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Seasonal Influenza Report 2010-11
San Mateo County Health System, Public Health
Week 4 (January 23-29, 2011)
· r Reporting: 650.573.2346 · 650.573.2919 (fax)
Volume 3, Issue 7 (Issued February 8, 2011)
Karen Relucio MD, Assistant Health Officer · Suvas Patel, MPH, Epidemiologist · Scott Morrow MD, MPH, Health Officer
Current Activity
Percentage of Positive Influenza Specimens Weighted by Number of Labs Reporting
San Mateo County, 2009-11
San Mateo County
 Influenza and RSV activity has increased considerably from previous weeks. 2009-10 % Flu Positive
2010-11 % Flu Positive
 Based on lab reports from all seven reporting county and hospital laborato- ries*, there were 41 (19%) influenza positives and 39 (29%) RSV positives within week 4 (Figures 1 and 2). Of the flu positives, 30 were flu A and 11 San Mateo County Public Health Lab (SMC PHL) has the ability to further subtype positive influenza A specimens. During week 4, no specimens were 10%
tested for influenza by RT-PCR at SMC PHL. Influenza-like-illness (ILI) reported from San Mateo Medical Center ED de- 40 4142 43 44 4546 47 4849 50 51 52 1 2 3 4 5 6 7 8 9 10 1112 13 14 1516 17 18 1920 21 2223 24 25 2627 28 29 3031 32 3334 35 36 3738 39
creased slightly from week 3 (1.56%) to week 4 (1.30%), and is greater than activity for the same period last season (Figure 3). ILI visits made up 1.30% of total ED visits in Week 4 and are below the 2009-10 seasonal average of Percentage of Positive Respiratory Syncytial Virus (RSV) Specimens Weighted by Number of Labs
Reporting, San Mateo County, 2009-11
California:

Overall influenza activity in California remains regional. 2009-10 % RSV Positive
2010-11 % RSV Positive
 In Week 4, CDPH received 19 reports of lab-confirmed influenza cases un- der the age of 65 that were admitted to ICU. Four (80%) of the five cases were 2009 H1N1; one case was rapid test positive for influenza A with PCR  The Respiratory Lab Network (RLN) tested 127 specimens for influenza during week 4, of which 60 (47%) were positive for influenza; 24 (40%) were influenza A (H3), 18 (30%) were influenza A (H1N1), 17 (28%) were influ- 4041 4243 4445 46 4748 4950 5152 1 2 3 4 5 6 7 8 9 1011 1213 1415 1617 1819 20 2122 2324 2526 2728 2930 3132 33 3435 3637 3839
Reports of ILI from sentinel providers decreased by 1.2% in week 4 com- pared to the previous week; ILI activity in California remains low.
United States
Proportion of Influenza-like Illness Visits (ILI):
 During week 4 (ending 1/129/11), influenza activity in the United States San Mateo Medical Center ED, 2009-10 and 2010-11 Influenza Seasons
% ILI '09-'10
% ILI '10-'11
Of the 6,209 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating labs, 2,044 (32.9%) were positive for influenza.  Six influenza-associated pediatric deaths were reported: 4 were flu B posi- tive, one was flu A(H3) positive, and 1 was flu A(H1N1) positive. The proportion of outpatient ILI visits was 4%, above the national baseline of San Mateo County Severe and Fatal Influenza Case Surveillance
For the 2010-11 influenza season, California Department of Public Health 40 41 42 43 44 45 46 47 48 49 50 51 52
10 11 12 13 14 15 16 17 18 19 20
has mandated reporting of laboratory confirmed influenza cases requiring CDC Disease Week
intensive care and laboratory confirmed influenza deaths in an effort to moni-tor the circulation of new viruses and characterize populations at risk for TEST OR TREAT?
Influenza and RSV activity is overall is on a seasonal high. Eighty-six Confirmed Influenza
Cumulative
(8%) specimens have tested positive for influenza since the beginning of (1/23/11-1/29/11)
(Weeks 40-4)
flu season in San Mateo County.
 Since influenza is circulating in the community, healthcare provid-
ers should consider empiric treatment in patients with a high
Severe (ICU)
clinical suspicion for influenza.
Fatalities
 Continue to test hospitalized patients with suspected flu for the purposes of infection control and surveillance. Consider empiric treatment in severely ill hospitalized (ICU) cases with suspected Outbreaks
influenza or in patient with progressive illness.  Antivirals used for treatment: Oseltamivir or Zanamivir. So far, *Our reported numbers do not represent all cases of influenza within SMC, but are intended to demonstrate trends in influenza activity Sources: SMC: Kaiser, San Mateo Medical Center, Sequoia Hospital, Peninsula Hospital, San Mateo County Public Health Lab; CA: there is no evidence of resistance to neuraminidase inhibitors California Influenza Surveillance Project: http://www.cdph.ca.gov/programs/vrdl/Pages/CaliforniaInfluenzaSurveillanceProject.aspx ; US: CDC Flu Activity and Surveillance: http://www.cdc.gov/flu/weekly/fluactivity.htm

Source: http://www.llesd.k12.ca.us/Health_InfluenzaFeb2011.pdf