Legionnaires’ disease is treated with antibiotics, and the earlier they start, the better people tend to do. Because it is a serious lung infection, many people need treating in hospital, and the most unwell may need extra oxygen, antibiotics given through a drip, or a spell in intensive care [1].

It is not an infection to ride out at home and hope it passes. Left untreated, or treated late, it can become dangerous, which is why getting a diagnosis and starting the right drug quickly is the whole game [2].

If you are reading this because you or someone close to you has just been diagnosed, or is waiting to be seen, the sections below explain what treatment usually involves. None of it replaces what your own clinician tells you.

Antibiotics are the mainstay

The core of Legionnaires’ disease treatment is a course of antibiotics [1]. The illness is a bacterial pneumonia caused by Legionella, and antibiotics are what clear the infection. There is no home remedy, no over-the-counter fix, and rest alone will not shift it.

For people who are only mildly affected and caught early, treatment can sometimes be antibiotics taken by mouth at home, under medical supervision. But Legionnaires’ is often more severe than an ordinary chest infection, so a hospital stay with antibiotics given intravenously is common, particularly for older people or those with other health conditions [1].

The single most useful thing to understand is timing. Early antibiotic treatment improves outcomes, which is exactly why a worsening chest infection should not be left for days “to see if it settles” — especially if there is any chance of exposure to water mist from showers, spa pools or air-conditioning systems [2]. If you are still at the symptom-checking stage, Legionnaires’ disease symptoms and when to see a doctor covers the warning signs and the point at which to ring for help.

Why the right diagnosis changes the antibiotic

Here is the part that surprises people, and it is the reason an accurate diagnosis matters so much.

Legionella is what doctors call an “atypical” cause of pneumonia. It behaves differently from the common bacteria behind most chest infections, and crucially, several antibiotics routinely prescribed for ordinary pneumonia do not reliably work against it [2]. A drug that would clear a typical chest infection can leave a Legionella infection to carry on.

So clinicians choose from antibiotic classes known to be effective against Legionella specifically. Which drug, dose and route they use is a clinical decision based on how ill the person is, their other conditions and local prescribing guidance — not something to self-prescribe or read off the internet.

The practical takeaway for a patient is simple. Tell the clinician if you think you may have breathed in water mist recently, and where. That one piece of context can steer them toward testing for Legionella and choosing an antibiotic that targets it, rather than one that treats the more common kind of pneumonia and misses this. The resistance and prescribing picture, viewed from the water-safety side, is covered in Antibiotic treatment and resistance in Legionella.

Hospital, oxygen and intensive care

Legionnaires’ disease can be severe, and a meaningful share of people who get it end up in hospital [3]. What hospital treatment adds, beyond the antibiotics, is support for the body while the infection is brought under control.

That support can include extra oxygen if blood-oxygen levels drop, fluids given through a drip, and close monitoring of the lungs, kidneys and other organs. The most seriously affected may need intensive care, sometimes with help breathing, because the pneumonia can hit lung function hard enough that the body cannot keep up on its own [1].

How likely any of this is depends a lot on the person. Older adults, smokers, and people with weakened immune systems or long-term lung, kidney or other conditions tend to be affected more severely [3]. For an honest picture of how serious it can become, Is Legionnaires’ disease fatal? sets out mortality, severity and outcomes.

Recovery can be slow

Getting the infection under control is not the same as feeling well again. Recovery from Legionnaires’ disease is often slow, and tiredness in particular can linger for weeks or even months after the antibiotics have done their job [1].

People are sometimes caught off guard by this. They expect to bounce back the way you might from a heavy cold, and instead find that fatigue, breathlessness on exertion, and a general lack of energy hang around well after they have left hospital. That is a recognised part of recovering from this kind of pneumonia, not a sign that treatment failed.

Completing the full antibiotic course, following up with your GP, and giving yourself real time to recover all matter. Legionnaires’ disease incubation period and recovery time goes into the recovery timeline in more detail.

This page is general information, not medical advice and not a diagnosis. Treatment decisions — which antibiotic, for how long, at home or in hospital — belong to a qualified clinician who can examine the person and read their test results. If you are unwell, contact NHS 111 or your GP, and call 999 or go to A&E if breathing becomes severely difficult or someone becomes very confused or hard to rouse.

What to do now

If you or someone you are with has a cough, fever and shortness of breath that is getting worse, the next step is not to wait. Contact NHS 111 or your GP today, and mention any chance you breathed in water mist — from a shower, hot tub, spa pool or an unfamiliar building’s water — in the past fortnight.

Before you call, jot down when the symptoms started and where you might have been exposed. It takes two minutes and gives whoever assesses you a head start on the right test and the right antibiotic.

Common questions about treatment

Can Legionnaires’ disease be treated at home?

Sometimes. For mild cases caught early, a clinician may prescribe oral antibiotics to take at home with follow-up. But Legionnaires’ is frequently severe enough to need hospital care, including intravenous antibiotics and oxygen [1]. Whether home treatment is safe is a judgement only a clinician can make after assessing you — not a decision to take yourself.

Why don’t ordinary chest-infection antibiotics work?

Because Legionella is an “atypical” pneumonia bacterium that behaves differently from the common causes of chest infections. Some antibiotics routinely given for ordinary pneumonia do not reliably clear it, so doctors choose from classes known to be effective against Legionella [2]. This is why telling your clinician about possible water-mist exposure helps them test for and target the right organism.

How long does antibiotic treatment last?

The length of a course is decided case by case, based on how ill the person is and how they respond, so there is no single fixed duration to quote here. What matters is taking the full course exactly as prescribed and not stopping early just because you feel better. Your clinician will tell you how long yours should run and arrange any follow-up.

Can you fully recover from Legionnaires’ disease?

Many people recover well, particularly when treatment starts early, but recovery can be slow and tiredness may persist for weeks or months [1]. Those who were very unwell, or who are in higher-risk groups, can take longer or have lasting effects [3]. Your recovery time and any ongoing care are best discussed with the team treating you.

Sources

[1] NHS, “Legionnaires’ disease”. https://www.nhs.uk/conditions/legionnaires-disease/ [2] CDC, “About Legionnaires’ Disease”. https://www.cdc.gov/legionella/about/index.html [3] UKHSA, “Legionellosis in residents of England and Wales: 2024”. https://www.gov.uk/government/statistics/legionellosis-in-residents-of-england-and-wales-2024/legionellosis-in-residents-of-england-and-wales-2024