IDCU HomeInfectious Diseases A-CD-GH-LM-QR-ST-ZIDCU Health TopicsDisease ReportingRelated Rules & RegulationsImmunization BranchAbout IDCURelated DSHS SitesStaff Contact List
  • Loading...
    Contact Us

    Infectious Disease Control Unit
    Mail Code: 1960
    PO BOX 149347 - Austin, TX 78714-9347
    1100 West 49th Street, Suite T801
    Austin, TX 78714

    Phone: 512 776 7676
    Fax: (512) 776-7616


    E-mail

2011 - 2012 Texas Influenza Surveillance Information

Loading...

Influenza

Influenza
(Flu)
ICD-9 487; ICD-10 J10,11
Related Topics: Protecting Yourself During the Cold and Flu Season, Avian Flu, Vaccine Preventable Diseases, Asthma and SARS
Texas Influenza Summary Report, 2011–2012 Season (October 2, 2011 – September 29, 2012)

Overview
The 2011–2012 season was classified as mild both for the US and Texas. During the 2011–12 influenza season, Texas and US ILINet data indicated that the peak percentage of visits due to ILI and the number of weeks above baseline were much lower compared to the 2010–2011 season1,2. US data indicated that hospitalization rates in persons of all ages were lower compared to the 2010–11 season; there were also fewer influenza-associated pediatric deaths. Although influenza A (H3N2) viruses predominated in the US, the predominant virus detected in Texas was 2009 influenza A (H1N1) (referred to as influenza A (H1N1) hereafter).

Viral Surveillance
National Respiratory and Enteric Virus Surveillance System (NREVSS)[i]
During the 2011–12 season, 28 participating laboratories in most Texas Health Service Regions (HSRs) submitted data to NREVSS on antigen detection, virus isolation (i.e., cultures), and polymerase chain reaction (PCR) testing for influenza. Of the 63,384 influenza tests that were reported to NREVSS from Texas laboratories, 3,270 (5.2%) were positive for influenza virus. Of the 3,270 positive tests, 2,632 (80.5%) tests were positive for influenza A and 638 (19.5%) tests were positive for influenza B. The majority (83.7%) of the positive test results for influenza A reported through NREVSS were reported as influenza A (not subtyped) because most laboratories in Texas do not perform subtyping. Of the 430 influenza A results for which subtyping was reported, 78.5% were identified as influenza A (H1N1) and 21.4% were identified as influenza A (H3N2). The peak of influenza activity reported by Texas NREVSS laboratories occurred during the week ending March 17, 2012 (MMWR week 11), when 16.5% of tests were positive for influenza virus (Figure 1).

Figure 1.  Influenza types and subtypes reported by National Respiratory and Enteric Virus Surveillance System laboratories in Texas, 2011–12 season
NREVSS Graph

Texas Public Health Laboratories[ii]
The first PCR positive influenza specimen of the season was collected on October 16, 2011 (MMWR week 42) from Travis County and identified as influenza A (H3N2) by the DSHS Austin Lab (Figure 2). After the initial positive result, no more positive influenza specimens were detected until the week ending December 17, 2011 (MMWR week 50). The first specimens positive for influenza A (H1N1) and influenza B were collected during the week ending January 7, 2012 (week 1). All three virus types and subtypes circulated throughout the remainder of the season; however, influenza A (H1N1) was the predominant subtype of influenza A that was detected during the 2011–12 season in Texas. The proportion of specimens positive for influenza B began increasing in the week ending April 7, 2012 (week 14).

Figure 2.  Influenza types and subtypes identified by Texas public health laboratories, 2011–12 season
Flu Types
Submission of specimens for influenza surveillance began to increase during the week ending February 4, 2012 (week 5). The largest number of specimens collected for influenza surveillance, 181, occurred during the week ending March 10, 2012 (week 10); the peak percentage of specimens positive for influenza, 80.3%, occurred during the week ending March 17, 2012 (week 11). The proportion of specimens positive for influenza virus in the 2011–12 season equaled or exceeded 10% for 25 consecutive weeks. Specimen submission began to decline sharply beginning in the week ending April 7, 2012 (week 14).

