WASHINGTON — It's nature's stealth killer. It's not always the medical examiner's prime suspect. And the deadly toll it exacts often becomes clear only well after it has left the scene.
Stifling heat has already claimed at least several lives in the mid-Atlantic region this summer. Those numbers are likely to grow, experts said, because hot weather's casualty figures are generally counted days and weeks after a heat wave ends.
One person in Kansas has died from the heat so far this summer, according to the Kansas Department of Health and Environment: a 48-year-old man in the north-central part of the state. Officials would not release more details.
High temperatures claim more lives in the United States than tornadoes, hurricanes, floods and
lightning combined — about 700 a year, according to official estimates.
Almost all are preventable. Better understanding can help prevent more deaths, some officials say, by encouraging people to take measures such as drinking fluids and seeking relief in an air-conditioned building, even if for just a few hours a day.
"People don't realize the severity of heat on health," said George Luber, an expert on heat at the Centers for Disease Control and Prevention.
A judgment call
It will be a while before the summer's true tally is apparent, experts said. That's not just because more hot weeks are likely yet to come.
Figuring out whether high temperatures played a role in a death is a complicated process. Different jurisdictions use different criteria, and what might be listed as a heat-related death in one state could be considered a heart attack in another.
The decision is ultimately a judgment call by doctors and medical examiners that may take weeks.
As a result, experts say, a heat wave's casualty figures are often underreported.
"The current numbers are likely underestimating the true magnitude of mortality," Luber said.
During heat waves, many more people than usual die of such illnesses as chronic respiratory ailments and heart disease, Luber said.
Clear-cut cases of hyperthermia death are relatively rare, in part because the finding depends on hospital or emergency personnel measuring an elevated body temperature, usually 105 degrees or higher, at the time of death or immediately after.
There are "a lot of gray zones," said Randy Hanzlick, acting vice president of the National Association of Medical Examiners and chief medical examiner of Fulton County, Ga.
"If someone has really severe heart disease and it's really hot and they were working outside gardening, and they pass away, is that heat-related? That becomes a total judgment call," said Bart Ostro, chief of the air pollution epidemiology section at California's Environmental Protection Agency, who has studied heat-related mortality.
The KDHE does not systematically collect data on heat deaths, said Katie Ingels, a public information officer for the agency.
"We are working with our partners on how to collect this data so that it will be available in the future," Ingels said.
Wichita heat warnings
The Wichita office of the National Weather Service made changes in its heat warning criteria for the metropolitan area after numerous heat-related hospital admissions occurred during an extended hot spell in July 2006, said Dick Elder, meteorologist-in-charge at the branch.
Before then, heat warnings would be issued if the heat index — a measure of what it feels like outside — reached 110 degrees and the overnight low temperature did not fall below 80.
The temperature topped 105 for five straight days in mid-July that year, but never reached 110 and always fell below 80 — so heat warnings were never issued.
"People were succumbing to the hot weather during the day, and the question was being asked, 'Why don't we have any heat warnings out?' " Elder said.
The agency has since dropped the low temperature limit and now issues a heat warning if the heat index hits 110 degrees on one day or at least 105 on three straight days.
The CDC's most recent analysis of heat-related deaths in the United States, from 1999 to 2003, found that including deaths in which heat was a contributing factor increased the number from 2,238 to 3,442, or 54 percent.
The experience of such cities as Philadelphia and Chicago during the mid-1990s brought widespread attention to the way heat deaths were defined. Until then, medical examiners typically relied on the classic definition of hyperthermia death, relying on elevated core body temperatures, officials said.
But in many suspected cases of hyperthermia death, people were alone, leaving no clue as to their body temperatures when they died.
Medical examiners in the two cities began looking for other clues, such as whether windows were closed and the absence of fans or air conditioners.
As a result, during Philadelphia's heat wave in 1993, 118 residents were reported to have died of heat-related causes, while such nearby cities as New York, Washington and Baltimore, which used the old criteria, reported few such deaths or none.
During Chicago's heat wave in July 1995, the heat index topped 100 degrees for five days and surpassed 115 degrees on two consecutive days, according to official reports. The medical examiner's office reported more than 700 deaths.
The high death counts were controversial, but the CDC subsequently confirmed the findings.