While early stage influenza can be indistinguishable from the common cold, and modern medicine has become incredibly efficient at diagnosing and treating the condition, influenza still has the ability to develop rapidly, endangering infected individuals if left unchecked.
Severe influenza presents unique challenges for clinicians. While mild influenza can be treated via ambulatory care, patients who develop complications could get severe influenza which can result in hospital and even ICU admission. Infants, the elderly and sufferers of chronic disease are most at risk of severe influenza, as it can result in complications and exacerbations of underlying conditions([FOOTNOTE=Choi WS, Baek JH, Seo YB, et al. Severe influenza treatment guideline. The Korean Journal of Internal Medicine. 2014;29(1):132-147. doi:10.3904/kjim.2014.29.1.132.],[ANCHOR=],[LINK=]). In the UK, children under 5 have the highest influenza admission rate (1.9 per 1000), while over two-thirds (72%) of all influenza-attributable deaths in hospital occurred in patients over the age of 65 who had co-morbidities.([FOOTNOTE=Cromera D, Jan van Hoek A, Jit M, Edmunds WJ, Fleming D, Miller E. The burden of influenza in England by age and clinical risk group: A statistical analysis to inform vaccine policy. Journal of Infection, Vol 68, Issue 4. April 2014, Pages 363-371. doi: 10.1016/j.jinf.2013.11.013],[ANCHOR=],[LINK=])
According to World Health Organisation (WHO) guidelines([FOOTNOTE=World Health Organization. WHO guidelines for pharmacological management of pandemic (H1N1) 2009 influenza and other influenza viruses [Internet] Geneva (CH): World Health Organization; c2013. Available from: http://www.who.int/csr/resources/publications/swineflu/h1n1_use_antivirals_20090820/en/],[ANCHOR=],[LINK=]), severe influenza is defined as a positive influenza test result combined with at least one of the following clinical presentations:
The most common are rapid influenza diagnostic tests (RIDTs) which detect influenza antigens. These tests produce results within 10-15 minutes([FOOTNOTE=https://www.cdc.gov/flu/professionals/diagnosis/clinician_guidance_ridt.htm],[ANCHOR=],[LINK=]) but are not entirely accurate. Rapid molecular assays swab and analyse respiratory tract mucus and are more accurate than RIDTs, but take longer to produce results (15-20 minutes)([FOOTNOTE=https://www.cdc.gov/flu/professionals/diagnosis/molecular-assays.htm],[ANCHOR=],[LINK=]). These tests, in concert with physical examination, are generally enough for a clinician to confidently diagnose influenza.
As severe influenza can present in the wide variety of ways listed above, a patient’s treatment will focus on minimising symptoms, and will be guided by their clinical presentations. Antibiotics may be administered if the patient has accompanying pneumonia, sinusitis or any other bacterial infection, and various treatments aiming to oxygenate the body may be employed if the patient presents with pulmonary issues. How these treatments might interact with the antiviral medications must be carefully considered before being prescribed.([FOOTNOTE=Leekha S, Zitterkopf NL, Espy MJ, et al. Duration of influenza A virus shedding in hospitalized patients and implications for infection control. Infect Control Hosp Epidemiol. 2007; 28(9):1071-6.],[ANCHOR=],[LINK=])