Participants assigned to the usual care group will receive the general practitoner's usual care of adults (≥ 18 years) presenting with symptoms of an acute lower respiratory tract infection (LRTI) where the GP suspects community-acquired pneumonia. Usual care will be used as a pragmatic comparator to reflect the current standard examinations and care of this patient population in general practices in Denmark. Usual care is recommended to follow applicable guidelines from the Danish Society of General Practitioners and The Doctor's Handbook. Focused lung ultrasound (FLUS) is currently not standard or even a common examination in Danish general practices. Even for GPs already using point-of-care ultrasound on a weekly basis, FLUS is not part of usual care for adults presenting with symptoms of an acute LRTI

Participants assigned to the intervention group will receive a focused lung ultrasound examination (FLUS) during the index consultation (day 0) as an addition to usual care.

We will use a 14-zone scanning approach. Each hemithorax is divided into anterior, lateral, and posterior surfaces. The anterior and lateral surfaces on each hemithorax are divided into an upper and lower quadrant. The posterior surfaces on each hemithorax are divided into an upper, middle, and lower quadrant. Each quadrant represents a scanning zone. Each scanning zone should be assessed using FLUS. The participating general practitioners use point-of-care ultrasound on a weekly basis before trial commencement and will use the ultrasonography device already available to them.

The primary outcome is the proportion of participants with antibiotics prescribed at index consultation (day 0) reported by the GP at index consultation. We will assess the effect of adding FLUS to usual care on antibiotics prescribed at index consultation by investigating if there is a difference between groups in the proportion of participants with antibiotics prescribed at index consultation..

Daily total LRTI symptom-score in groups, calculated as sum of scores of six symptoms (minimum 0 - maximum 36) (mean/median). Participants will be asked to complete a validated LRTI symptom diary every day from day 0 up until day 21. The recorded items include the following six symptoms of LRTI: cough, dyspnea, sputum production, well-being, sleep disturbance, and activity disturbance. The participants will be asked to consider how bad each symptom has been, over the past 24 hours by scoring each symptom on a 7-point Likert-scale (0 = no problem, 1 = very little problem, 2 = slight problem, 3 = moderate problem, 4 = bad problem, 5 = very bad problem, and 6 = as bad as it could be).