AUSTIN, Texas - An outbreak of invasive group A streptococcal infections (GAS) in Texas is responsible for as many as 170 illnesses and 36 deaths, according to the latest report from Texas Department of Health (TDH).
Since Dec. 1, 1997, 109 adults and 54 children have become ill and nine children have died. Sixteen children had a primary infection with varicella, according to preliminary results of the TDH investigation.
"Approximately one-third of children in the outbreak had a recent infection with varicella," said Benjamin Schwartz, MD, medical epidemiologist with the National Center for Infectious Diseases at the Centers for Disease Control and Prevention (CDC). Chickenpox not only weakens a child's immune system, but the lesions often covering the child's body provide an open invitation for the bacteria.
Until this year, Texas annually reported between 80 and 100 cases of GAS infections during an entire year. However, public health officials believe invasive GAS infections have been underreported in previous years. Officials also said the historical data is not extremely reliable because GAS has only been a reportable condition since 1994, said Doug McBride, TDH spokesman.
The CDC estimates an average of 1.5 to 3.3 cases per 100,000 people occur each year.
The majority of cases occurred between Dec. 1, 1997, and March 1. Thirty-nine cases were reported in December; during January and February 51 cases were reported each month; and 29 were reported in March. Onset of the last case was reported March 27.
The ages of the reported cases range from infants (eight cases under 1 year) to 92 years, but the majority of cases were under the age of 60. Although not a significant amount, a higher percentage of cases were reported among men than women, said Beverly Ray, RN, an epidemiologist with the TDH infectious diseases and surveillance division.
"We currently don't have any theories for why more cases occurred in men than women," she said.
No link is confirmed between any of the 170 identified cases, but the investigation is ongoing. McBride said transmission may have occurred between two sets of siblings, but the division is currently reviewing medical records for the cases. "We're still investigating, but I doubt there is a link," she said.
All outbreak cases were culture-positive for group A streptococci but official causes of death for the majority of cases included streptococcal toxic shock syndrome, pneumonia and necrotizing fasciitis. Results were incomplete at press time as to the number of deaths attributed to each condition.
Most of the cases occurred in Harris County (which includes the city of Houston), which reported 56 cases. Travis County (including Austin) reported 22 and Bexar County (including San Antonio) reported 12.
"The number of cases now seem to be tapering off," according to McBride.
The Texas outbreak follows a smaller outbreak that occurred in mid-February in Illinois which affected mostly elderly people; this outbreak had a high case-fatality rate. Albuquerque also had a significant number of cases, Schwartz said.
The increase in cases seen over the recent years is most likely because of enhanced surveillance put into place during the late 1980s, Schwartz said. Data does not show an increase in overall cases, but possibly an increase in severe cases.
"It's hard to tell whether there has been a change in the rate of infection overall in the United States," Schwartz said. "In other countries, there have been outbreaks that have lasted one or more years."
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