There have been a number of recommendations published that define when antibiotics should be prescribed in rhinosinusitis (2-5). The most common accepted strategy is for antibiotics to be prescribed when symptoms have been present for 7-10 days, and preferably if the symptoms have been unimproving or worsening over that time period. This is due to research which has shown that rhinovirus infections cause fever and some sore throat which subsides in the first week, while other symptoms such as cough and nasal drainage gradually resolve over two weeks (6). More severe viruses such as respiratory syncytial virus and influenza A tend to cause worse and more prolonged symptoms. Therefore, it is important when trying to identify likely bacterial sinus infections to not look solely at the duration of the symptoms, but also to give consideration to the course of infection, whether it is improving, not changing or worsening. The latter two situations tend to correlate with a greater likelihood for a shift from a viral to bacterial infection.

In the context of antimicrobial therapy, chronic rhinosinusitis is usually considered to be persistent bacterial infection, but this is certainly not always the case. For example, most patients with chronic rhinosinusitis do not have bacterial infections, but many other processes are involved. These include recurrent upper respiratory tract infections (URTIs), allergies, and headache. Only a subgroup of patients with chronic rhinosinusitis has true bacterial infection. This has led to a call to abandon the use of the term chronic rhinosinusitis and to use a more specific definition of disease.