Sean Weaver, DO MPH
Emergency Medicine Resident
The last two years have shown high levels of national influenza activity. As we enter influenza season for 2015-2016 it is worth discussing vulnerable populations, the economic impact, prevention and treatment strategies and review the current surveillance programs.
At Risk Population
In the United States there are approximately 36,000 influenza related deaths and over 200,000 influenza related hospitalizations annually [1]. These numbers vary each year and depend on multiple factors including circulating influenza strain and vaccination rates. The elderly populations, defined as those ≥ 65 years old, bear a disproportionate burden of influenza disease. They account for nearly 90% of influenza-associated deaths [2]. They also have a higher rate of hospitalization and acute respiratory failure, regardless of associated co-morbidities [3-7].
Independent of high-risk medical conditions, increased time to hospitalization and increased age are mortality risk factors in patients with influenza. Hospitalized cases admitted more than 2 days after onset of illness had 2.17 higher odds of ICU admission or death when compared to those who were admitted within two days of illness onset [8].
Emergency Medicine Resident
The last two years have shown high levels of national influenza activity. As we enter influenza season for 2015-2016 it is worth discussing vulnerable populations, the economic impact, prevention and treatment strategies and review the current surveillance programs.
At Risk Population
In the United States there are approximately 36,000 influenza related deaths and over 200,000 influenza related hospitalizations annually [1]. These numbers vary each year and depend on multiple factors including circulating influenza strain and vaccination rates. The elderly populations, defined as those ≥ 65 years old, bear a disproportionate burden of influenza disease. They account for nearly 90% of influenza-associated deaths [2]. They also have a higher rate of hospitalization and acute respiratory failure, regardless of associated co-morbidities [3-7].
Independent of high-risk medical conditions, increased time to hospitalization and increased age are mortality risk factors in patients with influenza. Hospitalized cases admitted more than 2 days after onset of illness had 2.17 higher odds of ICU admission or death when compared to those who were admitted within two days of illness onset [8].
Economic Impact of Influenza
Influenza has a significant economic impact. The total economic burden of influenza has been estimated at $87.1 billion, 64% of which was borne by those ≥ 65 years old. Approximately $4.2 billion (40% of direct medical costs associated with influenza) was spent treating patients ≥ 65 years of age. Furthermore, of the total economic burden by health outcome, when estimating an annual death rate of 41,008 patients, accounted for $72.2 billion (83% of the total economic burden) [9]. Recognizing that the elderly have a higher rate of hospitalization and significantly higher mortality rate than other populations leaves them responsible for a disproportionately large economic burden.
Prevention and Treatment Strategies
Vaccination is a mainstay of influenza prevention. Unfortunately individuals ≥ 65 years old cannot mount the same immune response as their younger counterparts and the vaccination is less effective at preventing serious disease [10]. A Cochrane Review found poor quality of evidence regarding the safety, efficacy or effectiveness of influenza vaccine in people ≥ 65 years old [11].
If influenza cannot be adequately prevented in the high-risk elderly population then surely it can be treated? Unfortunately the answer to that question is of significant debate. The best evidence regarding the use of neuramididase inhibitors (NAI) for influenza comes from the Post-pandemic Review of anti-Influenza Drug Effectiveness (PRIDE). This consortium determined that NAI yielded greatest mortality benefit when given to patients within 48 hours of symptom onset and to those who were admitted to the ICU. A main limitation of this study though was that only a single Influenza A H1N1 strain was studied and it is unclear if these results can be extrapolated to other influenza strains [12]. Regardless, our ability to treat influenza is limited and core public health measures such as early detection, hand washing, vaccinations and social spacing are critical to limiting the spread of seasonal influenza [13].
Influenza Surveillance
The Center for Disease Control currently operates multiple influenza surveillance programs. All surveillance programs are nicely summarized in this single web page:
http://www.cdc.gov/flu/weekly/overview.htm#Outpatient. Weekly data can be found at the follow website: http://www.cdc.gov/flu/weekly/. What follows is a brief summary of some of the ongoing surveillance programs.
Outpatient illness surveillance is conducted via the US Outpatient Influenza Like Illness Surveillance Network (ILINet). ILINet data produces a weekly jurisdiction-level measure of influenza like illness (ILI) activity compared to a national and regional specific baseline data [6].