Over the course of the 2011–12 influenza season, Texas public health laboratories received 2,352 specimens for influenza surveillance that met specimen testing and handling requirements; of those, 843 (35.8%) were positive for influenza virus. Of those that were positive for influenza virus, 673 (79.8%) were identified as influenza A viruses and 170 (20.2%) were identified as influenza B viruses. All influenza A positives were subtyped: 485 (72.1%) were identified as influenza A (H1N1) and 188 (27.9%) were identified as influenza A (H3N2).

 

Antigenic Characterization of DSHS Austin Laboratory Influenza Positives[iii]
Forty-four influenza viruses from Texas were submitted for antigenic characterization during the 2011–12 season: 16 influenza A (H1N1) viruses, 12 influenza A (H3N2) viruses, and 15 influenza B viruses.

Fifteen of the influenza A (H1N1) viruses were characterized as A/California/07/2009 (H1N1)-like, the 2011–12 Northern Hemisphere vaccine influenza A (H1N1) component; the remaining influenza A (H1N1) virus could not be grown in culture. Of the 12 influenza A (H3N2) viruses, eight (66.7%) were characterized as A/Perth/16/2009-like (H3N2), the 2011–12 Northern Hemisphere influenza A (H3N2) vaccine component; the remaining four influenza A (H3N2) viruses showed reduced titers to A/Perth/16/2009 (H3N2).

Of the 15 influenza B viruses characterized, seven (46.7%) were characterized as B/Brisbane/60/2008-like (part of the Victoria lineage), the 2011–12 Northern Hemisphere vaccine influenza B component. Eight (53.3%) viruses were characterized as similar to B/Wisconsin/01/2010 (a Yamagata lineage virus). Both lineages were detected throughout the spring and early summer months of 2012. Antigenic characterization results from Texas specimens were similar to those reported by the Centers for Disease Control and Prevention (CDC) during the 2011–12 season in the United States2.

Antiviral Resistance Testing of DSHS Austin Laboratory Influenza Positives
During the 2011–12 season, thirteen influenza A (H1N1) isolates tested were identified as positive for the mutation that confers resistance to oseltamivir. Two specimens were identified as having the mutation through diagnostic testing at CDC and were related to patient treatment with antivirals.

Nine (81.8%) of the remaining eleven specimens were collected from residents of HSR 11; the other two were from residents of HSR 2/3. Patient onset dates ranged from January 18, 2012 to March 25, 2012. The patients ranged in age from 2 months to 28 years (median: 5 years). No epidemiological links were found among the cases. Five (45.5%) hospitalizations and no deaths occurred. Six (54.5%) cases—including four of those hospitalized—had significant underlying medical conditions. Although nine (81.8%) of the eleven cases reported treatment with oseltamivir, specimens that tested positive for the antiviral resistant influenza A (H1N1) virus were collected from eight (72.7%) of the eleven patients before the patients started antiviral therapy. However, one of these patients reported being exposed prior to illness onset to an ill relative who was being treated with antivirals.

Morbidity Surveillance
US Outpatient Influenza-like Illness Surveillance Network (ILINet)
[iv]

Eighty-six providers in Texas submitted data to ILINet for at least one week during the 2011–12 season (i.e., 2011 MMWR week 40 to 2012 week 39) (Figure 3). During the official influenza reporting season (i.e., 2011 week 40 to 2012 week 20), an average of 66 providers submitted data on an average of 25,385 patient visits each week.

The US Health and Human Services (HHS) Surveillance Region 6[v] ILI baseline calculated by CDC was 4.3% for the 2011–12 influenza season. The Texas baseline for the 2011–12 season was 5.87%.[vi] According to data from Texas ILINet participants, the percentage of visits due to ILI first exceeded the HHS Region 6 baseline during the week ending February 25, 2012 (MMWR week 8), with 5.18% of visits due to ILI (Figure 4). Influenza-like illness peaked during the week ending March 17, 2012 (week 11). During that week, ILINet providers reported that influenza-like illness accounted for 5.37% of all patient visits. The percentage of visits due to ILI fell below the regional baseline in the week ending March 24, 2012 (week 12). The percentage of visits due to ILI continued to decrease and remained below the regional baseline for the remainder of the season.

Overall, ILI activity in Texas exceeded the HHS Region 6 baseline for four consecutive weeks. The percentage of visits due to ILI did not exceed the Texas baseline during the 2011–12 season. The peak percentage of ILI reported in Texas ILINet for the 2011–12 season was the lowest peak reported since the 2002–2003 influenza season.

