InfluenzaMatthew Rollosson, RN, MPH&TM

Tacoma-Pierce County Health Department2 March 2017

South China Morning Post, February 26, 2017

Influenza Viral infection of the cells that line the respiratory

tract Common symptoms:

◦ Fever◦ Chills, body aches, headache◦ Dry cough, runny nose, sore throat

Not to be confused with “stomach flu”◦ Nausea and vomiting may accompany

influenza, but are not primary symptoms

Treanor, 2015

Influenza Sudden onset Fever usually lasts about 3 days 1 – 2 day incubation Contagious period:

◦ Just before onset of symptoms◦ Virus usually not detected after 5 days

Transmitted by respiratory droplets

Treanor, 2015

Influenza Attack rate: 10% to 20% in unvaccinated

populations◦ As high as 40% to 50%

Average:◦ 3 to 4 days in bed◦ 5 to 6 days restricted activity◦ 3 days school/work lost

Treanor, 2015

Risk factors Increased risk of complications and death from

influenza:◦ Age◦ Chronic heart disease◦ Chronic lung disease◦ Diabetes◦ Immune compromise◦ Obesity◦ Pregnancy/postpartum

Pierce County influenza hospitalizations

40 42 44 46 48 50 52 2 4 6 8 10 12 14 16 18 200

20

40

60

80

100

120

2013-142014-152015-162016-17

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Pierce County influenza deaths

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Decembe

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5

10

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2013-142014-152015-162016-17

Month reported

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Virus Not living cells Must infect cells to replicate

What are H and N? Hemagglutinin: molecule on the surface of

the flu virus that attaches the cells it infects Neuraminidase: molecule on the surface of

the virus that allows newly-made viruses to escape the infected cell

There are 16 H subtypes and 9 N subtypes◦ H17 discovered in Guatemalan bats

Human influenza is usually caused by H1, H2, or H3 and N1 or N2 subtypes

Avian and swine influenza Influenza infects birds and mammals

◦ Economic loss◦ Food insecurity

All 16 hemagglutinin and all 9 neuraminidase subtypes found in birds

Birds and humans have different sialic acid receptors◦ humans are not usually infected with avian

influenzas Pigs have both types of receptors

Antigenic drift

NIH, 2009

CDC/ Douglas Jordan, 2009

Antigenic shift

Reassortment

2009 pandemic H1N1

Garten et al., 2009

2009 pandemic H1N1

Smith et al., 2009

Reassortment

Pandemic influenza Emergence of a novel virus Little or no immunity in the population Higher attack rates Worldwide spread Affects younger adults

◦W-shaped mortality curve

Taubenberger & Morens, 2006; Treanor, 2015

Pandemic influenza 1918 H1N1 “Spanish flu”

◦ 50 to 100 million deaths worldwide 1957 H2N2 “Asian flu”

◦ 1.1 million deaths 1968 H3N2 “Hong Kong flu”

◦ 1 million deaths 1977 reemergence of H1N1 2009 H1N1

◦ 151,700 to 575,400 deaths worldwide

CDC, 2016; Treanor, 2015

2009 H1N1 pandemic March 17, 2009

◦ Mexico: first case March 28 & 30

◦ First two cases in California April 27:

◦ U.S.: 40 laboratory-confirmed cases

◦ Mexico 26 confirmed cases

◦ Canada 6 confirmed cases

CDC, WHO, 2009

2009 H1N1 pandemic April 29, 2009

◦ US: 91 confirmed cases

Half of the U.S. cases were reported from New York City high schools

1 death◦ Austria, Germany, Israel, New Zealand, Spain,

and United Kingdom reporting cases

CDC, WHO, 2009

Laboratory-Confirmed Cases and DeathsMay 21, 2009

WHO, 2009

2009 pandemic H1N1 Worldwide: 80% of deaths were people

under 65 years of age U.S.: 76% of deaths were people between

the ages of 18 and 65 years◦ 9% were people ≥ 65 years of age◦ Pierce County 2016-17: 81% of flu deaths are ≥

65 years of age Pregnant women were 4 times more likely

to be hospitalized than the general population

Dawood et al., 2012; Fowlkes et al., 2011; Jamieson et al., 2009

Pierce County influenza deaths

Median age: 48 yearsYPLL<75: 340

Median age: 79 yearsYPLL<75: 251

Influenza vaccine Interim estimate of 2016-17 influenza vaccine

effectiveness: 48%◦ Risk reduction

CDC, 2017

STAT, February 28, 2017

CDC Influenza Risk Assessment Tool

CDC, 2017

USDA, 2014

References Centers for Disease Control and Prevention. (2016). Past pandemics.

Retreived February 27, 2017 from https://www.cdc.gov/flu/pandemic-resources/basics/past-pandemics.html.

Centers for Disease Control and Prevention. (2017). Interim estimates of 2016-17 seasonal influenza vaccine effectiveness - United States, February 2017. Morbidity and Mortality Weekly Report, 66(6), 167-171.

Dawood, F. S., Iuliano, A. D., Reed, C., Maltzer, M. I., Shay, D. K., Cheng, P-Y., et al. (2012). Estimated global mortality associated with the first 12 months of 2009 pandemic influenza A H1N1 virus circulation: a modeling study. Lancet Infectious Diseases, 12(9), 687-695.

Fowlkes, A. L., Arguin, P., Biggerstaff, M. S., Gindler, J., Blau, D., Jain, S., et al. (2011). Epidemiology of 2009 pandemic influenza A (H1N1) deaths in the United States, April-July 2009. Clinical Infectious Diseases, 52(Supple. 1), S60-S68.

Garten, R. J., Davis, C. T., Russell, C. A., Shu, B., Lindstrom, S., Balish, A., et al. (2009). Antigenic and genetic characteristics of swine-origin 2009 A(H1N1) influenza viruses circulating in humans. Science, 325(5937), doi:10.1126/science.1176225.

References Jamieson, D. J., Honein, M. A., Rasmussen, S. A., Williams, J. L., Swerdlow,

D. L., Biggerstaff, M. S., et al. (2009). H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet, 374(9688), 451-458.

Smith, G. J. D., Vijaykrishna, D., Bahl, J., Lycett, S. J., Worobey, M., Pyrus, O. G., et al., (2009). Origins and evolutionalry genomics of the 2009 swine-origin H1N1 influenza A epidemic. Nature, 459(7250), doi:10.1038/nature08182.

Taubenberger, J. K. & Morens, D. M. (2006). 1918 influenza: the mother of all pandemics. Emerging infectious diseases, 12(1), doi:10.3201/eid1201.050979.

Treanor, J. J. (2015). Influenza (including avian influenza and swine influenza). In G. L. Mandell, J. E. Bennett, & M. J. Blaser (Eds.). Mandell, Douglas, and Bennett's principles and practice of infectious diseases (8th Ed.) [Electronic version].