Mortality surveillance is conducted through three separate systems. 122 Cities Mortality Reporting System tracks the total number of deaths due to pneumonia or influenza. If there is an increase above baseline of 1.645 standard deviations then the epidemic threshold has been met. The National Center for Health Statistics (NCHS) Pneumonia and Influenza (P&I) mortality surveillance data is gathered from death certificates from stat vital statistics office. In 2014-2015 the use of NCHS P&I data was pilot tested for the rapid assessment of influenza-associated mortality. Finally the Influenza-Associated Pediatric Mortality Surveillance System tracks influenza-associated deaths in patients < 18 years old (link here).
Finally, FluSurv-Net acts as a population-based surveillance mechanism to detect laboratory confirmed influenza-associated hospitalizations in patient patients of all ages. States currently participating include California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon and Tennessee [6]. Of course this information is only as useful as the number of tests that are performed. Something that is uncommonly done in the emergency department setting.
These programs provide a national perspective regarding the outpatient ILI activity level, mortality and hospitalization rates of patients in the United States. While broad, these systems fail to provide real time data back to emergency medicine physicians.
Areas for Improvement
Early detection is essential in preventing influenza related deaths in the elderly. Possible areas of study include ambulance based syndromic surveillance. Targeted assisted living facility, retirement community and skilled nursing facility surveillance may also yield sentinel information that could assist providers in preventing influenza morbidity and mortality.
While the CDC surveillance programs are robust, they contain information that doesn’t necessarily translate into bedside changes in patient care. In the emergency department setting the more information we can gather the higher quality, more focused care we can provide. Future efforts could focus on getting geographic specific information to the provider in real time. This could assist with cohorting, allocation of resources, management of emergency department flow and expeditious care.
Summary
Influenza accounts for a large amount of morbidity and mortality in the United States. Unfortunately older adults bear a significant burden of disease. Influenza has a significant economic burden and strains the health care infrastructure. Vaccination, the mainstay of influenza prevention, is not as effective in older adults and other mainstays of treatment like early detection, hand washing, social distancing are the most effective prevention tools. While surveillance at the national level is robust, this information does not translate into bedside emergency department care. Further study is needed to narrow this gap and help get emergency physicians the information they need to prevent and treat outbreaks of influenza among this vulnerable population.
References
Influenza has a significant economic impact. The total economic burden of influenza has been estimated at $87.1 billion, 64% of which was borne by those ≥ 65 years old. Approximately $4.2 billion (40% of direct medical costs associated with influenza) was spent treating patients ≥ 65 years of age. Furthermore, of the total economic burden by health outcome, when estimating an annual death rate of 41,008 patients, accounted for $72.2 billion (83% of the total economic burden) [9]. Recognizing that the elderly have a higher rate of hospitalization and significantly higher mortality rate than other populations leaves them responsible for a disproportionately large economic burden.
Prevention and Treatment Strategies
Vaccination is a mainstay of influenza prevention. Unfortunately individuals ≥ 65 years old cannot mount the same immune response as their younger counterparts and the vaccination is less effective at preventing serious disease [10]. A Cochrane Review found poor quality of evidence regarding the safety, efficacy or effectiveness of influenza vaccine in people ≥ 65 years old [11].
If influenza cannot be adequately prevented in the high-risk elderly population then surely it can be treated? Unfortunately the answer to that question is of significant debate. The best evidence regarding the use of neuramididase inhibitors (NAI) for influenza comes from the Post-pandemic Review of anti-Influenza Drug Effectiveness (PRIDE). This consortium determined that NAI yielded greatest mortality benefit when given to patients within 48 hours of symptom onset and to those who were admitted to the ICU. A main limitation of this study though was that only a single Influenza A H1N1 strain was studied and it is unclear if these results can be extrapolated to other influenza strains [12]. Regardless, our ability to treat influenza is limited and core public health measures such as early detection, hand washing, vaccinations and social spacing are critical to limiting the spread of seasonal influenza [13].
Influenza Surveillance
The Center for Disease Control currently operates multiple influenza surveillance programs. All surveillance programs are nicely summarized in this single web page:
http://www.cdc.gov/flu/weekly/overview.htm#Outpatient. Weekly data can be found at the follow website: http://www.cdc.gov/flu/weekly/. What follows is a brief summary of some of the ongoing surveillance programs.
Outpatient illness surveillance is conducted via the US Outpatient Influenza Like Illness Surveillance Network (ILINet). ILINet data produces a weekly jurisdiction-level measure of influenza like illness (ILI) activity compared to a national and regional specific baseline data [6].