Figure 3.  Number of active Texas participants per county in the US Outpatient Influenza-like Illness Surveillance Network, 2011–12 influenza season[vii]
FluMap

Figure 4.  Percentage of visits for influenza-like illness reported by the US Outpatient Influenza-like Illness Surveillance Network in Texas, 2011–12 season

IliOutpatientGraph

Influenza Incidence Surveillance Project (IISP)[viii]
From July 31, 2011 through July 28, 2012, six Texas providers reported a total of 26,734 patient visits for any reason and 395 patient visits for influenza-like illness (ILI), or 1.48% of visits for ILI during the project period. Over the entire project period, the percentage of visits for ILI was highest at 4.42% for 2- to 4-year-old children. The percentage of visits for ILI was lowest for adults aged 65 years and older at 0.38%. During influenza surveillance season, the estimated incidence of ILI in outpatient healthcare populations peaked at 315.59 per 100,000 population (week ending February 4, 2012). The percentage of visits for ILI peaked at 4.08% in the week ending February 4, 2012 (MMWR week 5) (Figure 5).

A total of 215 ILI specimens were submitted for testing during the project period, and 209 (97.2%) of those were acceptable for testing. Overall, 105 (50.2%) ILI specimens tested for the IISP project were positive for at least one respiratory virus and 13.4% of all specimens tested were positive for an influenza virus (includes single and mixed infections). Results are displayed in Table 1.

Providers began submitting specimens for IISP in late August 2011. Rhinoviruses and parainfluenza viruses were the main respiratory viruses detected from September 2011 through December 2011 (Figure 6). Influenza viruses, human metapneumoviruses, and respiratory syncytial viruses were detected from January 2012 through mid-March 2012. Very few patient specimens were submitted from April 2012 through July 2012; during these weeks fewer than 10 patients with ILI were seen each week by all providers in the IISP project combined.

Figure 5.  Percentage of visits for influenza-like illness reported by providers in the Influenza Incidence Surveillance Project, Texas, 2011–12 season
Ili Percentage Graph

Table 1. Number and percentage of respiratory viruses detected through the Influenza Incidence Surveillance Project, Texas, 2011–12 season

Viruses detected

Number of specimens positive

Percentage of total specimens positive

Positive for one or more respiratory viruses

105

50.24%

Influenza virus (all types/subtypes)

25

23.81%

Influenza A (not subtyped)

2

8.00%

Influenza A (H1N1)

18

72.00%

Influenza A (H3N2)

4

16.00%

Influenza B

1

4.00%

Adenovirus

1

0.95%

Human metapneumovirus (HMPV)

8

7.62%

Parainfluenza virus 1

13

12.38%

Respiratory syncytial viruses (RSV)

5

4.76%

RSV A

4

80.00%

RSV B

1

20.00%

Rhinovirus

47

44.76%

Multiple viruses detected

6

5.71%

Rhinovirus and parainfluenza virus 1

3

50.00%

Rhinovirus and influenza A (H1N1)

2

33.33%

Influenza A (H3N2) and HMPV

1

16.67%

Negative or inconclusive

104

49.76%

Total tested

209

100.00%

Figure 6.  Respiratory viruses detected through the Influenza Incidence Surveillance Project (IISP), Texas, 2011–12
IISP Count Chart

School Closures and Institutional Outbreaks
No school outbreaks were reported during the 2011–12 season. One outbreak of influenza B occurred in a daycare in HSR 9/10 in the first two weeks of June 2012.

Two institutional outbreaks were reported in a correctional facility and an assisted living facility in HSRs 7 and 9/10. The correctional facility reported ILI and one positive influenza test in a cohort of inmates during weeks 3 (week ending January 21, 2012) and 4 (week ending January 28, 2012). The assisted living facility reported influenza A (not subtyped) illnesses in residents and staff beginning in week 10 (March 10, 2012).

Mortality Surveillance
Influenza-Associated Pediatric Mortality
[i]

Four influenza-associated pediatric fatalities were reported to DSHS during the 2011–12 influenza season. The reported deaths occurred during the week ending January 21, 2012 (MMWR week 3) through the week ending March 10, 2010 (week 10). These four deaths were reported in residents of HSRs 1, 2/3, 7, and 8. All patients had confirmed influenza A infections. Only one influenza virus was subtyped, and this was identified as influenza A (H1N1).

