How can we prepare better for influenza epidemics?BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5007 (Published 02 November 2017) Cite this as: BMJ 2017;359:j5007
- Chris Del Mar, professor of public health, Bond University1,
- Peter Collignon, infectious diseases physician and clinical microbiologist, Canberra Hospital, and executive director, ACT Pathology2
Public health physicians and clinicians keep a wary eye out for influenza epidemics, bearing in mind the greatest pandemic at the end of the first world war, when tens of millions died.1 The epidemics come every year, but their severity varies. Normally influenza is simply one of many clinically indistinguishable influenza-like illnesses (ILIs) from which people recover uneventfully. Australia’s latest season was worse than most, with a record number of laboratory confirmed cases (170 000), although better availability of molecular tests may account for much of the rise, as visits for ILIs have risen only slightly above the annual average.2 The northern hemisphere is now bracing for its turn.
Occasionally, influenza can cause severe illness or death, especially in elderly people. Sometimes different strains put unexpected population groups at risk (pregnant women, patients with asthma or diabetes, obese people). So what can we do to prepare for epidemics?
Three main options
The current options are vaccination, antivirals, and hygiene interventions. Most attention is on vaccination, which is curious, because its effectiveness is disappointing. Given influenza’s very low annual incidence, vaccination would bring only a drop from 2% to 1%,3 clinically imperceptible because of the much higher incidence of ILIs. Genetic drift in the virus means revaccination is needed every year with modified antigens, bringing an element of uncertainty to each year’s effectiveness. Genetic shift (especially as new virus moves from animal reservoirs to humans, with its risk of pandemic) makes vaccine effectiveness even less certain, just when protection is most needed. Vaccination seems to have been less effective recently, especially against the predominant viruses in circulation (influenza A H3 and B strains), with little or no protection in elderly patients against H3 last winter in the UK and elsewhere.45 Moreover, people who have repeat vaccinations have less protection, for unknown reasons.6 Annual vaccination (including compulsory vaccination for health workers in residential aged care facilities 78) is based on poor evidence and may be overpromoted.
Use of antiviral neuraminidase inhibitors is controversial. They reduce symptoms by about half a day in a five day illness, but any effect on secondary infections or admissions to hospital, or on spread of the virus in an epidemic, remains uncertain,9 and the World Health Organization has recently taken it off its Model List of Essential Medicines.10
Hygiene is extremely effective
Hygiene methods such as handwashing, face masks, and quarantine have been found to be extremely effective at protecting against acute respiratory infections in a Cochrane review, with numbers needed to treat as low as three.11 Why are these methods not canvassed as heavily as vaccination or antivirals? It would be facile only to blame industry promotion of drugs. Social norms, though accepting of handwashing (or sterilisation in public places), mean that people baulk at wearing face masks (except in east Asian countries such as Japan). Nor do such norms insist that people who are infectious stay away from work or school (instead, admiring them for “soldiering on”) or that mass gatherings (sports and cultural events) are cancelled. People (including clinicians) expect medical technology to be more effective than is realistic,61213 all the more reason for supporting sensible low technology policies, such as one Australian state’s intention to install hand hygiene dispensers on trains, with a campaign to promote “cough into your elbow.”14
People (including clinicians) expect medical technology to be more effective than is realistic, all the more reason for supporting sensible low technology policies
What about the threat of influenza pandemics? In 1918-19 huge numbers of troops returning home, a population exhausted from four years of war and with inadequate nutrition, and poor management of secondary bacterial infections contributed to the magnitude of the disaster. Some of these factors might have less of a role in a modern recurrence, but not others, such as a vastly more mobile population, which would render near useless any quarantine isolation of an outbreak. It is hard to see what could be done to mitigate a catastrophe that was not rehearsed in recent avian and swine flu epidemics.
In the meantime it is clear that we need better vaccines, with better evaluation, and public awareness messages that promote mask wearing and hand hygiene.15
Competing interests: CDM has received grants to his institution from Australia’s National Health and Medical Research Council (two centres for research excellence, one in antimicrobial resistance), the UK National Institute for Health Research (systematic review on neuraminidase inhibitors for influenza), the UK Health Technology Assessment programme (systematic review on neuraminidase inhibitors for influenza), a private donor (for the Cochrane Collaboration ARI Group), and the Australian Commission on Safety and Quality in Health Care (for the provision of decision aids and an education module on risk communication).