THURSDAY, Oct. 8 (HealthDay News) -- Potentially foreshadowing the U.S. experience this fall and winter, Australian and New Zealand health authorities who have just gone through their flu season report "substantial" traffic in their intensive care units as a result of H1N1 swine flu infections.
Because winter in the Southern Hemisphere takes place during North America's summer, the severity of the flu season Down Under might presage the character of the coming flu season further north.
And a similar report, this time from the U.S. Centers for Disease Control and Prevention, confirms that H1N1-stricken patients cared for in American hospitals during April, May and June were more likely to be pregnant women or younger adults with underlying medical conditions.
Both reports were released online Thursday in the New England Journal of Medicine.
Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said the findings did not surprise him.
"What we've already experienced in the spring and what we're experiencing now is that the [H1N1] virus had a predilection to infect young people and, when you look at people who required hospitalization because of complications, it's disproportionately weighted towards pregnant women and the very young and those with underlying conditions that compromise the immune response," Fauci stated. "It's not surprising. That's exactly the pattern that we've been seeing."
"We're seeing the same kinds of patients," echoed Dr. Tamara R. Kuittinen, an emergency physician with Lenox Hill Hospital in New York City.
So far, that hospital has only seen one confirmed case of H1N1 along with a few suspicious cases, she said.
In the U.S. study, researchers at the CDC examined the medical charts of 272 people hospitalized for H1N1 influenza between April and mid-June of this year. They report that a quarter were admitted to the ICU, and 7 percent died. Nearly three-quarters of patients surveyed had one or more underlying medical conditions such as asthma, diabetes, heart or lung ailments or pregnancy.
Nearly half of patients were children under the age of 18 and just 5 percent were over 65 in keeping with the theory that most elderly Americans may have some immunity to H1N1 due to prior exposure. Elderly patients were also less likely to experience severe illness, the CDC team noted. One positive note: "Patients seemed to benefit from antiviral therapy," the study authors wrote.
In the Australia/New Zealand report, researchers found that from June 1 through Aug. 31, 2009 -- winter in the Southern Hemisphere -- 722 patients with laboratory-confirmed H1N1 infections were admitted to intensive care units (ICUs) in those countries. This translates to 28.7 cases per million residents of the two nations.
Of these, 669 patients were under the age of 65 while 66 were pregnant women, another high-risk group.
Data on 601 patients showed that 172 had a body-mass index above 35, squarely in the obese category. And patients indigenous to both Australia and New Zealand were disproportionately hit.
Taken together, patients admitted to an ICU stayed there for a total of 8,815 "bed days," or 350 per million inhabitants. The average stay was seven days, ranging from 2.7 to 13.4 days.
Almost two-thirds of those hospitalized with the flu needed mechanical ventilation, and the average time spent on ventilation was eight days.
H1N1 patients took up a maximum of 7.4 beds per million inhabitants in a day in two countries that have 75 ICU beds for each million residents.
According to the report, "the greatest effect on ICU resources in a given region occurs approximately four to six weeks after the first confirmed winter ICU admission and ... the extra workload lasts several weeks."
As of Sept. 7, 103 of the 722 Australian/New Zealand patients -- or just over 14 percent -- had died, while 15.8 percent were still in the hospital.
Even though that seems like a high death rate, Kuittinen pointed out that these patients were typically very sick before catching the flu and probably had multiple other health problems.
And the mortality rate was no higher than that typically seen with seasonal flu, stressed the authors of the report, from several different universities in Australia.
Another expert said the findings were in line with expectations.
"It verifies a lot of our planning notions for the past couple of years. We're seeing a lot of the same numbers, it's reassurance," said Dr. Michael Proctor, director of training at Texas A&M Health Science Center School of Rural Public Health and the National Center for Emergency Medical Preparedness and Response, in College Station, Texas.
"There's no cause for panic, just cause for caution," Kuittinen added. "Look at this, hear this news and practice good hygiene. Wash your hands, carry hand sanitizers, sneeze into a tissue."
Learn more about H1N1 flu from the U.S. Centers for Disease Control and Prevention.
SOURCES: Tamara R. Kuittinen, M.D. emergency physician, Lenox Hill Hospital, New York City; Anthony Fauci, M.D., director, U.S. National Institute of Allergy and Infectious Diseases, Bethesda, Md.; Michael Proctor, M.D., director of training at Texas A&M Health Science Center School of Rural Public Health and the National Center for Emergency Medical Preparedness and Response; College Station, Tex; Oct. 8, 2009, New England Journal of Medicine, online