In order to estimate the cost of influenza, we have to consider a number of ways in which flu adds to the burden on our economy and society.
These include looking at the effect of influenza on the health care system. More flu cases mean more primary care consultations and hospital admissions.
This brings direct costs in terms of time spent by medical and nursing staff caring for patients, along with the cost of medicines and hospital maintenance. In addition, we must also consider that where hospital capacity is limited, the hospitalisation of flu patients could come at the expense of other patients.
Secondly, the effect of influenza on the quality of life must be brought into the equation. Increased morbidity and mortality can have a profound effect on patients and their families.
This, in turn, brings us to another way in which the burden of flu can weigh on society: influenza can reduce economic productivity due to missed work by people who are ill or by family members who must stay at home to care for them.
Finally, we must consider the wider effect of influenza on business activity – particularly during a pandemic – as a result of reduced social contact. In typical situations, a local flu outbreak could mean fewer people frequenting restaurants, attending concerts or going shopping.
If we widen this to an extreme situation, such as a global pandemic or a new virulent strain of the flu, we might factor in a decline in air travel and even reduced international trade.
Putting numbers on the true impact of influenza – even in the areas highlighted above – is no easy task. Quantifying the burden of flu is difficult because several respiratory pathogens can cause similar symptoms at approximately the same time of the year.
Scientists collect samples from people with respiratory symptoms and test them to see if they contain the flu virus. This gives us an idea of when the flu season arrives every year.
By using statistical models t look at the way sick days – as well as GP consultations and admissions – go up at the height of the flu season, we can estimate how much of this burden may be due to the flu.
Only through an evidence-based approach to calculating the cost of flu – and the cost of interventions, such as vaccination – can we expect to make informed decisions about how best to use finite resources in the health sector.
Mark Jit, Modelling and Economics Unit, Health Protection Agency, UK
This article is adapted from a presentation given at the ESWI Fourth Influenza Conference, September 11-14.