THURSDAY, Aug. 27, 2009 (HealthDay News) -- As U.S. health officials brace for the expected return of the H1N1 swine flu this fall, much of the focus has been on children and young adults, who seem particularly vulnerable to the newly identified virus.
A federal report released Thursday suggests that focus might be justified. It found that during the period April through July, when swine flu first surfaced in the United States, infection rates in Chicago were highest among children and young adults, especially children 5 to 14 years old who had rates 14 times higher than those seen in adults 60 and older.
The report also found that blacks and Hispanics are somewhat more prone to infection than whites.
The findings reinforce the idea that H1N1 swine flu prevention efforts should target children and young adults. And in keeping with recommendations from the U.S. Advisory Committee on Immunization Practices, younger Americans should be among the first groups inoculated when the swine flu vaccine becomes available this fall, said the study authors, from the U.S. Centers for Disease Control and Prevention.
But health experts said it's important to remember that the swine flu continues to cause only minor illness in most people, including children, and the recovery is fairly quick.
"This is a virus that has consistently, primarily affected young children, teenagers and young adults -- and that has been documented in its course throughout the pandemic, so there's no surprise there," said Dr. Pascal James Imperato, dean of the School of Public Health at SUNY Downstate Medical Center in New York City. "We also know that older adults are less affected by this virus because they have been exposed in the past to ancestral cousins of this H1N1 swine flu virus, and therefore they have some carry-over immunity and protection.
"But the bottom line here is -- and one has to keep emphasizing this -- that the majority of cases of flu caused by this virus have been relatively mild, self-limited and not of great significance," Imperato added, noting that of the seven deaths reported in Chicago, none involved children.
The new CDC review, based on reports to the Chicago Department of Public Health, said there were 1,557 swine flu cases diagnosed in city residents from April through July. The median age of reported confirmed cases was 12 years. The infection rate was highest among children aged 5 to 14 years (147 per 100,000 population), followed by children aged 0 to 4 years (113 per 100,000). Common symptoms were fever and cough, followed by sore throat and shortness of breath, the report said.
Of the 205 laboratory-confirmed patients admitted to a hospital, the median age was 16 years. Hospitalization rates were highest among children aged 0 to 4 years (25 per 100,000), followed by children 5 to 14 years old (11 per 100,000). Hospitalization rates were higher for non-Hispanic blacks (nine per 100,000), Asian/Pacific Islanders (eight per 100,000), and Hispanics (eight per 100,000), compared to non-Hispanic whites (two per 100,000).
The study findings were published in the Aug. 28 issue of the CDC's Morbidity and Mortality Weekly Report.
A second study in the same issue of the journal found that swine flu quickly overtook regular seasonal flu as the predominant strain in New Zealand, which is just emerging from its winter -- and flu -- season.
And, as in North America, the swine flu targeted children and young adults in New Zealand, the study found.
On Wednesday, U.S. health officials echoed Imperato's assessment that the H1N1 swine flu continues to produce mild infections, and has shown no signs of mutating into a more virulent disease as it travels around the globe.
Responding to a White House report released Monday that said a worst-case scenario could lead to infection in half of Americans and as many as 90,000 deaths, Dr. Thomas Frieden, head of the CDC, said, "Everything we've seen in the U.S. and everything we've seen around the world suggests we won't see that kind of number if the virus doesn't change."
Frieden made the comment in a C-SPAN interview taped Wednesday, the Associated Press reported.
The run-of-the-mill regular seasonal flu typically infects up to 20 percent of Americans and causes about 36,000 deaths.
To learn more about swine flu, visit the CDC.