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Are there differences in symptoms between viral and bacterial respiratory tract infections that doctors could use to distinguish between the two types of infection and thus reduce antibiotic over prescribing?

In primary care patients who have a lower respiratory tract infection, there may be differences in symptom severity between those whose have a viral infection and those who have a bacterial infection, according to a recently published study.

The study, published in the journal Family Practice and led by researchers from the University of Oxford, examined throat swabs from 645 patients in 13 primary care practices who presented to their doctors with a cough and other symptoms.

Swabs were tested using Polymerase Chain Reaction – a highly sensitive method of analysing DNA – for the presence of different pathogens, and the symptoms of those patients in whom a virus was detected were compared with those in whom bacteria were detected. Patients recorded their symptoms initially and during the week after they visited their GP surgery.

The results showed that patients with a viral infection presented sooner to their GPs, and were more likely to have certain symptoms, such as a blocked or runny nose, or muscle aches with audible crackles in their lungs when breathing. Two-thirds of these patients received a prescription for antibiotics, even though antibiotics are ineffective for viral infections.

Compared with patients in whom no specific organism could be detected, those with a virus and those with the Haemophilus influenzae bacterium reported slightly more severe symptoms during the week after consultation. Patients with a combined viral and bacterial infection had the highest average symptom severity.

The average duration of illness was similar regardless of the type of organism detected, with most patients having only mild symptoms within one week of seeing their GP, or around two weeks after their symptoms first appeared.

First author Dr Jose Ordonez-Mena, Medical Statistician at the Nuffield Department of Primary Care Health Sciences, summarised: “Although we found differences between some organism groups in the presence of symptoms and their severity, these differences by themselves are probably not large enough to allow doctors to differentiate between viral and bacterial infections.”

The study only looked at patients’ symptoms within one week after consultation, so was unable to assess those with prolonged illness. It was also unable to assess symptoms of rarer specific bacteria and viruses that might lead to worse prognosis, as these were not detected often enough in the group of patients to allow conclusions to be drawn.

Senior Investigator Dr Kyle Knox, a general practitioner, commented: “Most patients who came to their GP with a respiratory tract infection had only mild symptoms after one week, which could inform patients about the likely duration of their symptoms. Usually decisions about prescribing antibiotics are made without knowledge of the organism that is causing the infection and this study shows that clinical signs and symptoms cannot reliably identify infections that may respond to antibiotics. In the future, rapid point of care tests may help clinicians refine their clinical assessments and lead to more accurate diagnoses.

The study was funded by the National Institute for Health Research School for Primary Care Research, and the principal investigators also received funding from the NIHR Community Healthcare MedTech and In Vitro Diagnostics Co-operative and the NIHR Oxford Biomedical Research Centre.

Relationship between microbiology of throat swab and clinical course among primary care patients with acute cough: a prospective cohort study
José M Ordóñez-Mena, Thomas R Fanshawe, Chris C Butler, et al
Family Practice, cmz093,


Virus and bacteria images created by brgfx -