Influenza epidemiology and demographics

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

Epidemiology and Demographics

Age

• Influenza viruses cause disease among persons in all age groups.
• Rates of infection are highest among children, but the risks for complications, hospitalizations, and deaths from influenza are higher among persons aged 65 years and older, young children, and persons of any age who have medical conditions that place them at increased risk for complications from influenza.
• During 1990--1999, estimated average rates of influenza-associated pulmonary and circulatory deaths per 100,000 persons were:

• 0.4-0.6 among persons aged 0-49 years
• 7.5 among persons aged 50-64 years
• 98.3 among persons aged 65 years and older.

National and Regional Summary of Select Surveillance Components

Data cumulative since September 28, 2014 (week 40)

HHS Surveillance Regions	Out-patient ILI†	% positive for flu‡	Number of jurisdictions reporting regional or widespread activity§	2009 H1N1	A (H3)	A(Subtyping not performed)	B	Pediatric Deaths
Nation	Normal	4.8%	1 of 54	7	267	405	392	1
Region 1	Normal	1.6%	0 of 6	0	8	8	4	0
Region 2	Elevated	1.1%	0 of 4	1	17	17	11	0
Region 3	Normal	1.7%	0 of 6	0	16	16	69	0
Region 4	Normal	8.0%	0 of 8	0	56	290	246	1
Region 5	Normal	2.1%	0 of 6	3	28	15	12	0
Region 6	Normal	4.3%	0 of 5	2	32	26	69	0
Region 7	Normal	1.9%	0 of 4	0	12	15	9	0
Region 8	Normal	1.2%	0 of 6	0	15	5	6	0
Region 9	Normal	3.2%	1 of 5	1	27	27	19	0
Region 10	Normal	5.5%	0 of 4	0	56	4	7	0
*HHS regions (Region 1 CT, ME, MA, NH, RI, VT; Region 2: NJ, NY, Puerto Rico, US Virgin Islands; Region 3: DE, DC, MD, PA, VA, WV; Region 4: AL, FL, GA, KY, MS, NC, SC, TN; Region 5: IL, IN, MI, MN, OH, WI; Region 6: AR, LA, NM, OK, TX; Region 7: IA, KS, MO, NE; Region 8: CO, MT, ND, SD, UT, WY; Region 9: AZ, CA, Guam, HI, NV; and Region 10: AK, ID, OR, WA). † Elevated means the % of visits for ILI is at or above the national or region-specific baseline. ‡ National data are for current week; regional data are for the most recent three weeks. § Includes all 50 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands