Viral Infections
A New Framework for Influenza – Rational Use of Antiviral Therapy and Vaccines
Amesh A Adalja Associate, Center for Biosecurity of University of Pittsburgh Medical Center
Abstract
Seasonal influenza is a major health burden worldwide and pandemics have the capacity to stress the healthcare system severely. During the last pandemic of influenza in 2009 – the first in decades – many new tools were utilised in the management of influenza. The employment of these resources constitutes a new paradigm and framework for understanding and responding to both seasonal and pandemic influenza.
Keywords Influenza, vaccine, antivirals
Disclosure: Amesh A Adalja is a shareholder of Biocryst Pharmaceuticals. Received: 15 December 2010 Accepted: 11 April 2011 Citation: European Infectious Disease, 2011;5(2):115–7 Correspondence: Amesh A Adalja, Center for Biosecurity of UPMC, The Pier IV Building, 621 E Pratt Street, Suite 210, Baltimore, MD 21202, US. E:
aadalja@upmc-biosecurity.org
Influenza kills approximately 3,000 to 49,000 Americans per year1
and the
potential for a pandemic – as seen in 1918, 1957, 1968 and 2009 – looms large and has prompted the US government, healthcare facilities and healthcare workers to undertake extensive pandemic preparation. Activities include hospital planning, vaccination schedules, as well as antiviral medication stockpiling. To this last end, the US government has developed a Strategic National Stockpile (SNS) of antiviral medications for use during a pandemic for treatment as well as prophylaxis.
Moreover, the current state of resistance of both H1N1 and H3N2 influenza A isolates to various classes of drugs has become cumbersome for clinicians to comprehend and the knowledge of some virulence-enhancing features of influenza strains is not well known to clinicians. This review will present some of the most important new developments in the clinical management of influenza.
Current Clinical Practice for Testing and Treating Influenza Testing
Most hospitals have the availability, on-site, for rapid detection of influenza A or B virus antigens from nasopharyngeal swabs and some larger institutions use highly sensitive polymerase chain reaction (PCR)-based methods. Yet many clinicians do not use these tests for a variety of reasons, including a perceived lack of effect on medical decision-making.3
However, clinical practice with seasonal influenza is varied and falls short of the competence needed in a pandemic or severe seasonal outbreak, as evidenced by several cases in which antiviral therapy administration to patients was delayed during the 2009 H1N1 pandemic.2
hospitals outsource their influenza testing to bigger hospitals or laboratories (eliminating the availability of real-time results).
Several factors – other than the relative insensitivity of rapid antigen testing – are overlooked for the reasons cited to forgo rapid testing.
• •
The ability to distinguish clinical cases of influenza from other respiratory viral illnesses is poor.4
What may or may not be labelled ‘influenza’ could be another similar illness.
If a patient presents outside the treatment window, they remain infectious and diagnosis of influenza will influence isolation procedures (if the patient is admitted) or prophylaxis decisions for household contacts (e.g. cohabitation with an immunosuppressed individual). Of note, a nosocomial case of influenza is responsible for US$3,800 in extra charges per patient.5
• •
Data indicate that oseltamivir, given outside the 48-hour window, can prevent some of the serious sequelae of influenza infection as well as reduce shedding of the infectious virus.6
A diagnosis of influenza can often delimit a work-up for illness by providing a diagnosis and prevent the unnecessary prescription of antibiotics, even when tests without 100 % sensitivity are utilised.7,8
Treating
Prior to the 2009 H1N1 pandemic, the use of antiviral therapy for influenza infections was relatively low in the US.9
With the data
Indeed, Centers for Disease Control and Prevention (CDC) recommendations reinforce that testing should be done only when it will affect medical decision-making. Also, given the 48-hour window for maximal antiviral efficacy, many people fail to present rapidly enough to receive maximum benefit from treatment, making diagnosis seem somewhat superfluous. Additionally, some small
© TOUCH BRIEFINGS 2011
accumulated during the pandemic, guidelines have now become more supportive of the use of antiviral drugs and clinicians are now more familiar with the options for treatment. Current guidelines for the 2010–2011 influenza season emphasize certain high-risk groups who should always receive antiviral treatment, irrespective of whether presentation is outside the 48-hour ‘window’ and other groups in whom to consider antiviral therapy (see Table 1).10
Treatment initiation should
not wait for influenza confirmation, especially in any high-risk group for which antiviral therapy is indicated.
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