The median age at death was 9 years with patients ranging in age from 3 months to 13 years. Of the four reported cases, one patient was younger than 6 months of age, two patients were 5–10 years of age, and one patient was 11–17 years of age. Of the three children for whom influenza vaccination status was known, none were vaccinated for the current season (one was too young to receive the vaccination). Three (75%) of the four patients had significant underlying medical conditions and/or a bacterial co-infection.

Texas Influenza Surveillance System
Background
Influenza and influenza-like illnesses (ILI) were last reportable by law in any county in Texas in 19936. During that year, over 275,000 cases of influenza and influenza-like illness were reported to the Texas Department of State Health Services (DSHS) (legacy agency Texas Department of Health). The only influenza categories reportable by law in Texas for the 2011–12 season included influenza-associated pediatric fatalities, outbreaks associated with influenza, and novel influenza A infections in humans (reportable as an exotic disease). Because there is no current reporting requirement for the majority of influenza illnesses, it is unclear how many influenza-related illnesses, hospitalizations, and deaths occur each year in Texas residents. A small number of influenza cases are reported voluntarily through sentinel surveillance networks composed of laboratories, hospitals, physicians, nurses, schools, and universities located throughout the state. Additional resources include web-based influenza and ILI reporting systems, as well as local and regional health departments that gather data from surveillance participants in their jurisdictions. Data from all sources are reported to the DSHS Central Office in Austin, compiled, and presented weekly in the Texas Influenza Surveillance Report.

Components
The national influenza reporting period begins in early October [Morbidity and Mortality Weekly Report (MMWR) week 40] and continues through late May (MMWR week 20). Influenza surveillance in Texas continues year-round, although in reduced capacity during the summer months. The goals of influenza surveillance are to determine when and where influenza viruses are circulating, if the circulating viruses match the vaccine strains, what changes are occurring in the viruses, what impact influenza is having on hospitalizations and deaths, and the severity of influenza activity. The three main Texas influenza surveillance components are viral, morbidity, and mortality surveillance. Viral influenza surveillance at the state level consists of influenza test results reported by Texas laboratories in the National Respiratory and Enteric Virus Surveillance System (NREVSS) and specimens sent to public health laboratories for influenza surveillance testing. Morbidity surveillance consists of reports of novel influenza A virus infections in humans; reports of ILI from Texas participants in the US Outpatient Influenza-like Illness Surveillance Network (ILINet), the Influenza Incidence Surveillance Project (IISP), and local and regional health department surveillance; and reports of influenza or ILI outbreaks. Mortality surveillance includes influenza-associated deaths in children fewer than 18 years of age.


References

  1. Centers for Disease Control and Prevention. 2010–2011 Influenza Season Summary. Available at http://www.cdc.gov/flu/weekly/weeklyarchives2010-2011/10-11summary.htm.  Accessed on February 6, 2013.
  2. Centers for Disease Control and Prevention. FluView: 2011-2012 Influenza Season Week 20 ending May 19, 2012. Available at http://www.cdc.gov/flu/weekly/weeklyarchives2011-2012/weekly20.htm. Accessed on February 6, 2013.  
  3. Centers for Disease Control and Prevention. U.S. Outpatient Influenza-like Illness Surveillance Network: 2010–11 Workfolder. 55.20E, Rev. 06/2011.
  4. Council of State and Territorial Epidemiologists. Influenza Incidence Surveillance Project – Application. April 1, 2011.
  5. Centers for Disease Control and Prevention. Influenza-Associated Pediatric Mortality, 2004 case definition. Available at: http://wwwn.cdc.gov/NNDSS/script/casedef.aspx?CondYrID=729&DatePub=1/1/2004%2012:00:00%20AM.   Accessed on February 6, 2013.
  6. Texas Department of Health. Epidemiology in Texas 1993 Annual Report. Available at: http://www.dshs.state.tx.us/idcu/data/documents/1993%20Texas%20Annual%20Report.pdf.



