Social and Economic Impact of Influenza
In addition to the short-term incapacitating symptoms of influenza, complications may arise from having influenza either directly and indirectly (see
- The WHO estimates that 3–5 million cases of severe influenza illness result in 250,000–500,000 deaths annually in the industrialized world.
- Compared to healthy adults, influenza-related death rates are as much as 50- to 100-fold higher among patients with cardiovascular or pulmonary disease, and even higher for those with two or more co-morbid conditions.
- In young children, influenza is associated with increased rates of otitis media and serious cardiorespiratory illnesses leading to hospitalization.
- The annual cost of influenza is highly variable and may be as high as E20 million in direct health-care costs in some European countries – these direct costs are less than 10% of the total annual cost to society.
- Work absenteeism from influenza illness results in indirect costs that may also be as high as E20 million in lost days of work in a single influenza season.
- School absenteeism not only impacts on children but contributes on average to a loss of 3 work days for the parent who must remain at home with the child.
- Intangible costs include those related to death, increased disability or a diminished quality of life for the individual and the potential additional burden to caregivers.
- The Centers for Disease Control (CDC) has estimated that in the USA, during an influenza pandemic, high-risk individuals representing 15% of the population would account for ∼84% of all deaths, at a cost of US .3–166.5 billion, excluding disruptions to commerce and society.
Epidemiological records on the morbidity and mortality statistics related to influenza show that, in the winters from 1990 to 1998, the mean annual estimate of influenza-associated deaths in the USA was 51,203, mostly associated with influenza A (H3N2). 3 x WW Thompson, DK Shay, E Weintraub, et al.. Mortality associated with influenza and respiratory syncytial virus in the United States. J Am Med Assoc 289 (2003) (179 - 186) Crossref. The death rates varied from year to year, with an average across the decade of 195 influenza-related deaths per million population ( Table 8 ).
Table 8 source: Reproduced from Thompson WW et al . Mortality associated with influenza and respiratory syncytial virus in the United States. JAMA ; 289 : 179–186 3 x WW Thompson, DK Shay, E Weintraub, et al.. Mortality associated with influenza and respiratory syncytial virus in the United States. J Am Med Assoc 289 (2003) (179 - 186) Crossref. with permission from the American Medical Association.
|Estimated annual influenza deaths rates per 100,000 in the USA (1990–1999)|
The influenza attack rate varies from year to year as does the virus strain. The annual attack rate lies between 6–12% of the population. In the USA, in recent years, an annual average of approximately 36,000 people die and 200,000 people are hospitalized due to influenza. 4 x Centers for Disease Control and Prevention (CDC). Key Facts about Influenza and Influenza Vaccine. (www.cdc.gov/flu/keyfacts.htm) Based on a total population of 298 million, these figures represent mortality and hospitalization rates of 120 and 670 per million population, respectively. The current mortality rate is thus lower than the average excess mortality in the USA during the last decade ( Table 8 ). Extrapolating the current numbers for the USA, Table 9 shows the average annual excess influenza-associated deaths and hospitalizations for a number of countries in Europe.
|Estimated averages of annual excess morbidity and mortality in Europe during influenza epidemics|
|Country||Inhabitants (millions)||Excess deaths||Excess hospitalizations|
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The influenza attack rate varies from year to year as does the virus strain.
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Population groups at higher risk
As discussed in the previous chapter, complications arising from influenza are more frequent and serious among adults with chronic conditions, such as pneumonia or respiratory disease, cardiac disease or cerebrovascular disease. 5 x KL Nichol, J Wuorenma, T von Sternberg. Benefits of influenza vaccination for low-, intermediate-, and high-risk senior citizens. Arch Intern Med 158 (1998) (1769 - 1776) Crossref. Influenza may cause secondary bacterial pneumonia and exacerbations of underlying chronic medical conditions that can result in hospitalization or even death. These groups are at a higher morbidity and mortality risk from influenza.
Death rates associated with influenza and pneumonia have been estimated as two per 100,000 for patients with no high-risk conditions, 10 per 100,000 in those with one high-risk condition and 377 per 100,000 in those with two or more high-risk conditions. 6 x R Zimmerman. Lowering the age for routine influenza vaccination to 50 years. Am Fam Physician 60 (1999) (2061 - 2066) Other studies have reported that influenza-related death rates are as high as 50 times greater in patients with cardiovascular disease, 100 times greater in patients with pulmonary disease, and even higher in those with two or more co-morbid conditions, than in healthy adults. 7 x WH Barker, JP Mullooly. A study of excess mortality during influenza epidemics in the United States, 1968–1976. Am J Epidemiol 115 (1982) (479 - 480)
Age poses an additional risk factor. Even in the absence of underlying medical conditions, the elderly are at increased risk for serious complications and possibly death due to influenza, primarily as a result of a decline in cell-mediated immunity with age, as discussed in
Children are also at increased risk for complications due to influenza, in particular small infants because of their immature immune system (see
Table 10 source: Reproduced from Neuzil KM et al . The burden of influenza illness in children with asthma and other chronic medical conditions. J Pediatr 2000; 137 : 856–864 8 x KM Neuzil, PF Wright, EF Mitchel, MR Griffin. The burden of influenza illness in children with asthma and other chronic medical conditions. J Pediatr 137 (2000) (856 - 864) Crossref. with permission from Elsevier.
|Influenza-related health-care interventions among children|
|Excess number per 1000 children|
|Hospitalizations for children:|
References in context
As with the elderly, a chronic underlying medical condition adds to the risk.
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|WW Thompson, DK Shay, E Weintraub, et al..||Mortality associated with influenza and respiratory syncytial virus in the United States. Crossref.||J Am Med Assoc 289 (2003) (179 - 186)||2003|
|Centers for Disease Control and Prevention (CDC).||Key Facts about Influenza and Influenza Vaccine.||(www.cdc.gov/flu/keyfacts.htm)|
|KL Nichol, J Wuorenma, T von Sternberg.||Benefits of influenza vaccination for low-, intermediate-, and high-risk senior citizens. Crossref.||Arch Intern Med 158 (1998) (1769 - 1776)||1998|
|R Zimmerman.||Lowering the age for routine influenza vaccination to 50 years.||Am Fam Physician 60 (1999) (2061 - 2066)||1999|
|WH Barker, JP Mullooly.||A study of excess mortality during influenza epidemics in the United States, 1968–1976.||Am J Epidemiol 115 (1982) (479 - 480)||1982|
|KM Neuzil, PF Wright, EF Mitchel, MR Griffin.||The burden of influenza illness in children with asthma and other chronic medical conditions. Crossref.||J Pediatr 137 (2000) (856 - 864)||2000|