old patient from the San Martín Hospital who is admitted to intensive care but was referred from the Bone Marrow Transplant Unit. He arrived with the diagnosis of Multiple Myeloma and had an intervention (autologous bone marrow transplant) scheduled on February 24. After the positive results, the authorities are now analyzing how the infection occurred, especially since it was reported that the patient had been hospitalized in mid-February in another ward of the same hospital.
According to information provided by the World Health Organization, legionellosis presents important variations in terms of its severity, since it includes from mild conditions that occur with fever to some forms of potentially fatal pneumonia. The cause of the disease is exposure to Legionella species present in contaminated water and potting soil mixes.
Often, cases of the disease are classified according to the type of exposure, ie: community-acquired, nosocomial, or during travel.
Worldwide, the waterborne species L. pneumophila is the most common cause of infection and even outbreaks. L. pneumophila and related species are often found in lakes, rivers, streams, hot springs, and other water systems. Other species, including L. longbeachae, can be found in potting soil mixes.
The bacterium L. pneumophila was first described in 1977 as the cause of a 1976 outbreak of severe pneumonia at a US convention center. Since then, it has caused outbreaks as a result of poorly maintained artificial water systems.
Although the infective dose is unknown, it can be presumed that it is low for people vulnerable to the bacteria, since cases have been reported after very short exposure times and distances of up to 3 km or more from the source of infection. The probability of contracting the disease depends on the concentration of legionella in the water source, the production and dispersion of aerosols, factors specific to the person, such as age or conditions, and the virulence of the strain of legionella. Legionella in question. Most infections do not cause symptoms.
What causes legionellosis and how is it transmitted?
The pathogens that cause legionellosis are legionella present in water or potting soil mixes. The species that most commonly causes the disease is L. pneumophila, which can be found in natural freshwater bodies around the world. However, artificial aquatic systems are much more dangerous, since they are favorable places for the growth and spread of legionella.
Legionellae live and grow in water at temperatures between 20°C and 50°C (optimum temperature: 35°C) and can survive and thrive parasitizing free protozoa or within biofilms that form in water systems. . In addition, they can infect human cells through a mechanism similar to that used to infect protozoa.
While the most frequent form of transmission of legionella is the inhalation of aerosols with contaminated water. This transmission has been observed in aerosols generated in cooling towers for air conditioning, hot and cold water systems, humidifiers, and hydromassage facilities. The infection can also be contracted by inhalation of contaminated water or ice, especially by vulnerable hospitalized patients, or by exposure of the newborn during water births. To date, there are no known cases of direct transmission between people.
Legionellosis is believed to be present in all parts of the world. The known incidence of this disease varies considerably depending on the level of surveillance and reporting. However, the actual incidence rate is unknown because many countries lack adequate diagnostic tools to detect the infection or because their surveillance systems are inadequate. In Europe, Australia and the United States, 10 to 15 cases per million inhabitants are detected each year.
Between 75% and 80% of reported cases are people over 50 years of age, and between 60% and 70% are men. Other risk factors for contracting community-acquired or travel-associated legionellosis include smoking, excessive alcohol consumption, lung disease, immunosuppression, and chronic respiratory or renal disease.
Risk factors for contracting nosocomial pneumonia are recent surgery, tracheal intubation, mechanical ventilation, aspiration, the presence of nasogastric tubes, and the use of respiratory physiotherapy equipment. The most exposed hosts are immunocompromised patients, for example, transplant recipients and cancer patients, as well as people undergoing corticosteroid treatment.
Delay in diagnosis and administration of adequate antibiotic treatment, advanced age, and the presence of concomitant diseases are prognostic factors for death from legionellosis.
Symptoms
The term “legionellosis” is generic and encompasses both pulmonary and non-pulmonary forms of Legionella infection. The nonpulmonary form (or Pontiac fever) is an acute, self-limiting illness that presents with flu-like symptoms and usually subsides within 2 to 5 days. Its incubation period ranges from a few hours to a maximum of 48 hours. The main symptoms are fever, chills, headache, malaise, and muscle pain. There are no known cases of death by this form.
The pulmonary form, which is what is properly called legionellosis, has an incubation period of 2 to 10 days, although periods of up to 16 days have been recorded in some outbreaks. Initial symptoms are fever, loss of appetite, headache, malaise, and lethargy, although some patients also report muscle pain, diarrhea, and confusion. An initial mild cough is also usually seen, although up to 50% of patients may present with phlegm. In about a third of the patients, the sputum is accompanied by blood. The severity of the disease ranges from a mild cough to rapidly fatal pneumonia; This occurs due to progressive pneumonia, which is accompanied by respiratory failure and/or shock and multi-organ failure.
If left untreated, legionellosis usually gets worse in the first week. As with other risk factors for severe pneumonia, the most common complications of legionellosis are respiratory failure, shock, and acute and multiorgan renal failure. The cure, which always requires antibiotic treatment, is usually complete, although it can last for several weeks or months. On rare occasions, severe progressive pneumonia or the administration of ineffective treatment to treat it can lead to cerebral sequelae.
The mortality rate from legionellosis depends on: the severity of the disease, the adequacy of the initial antimicrobial treatment, the place where the infection was acquired, and various factors related to the host (for example, the disease is usually more severe in immunocompromised patients). ). In immunosuppressed people who are not treated, the mortality rate can reach proportions of 40% to 80%, although it can be reduced to 5%-30% if the cases are attended to well and depending on the severity of the disease. clinical signs and symptoms. Overall, the mortality rate ranges from 5% to 10%.
It should be noted that there are currently no vaccines against legionellosis. The non-pulmonary form of the infection remits spontaneously and does not require medical intervention, not even antibiotics, while legionellosis always requires antibiotic treatment once it has been diagnosed.
To avoid the public health burden of legionellosis, authorities responsible for the safety of buildings or water supply systems should implement specific water sanitation plans for each building or system, which should include the introduction and periodic supervision of control measures for identified risks, including the presence of Legionella. Although it is not always possible to eradicate the source of infection, the risks can be substantially reduced.
The prevention of legionellosis consists of applying control measures that minimize the proliferation of legionella and the diffusion of aerosols, including the good maintenance of the equipment, in particular through its systematic cleaning and disinfection, and the application of other physical measures (thermal) or chemical (biocide) to limit bacterial proliferation as much as possible. These are some of the recommended measures:
– periodically maintain, clean and disinfect the cooling towers, frequently or systematically using biocidal agents;
– install mist separators to reduce the diffusion of aerosols from cooling towers;
– maintain a suitable concentration of biocides (for example, chlorine) in the hydromassage installations and completely empty and clean the entire system at least once a week;
– keep hot and cold water systems clean and keep hot water above 50°C (meaning it must leave the heating unit at 60°C, minimum) and cold water below 25° C or, better still, 20 °C, or treat the facilities with a suitable biocide to limit bacterial growth, especially in hospitals, health establishments and nursing homes;
– reduce stagnant water by opening the taps in buildings that are not in use weekly.
The application of this type of measures will contribute considerably to reducing the risk of Legionella contamination and preventing the appearance of both sporadic cases and outbreaks. When caring for vulnerable hospitalized patients, it may be necessary to apply extra precautions with water and ice, especially to avoid the risk of aspiration (for example, very vulnerable patients should not use ice machines, because they can be a source of legionella).
Control and prevention measures must be accompanied by due surveillance by general practitioners and community health services, with a view to facilitating case detection.
