The national reporting period for influenza begins in early fall and continues through late May. Preliminary data from national influenza surveillance systems indicated that the 2003-2004 season was more severe than the previous three seasons but was within the range expected for a typical A (H3N2) season.
The 2003-2004 Texas influenza season started when influenza A H3 was first identified by the Texas Department of State Health Services Virology Lab from a specimen collected September 29, 2003, in Travis County. The Texas Children’s Hospital in Houston also identified influenza A H3 that same week. Outbreaks of influenza-like illness were occurring in school-aged children in the Houston area early October. DSHS received reports of school campus/district closures from 4 counties.
By mid-October, and again in November, statewide health advisories were issued reporting heavier than usual influenza activity and urging people to get a flu vaccination. Reports from Texas and other states indicated the possibility of higher than usual levels of severe morbidity and fatalities from flu-related complications in high-risk pediatric and other populations; and the Centers for Disease Control and Prevention requested that state and local health departments report influenza-associated deaths in persons aged <18 years. In an unprecedented period of heightened demand, injectable flu vaccine became unavailable as supplies were exhausted by mid to late December. FluMist, a recently licensed nasal aerosol vaccine, remained available.
The state influenza activity level was widespread (the highest level) for 13 consecutive weeks from mid-October to mid-January. Influenza activity peaked in late November. The flu activity level continued sporadically through the week ending 3/27/04, and then was reported as "no activity" for the rest of the season, through the week ending 5/22/04.
The flu vaccine composition for 2003-2004 included: A/New Caledonia H1N1, A/Panama H3N2, and B/Hong Kong. One of the issues associated with this flu season was the difference in the primary circulating strain of influenza compared to the vaccine strain. The primary circulating strain of the season was A/Fujian H3N2. The vaccine strain, A/Panama H3N2, did not provide optimal protection from the circulating (related, but genetically different) Fujian strain. However, the vaccine offered more protection than no vaccination at all.
The last influenza A culture received by DSHS was collected 2/12/04 in Bell County. The one influenza B specimen received by DSHS, was collected 3/4/04, in Wichita County. It was identified as B/Sichuan.
As of 5/22/04, the DSHS virology lab has received 1,684 respiratory specimens. 884 of those (53%) were positive for influenza A H3 and one specimen was positive for influenza B. Like other state virology laboratories in the country, DSHS periodically submits early, mid, and late-season, as well as unusual isolates, to the CDC for strain characterization. Of the 72 isolates submitted: 8 were identified as A/Panama/2007/99-like (H3N2), 58 were identified as A/Korea/770/2202-like (H3N2), (a Fujian-like strain), 2 were identified as A/Fujian/411/2002 (H3N2), 1 was identified as B/Shanghai/361/2002-like, 2 were negative, and 1 was pending.