[i] NREVSS is an online laboratory results reporting system for several respiratory and enteric viruses that is maintained by the CDC. NREVSS reporters in Texas are primarily hospital laboratories, although two public health laboratories (Tarrant County Public Health [Laboratory Response Network] Lab and the DSHS Austin Laboratory) also participate. See http://www.cdc.gov/surveillance/nrevss/ for more information.

 [ii] Influenza surveillance specimens are submitted for PCR testing to the DSHS Austin laboratory, the Houston Department of Health and Human Services Laboratory, and the Texas Laboratory Response Network (LRN) laboratories throughout the season by physicians, hospitals, clinics, and health departments across Texas. The Texas LRN laboratories have been participating in influenza surveillance since the 2008–2009 influenza season; the participating LRN laboratories are located in Corpus Christi, Dallas, El Paso, Fort Worth, Harlingen, Houston, Lubbock, San Antonio, and Tyler.

[iii] Like other state virology laboratories in the country, DSHS submits early, mid, and late-season as well as unusual influenza viruses to the CDC for strain characterization. Specimens and influenza viruses are also submitted at regular intervals according to CDC’s instructions.

[iv] Texas participants in ILINet report weekly on the number of patient visits for ILI by age group and the total number of patients seen for any reason. For ILINet reporting, ILI is defined as “fever (≥100°F [37.8°C], oral or equivalent) and cough and/or sore throat in the absence of a known cause other than influenza”3. ILINet data are used to calculate a weekly percentage of visits due to ILI.

[v] HHS Surveillance Region 6 includes Arkansas, Louisiana, New Mexico, Oklahoma, and Texas. [vi] The baseline is the mean percentage of patient visits for ILI during non-influenza weeks for the previous three seasons plus two standard deviations. Baselines are calculated for official influenza reporting season only (i.e., MMWR weeks 40 through 20). A “non-influenza week” is defined as a week in which less than 10% of specimens tested positive for influenza.

[vi] The baseline is the mean percentage of patient visits for ILI during non-influenza weeks for the previous three seasons plus two standard deviations. Baselines are calculated for official influenza reporting season only (i.e., MMWR weeks 40 through 20). A “non-influenza week” is defined as a week in which less than 10% of specimens tested positive for influenza.

[vii] In order to be considered an active participant in ILINet, a provider must report at least one week during the season. Therefore, active providers did not necessarily report every week of the influenza reporting season.

[viii] IISP is a collaborative project among CDC, the Council of State and Territorial Epidemiologists (CSTE), and state and local health departments to “[monitor] the age-specific incidence of medically-attended ILI and influenza-associated ILI in real time throughout the influenza season”4. Providers submit weekly data on the number of patients with ILI by age group and the total patients seen by age group. Specimens collected from the first 10 ILI patients seen each week by each participating provider are tested for the presence of influenza and other respiratory viruses (adenovirus, rhinovirus, respiratory syncytial virus, human metapneumovirus, and parainfluenza virus). Texas participated in IISP for the first time during the 2011–12 season.

[ix]An influenza-associated death is defined for surveillance purposes as a death resulting from a clinically compatible illness that was confirmed to be influenza by an appropriate laboratory or rapid diagnostic test. There should be no period of complete recovery between the illness and death. Influenza-associated deaths in all persons aged <18 years should be reported”5.


2011 - 2012 Texas Influenza Surveillance Information --- Flu Reports

For the week ending: 10/08/11; 10/15/11; 10/22/11; 10/29/11; 11/05/11; 11/12/11;
11/17/11; 11/24/11; 12/03/11; 12/11/11; 12/18/11; 12/25/11; 12/31/11; 1/7/12;
1/14/12; 1/21/12; 1/28/12;  2/4/12; 2/11/12; 2/18/122/25/12; 3/3/12; 3/10/12;
3/17/12; 3/24/12; 3/31/12; 4/7/12; 4/14/12; 4/21/12; 4/28/12; 5/5/12; 5/12/12;
5/19/12; 5/26/12; 6/2/12; 6/9/12; 6/16/12; 6/23/12; 6/30/12; 7/7/12; 7/14/12;
7/21/12; 7/28/12; 8/4/12; 8/11/12; 8/18/12; 8/25/12; 9/1/12; 9/8/12; 9/15/12;
9/22/12; 9/29/12;

Return to the Top of the Page

  • Loading...
Last updated April 04, 2013