LEGIONELLA CÁCERES OUTBREAK | Why does the number of infected people continue to increase?

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Legionella is a disease caused by bacteria Legionella pneumophila

Health authorities are concerned due to the increase in cases in recent years in Cáceres

It has not been a quiet summer in Cáceres. For the second consecutive year, a legionella outbreak has unleashed alarm among its neighbors. Since last August, one person has died as a result of the infection (five people died last year) and more than a dozen have tested positive in legionellosis.

Although the local administration announced that eight fountains located in the city had been closed due to the appearance of legionella in them, and today they are still closed to the public, there is still no trace of the origin of this bacterium. Although there are treatments, there is currently no vaccine against this serious disease.

And, as the Dr. Julio Garcíaspokesperson for the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC), is a really “worrying” bacteria because, above all, affects “people over 50 years of age who either have previous illnesses or are immunosuppressed (with the low defenses)”.

Microscopic image of legionella bacteria | Photographer: Janice Haney Carr

In fact, all confirmed cases of legionella in the city of Cáceres are over 50 years old. This same Thursday, the Extremadura Health Service (SES) confirmed a new contagion. This is a 76-year-old man who is admitted to the San Pedro de Alcántara Hospital. With this, there are already 12 cases registered in the capital of Cáceres so far this summer.

Where is legionella bacteria found?

  • “They are in the natural world and have been found in rainwater, lakes and rivers. The problem arises when systems that use water to function are contaminated.”

Hot water systems, such as spas and showers, as well as nebulizers and sources ornamental plants are the main sources of infection, although outbreaks have also occurred in closed establishments such as hospitals or hotels.

The illness has a seasonal presentationso it is common for cases to occur more frequently “at the end of summer and in autumn.”

Why is Cáceres one of the cities most affected by this bacteria?

Pending the results from the Extremaduran health authorities, Dr. García explains that all administrations “are obliged to carry out inspections to prevent its proliferation in public spaces (Royal Decree 865/2003, of July 4)”.

  • The main prevention measure for cases of legionella, for example, in a fountain located in a public park, is to avoid water stagnations, since it alters the chemical and microbiological quality of the water. And in case an outbreak of legionellosis has been detected, a thorough cleaning must be carried out.

The most common treatment, the specialist emphasizes, is “thermal shocks, increasing the temperature of the water distribution conduits.” A specialized company is responsible for this.

One of the fountains closed due to the legionella outbreak in Cáceres. |

Symptoms of legionellosis

The bacteria Legionella pneumophila can cause two forms of disease: non-pulmonary (or Pontiac fever) or pulmonary.

“Non-pulmonary” form:

We are talking about an acute infection that manifests itself with symptoms that could be confused with those of the flu and that resolves spontaneously.

Its incubation period ranges between 2 and 48 hours, it subsides after 2 to 5 days and the most common symptoms include:

  • Fever
  • Shaking chills
  • Headache
  • General discomfort
  • Muscle pain

The pulmonary form, also called legionellosis:

It has an incubation period of 2 to 10 days, although cases have been recorded in which it has been extended up to 16 days, and the initial symptoms include:

  • Fever
  • Loss of appetite
  • Headache
  • General discomfort
  • Lethargy
  • Muscle pain
  • Diarrhea
  • Confusion


The legionella infection requires hospital admission (due to the pneumonia it produces) and treatment with antibiotics, 10 to 15 days. Possible complications of the disease include respiratory insufficiency and, in the worst case, death.

The prognosis, emphasizes Dr. Julio García, “is better the sooner the infection is detected (by urine sample or PCR).”

Legionella prefers summer temperatures for its proliferation |

Respiratory diseases have a high mortality impact, with a average of 43.6 deaths per 100,000 inhabitants. They were the third most common cause of death in Europe as a whole, behind cardiovascular diseases and cancer.

Spain, one of the countries with the most cases of legionella

Our country is, together with France, Germany and Italyone of the European countries with the most diagnosed cases of legionella.

According to the latest report prepared by the European Center for Disease Prevention and Control (ECDC), in 2021 these countries accounted for 75% of all reported cases (10,700) and 704 deaths. Thus, the rate is 2.4 cases per 100,000 inhabitants. The most affected group, those over 65 years of age (8.9 cases per 100,000 inhabitants).

And the explanation is very simple: “it especially affects Mediterranean countries and the need to be refrigerated.” Legionella likes summer temperatures (and more so in areas like Extremadura), and its proliferation is due to the greater use of water and the use of air conditioners that help the dispersion of these bacteria and the subsequent contagion.