Mortality surveillance is conducted through three separate systems. 122 Cities Mortality Reporting System tracks the total number of deaths due to pneumonia or influenza. If there is an increase above baseline of 1.645 standard deviations then the epidemic threshold has been met. The National Center for Health Statistics (NCHS) Pneumonia and Influenza (P&I) mortality surveillance data is gathered from death certificates from stat vital statistics office. In 2014-2015 the use of NCHS P&I data was pilot tested for the rapid assessment of influenza-associated mortality. Finally the Influenza-Associated Pediatric Mortality Surveillance System tracks influenza-associated deaths in patients < 18 years old (link here).
Finally, FluSurv-Net acts as a population-based surveillance mechanism to detect laboratory confirmed influenza-associated hospitalizations in patient patients of all ages. States currently participating include California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon and Tennessee [6]. Of course this information is only as useful as the number of tests that are performed. Something that is uncommonly done in the emergency department setting.
These programs provide a national perspective regarding the outpatient ILI activity level, mortality and hospitalization rates of patients in the United States. While broad, these systems fail to provide real time data back to emergency medicine physicians.
Areas for Improvement
Early detection is essential in preventing influenza related deaths in the elderly. Possible areas of study include ambulance based syndromic surveillance. Targeted assisted living facility, retirement community and skilled nursing facility surveillance may also yield sentinel information that could assist providers in preventing influenza morbidity and mortality.
While the CDC surveillance programs are robust, they contain information that doesn’t necessarily translate into bedside changes in patient care. In the emergency department setting the more information we can gather the higher quality, more focused care we can provide. Future efforts could focus on getting geographic specific information to the provider in real time. This could assist with cohorting, allocation of resources, management of emergency department flow and expeditious care.
Summary
Influenza accounts for a large amount of morbidity and mortality in the United States. Unfortunately older adults bear a significant burden of disease. Influenza has a significant economic burden and strains the health care infrastructure. Vaccination, the mainstay of influenza prevention, is not as effective in older adults and other mainstays of treatment like early detection, hand washing, social distancing are the most effective prevention tools. While surveillance at the national level is robust, this information does not translate into bedside emergency department care. Further study is needed to narrow this gap and help get emergency physicians the information they need to prevent and treat outbreaks of influenza among this vulnerable population.
References
- Smith NM, Bresee JS, Shay DK, et al. Prevention and Control of Influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2006;55(RR-10):1-42.
- Estimates of deaths associated with seasonal influenza --- United States, 1976-2007. MMWR Morb Mortal Wkly Rep. 2010;59(33):1057-62.
- Mullooly JP, Bridges CB, Thompson WW, et al. Influenza- and RSV-associated hospitalizations among adults. Vaccine. 2007;25(5):846-55.
- Zhou H, Thompson WW, Viboud CG, et al. Hospitalizations associated with influenza and respiratory syncytial virus in the United States, 1993-2008. Clin Infect Dis. 2012;54(10):1427-36.
- Arriola CS, Brammer L, Epperson S, et al. Update: influenza activity - United States, September 29, 2013-February 8, 2014. MMWR Morb Mortal Wkly Rep. 2014;63(7):148-54.
- Epperson S, Blanton L, Kniss K, et al. Influenza activity - United States, 2013-14 season and composition of the 2014-15 influenza vaccines. MMWR Morb Mortal Wkly Rep. 2014;63(22):483-90.
- Ortiz JR, Neuzil KM, Rue TC, et al. Population-based incidence estimates of influenza-associated respiratory failure hospitalizations, 2003 to 2009. Am J Respir Crit Care Med. 2013;188(6):710-5.
- Nickel KB, Marsden-haug N, Lofy KH, et al. Age as an independent risk factor for intensive care unit admission or death due to 2009 pandemic influenza A (H1N1) virus infection. Public Health Rep. 2011;126(3):349-53.
- Molinari NA, Ortega-sanchez IR, Messonnier ML, et al. The annual impact of seasonal influenza in the US: measuring disease burden and costs. Vaccine. 2007;25(27):5086-96.
- Hernandez-vargas EA, Wilk E, Canini L, et al. Effects of aging on influenza virus infection dynamics. J Virol. 2014;88(8):4123-31.
- Jefferson T, Di pietrantonj C, Al-ansary LA, Ferroni E, Thorning S, Thomas RE. Vaccines for preventing influenza in the elderly. Cochrane Database Syst Rev. 2010;(2):CD004876.
- Muthuri SG, Venkatesan S, Myles PR, et al. Effectiveness of neuraminidase inhibitors in reducing mortality in patients admitted to hospital with influenza A H1N1pdm09 virus infection: a meta-analysis of individual participant data. Lancet Respir Med. 2014;2(5):395-404.
- Shim E. Optimal strategies of social distancing and vaccination against seasonal influenza. Math Biosci Eng. 2013;10(5-6):1615-34.
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