legionaires

Clinical answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

Legionnaires' disease is a severe form of pneumonia caused by Legionella pneumophila, often presenting as an atypical pneumonia . It can manifest with a range of symptoms beyond typical respiratory complaints.

Clinical Presentation:

Symptoms of lower respiratory tract infection (LRTI) are common, including cough, fever, sputum production, breathlessness, wheeze, or chest discomfort/pain ,.
Legionnaires' disease can also present with non-pulmonary symptoms such as gastrointestinal issues (e.g., diarrhoea, nausea, vomiting), neurological symptoms (e.g., confusion, headache), and hyponatremia .

Diagnosis:

A clinical diagnosis of community-acquired pneumonia (CAP) is based on symptoms and signs of LRTI ,.
For people presenting with LRTI, a risk assessment using the CRB65 scoring system should be carried out if a clinical diagnosis of pneumonia has been made ,. The CRB65 score assigns 1 point for each of: confusion (Abbreviated Mental Test score 8 or less, or new disorientation), raised respiratory rate (30 breaths per minute or more), low blood pressure (diastolic 60 mmHg or less, or systolic less than 90 mmHg), and age 65 years or more ,.
For people with moderate- or high-severity CAP, consider pneumococcal and Legionella urinary antigen tests, in addition to taking blood and sputum cultures . Microbiological tests are not routinely offered for low-severity CAP .
If it is unclear whether antibiotics are needed for someone with an LRTI, a point-of-care C-reactive protein (CRP) test can support clinical decision-making: offer immediate antibiotics if CRP is more than 100 mg/litre, consider a back-up antibiotic prescription if CRP is between 20 mg/litre and 100 mg/litre, and do not routinely offer antibiotics if CRP is less than 20 mg/litre .

Management:

Decisions about hospital assessment for people with a clinical diagnosis of CAP should be informed by clinical judgement and the CRB65 score ,:
- Consider hospital assessment for a CRB65 score of 2 or more ,.
- Discuss options and make a shared decision about care pathways (e.g., supported home-based care) for a score of 1 ,.
- Consider home-based care for a score of 0 ,.
For antibiotic therapy, specific recommendations for community-acquired pneumonia should be followed . Levofloxacin, a quinolone, is indicated for respiratory system infections and is often used in the treatment of Legionnaires' disease (Levofloxacin SmPC ; ML & M, 2005; BA et al., 2016; A & SM, 2017).

Key References

Related Knowledge Topics