It’s so unexpected that the unexplained pneumonia in Argentina turned out to be Legionella!

Recently, several cases of pneumonia of unknown cause have occurred in Tucumán Province in northern Argentina. The possibility of infection with COVID-19, influenza A and B, and a variety of common pathogens has been ruled out. As of the morning of September 3, the province has reported a total of 11 cases of pneumonia of unknown cause and 4 deaths. On the same day, Pablo Yedlin, Chairman of the Health Committee of the Argentine Senate and former Director of the Tucumán Provincial Public Health Bureau, said in an interview with the media that according to laboratory data, the cause of the pneumonia of unknown cause found in the Luz Hospital in Tucumán Province recently was Legionella.

After a long time, it turned out that it was Legionella that was causing the problem. Alas, it shouldn't take more than half a month to discover this common infection. This can also be called "Approaching Science" after three episodes, it was discovered that the body turned blue because of the fading of pants. It's really amazing. So what is Legionella? What are the infection routes of Legionella? Let's talk about it today!

01. What is Legionella?

Legionella is a facultative intracellular pathogen that is commonly found in natural freshwater and artificial waters (tap water, hot showers, central air conditioning condensate, cooling tower water, etc.), or parasitizes in protozoa (such as amoebas). There are currently 50 confirmed species of Legionella. Among them, the Legionella pneumophila species is the most closely related to human diseases, and 16 serotypes have been found.

More than 30 species of Gram-negative Legionella have been discovered so far, many of which can cause human infection. The most common one is Legionella pneumophila, which can easily cause symptoms of atypical pneumonia. If not treated in time, the mortality rate is not low.

The reason why it is called Legionella is that this epidemic broke out at a veterans convention held in Philadelphia, USA in 1976. At that time, it was commemorating the 200th anniversary of the signing of the Declaration of Independence. However, this epidemic occurred, causing 221 people to become ill and 34 people to die, so it was named Legionella.

02. Infection routes of Legionella

Epidemiological surveys have found that Legionella is very common among drivers[1]. The possible cause is believed to be the windshield wiper water tank of our cars. This is because in many cases, our windshield wiper water tanks are not frequently refilled with water. Instead, they are refilled once and then stored for a long time, which results in bacteria easily growing in the water tank.

In addition, in order to save time or money, many people simply add tap water directly to the water tank[2] instead of glass water containing a lot of surfactants. This makes it easier for bacteria to multiply. After all, surfactants are more or less harmful to bacteria.

In fact, there are many similar cases in reality, such as this unlucky driver.

Legionella is actually widely distributed, but it will only cause respiratory infections after being inhaled in large quantities through aerosolization . In addition, factors such as weak health, lung disease, and older age are also risk factors for Legionella infection.

This case also reminds us that it is best to ventilate a space that has been closed and unused for a long time before entering it.

In addition, it is particularly worth noting that if the air conditioner has not been used for a long time, you should pay attention to the problem of bacterial growth.

1 Polat, Yusuf, et al. "Investigation of Legionella pneumophila seropositivity in the professional long distance drivers as a risky occupation." Mikrobiyoloji bulteni41.2 (2007): 211-217.

2 Jurčev-Savičević, Anamarija, et al. "Bus water storage tank as a reservoir of Legionella pneumophila." Collegium antropologicum38.3 (2014): 1033-1037.