Methicillin-resistant Staphylococcus aureus (MRSA) was responsible for an estimated 94,000 life-threatening infections and 18,650 deaths in 2005, CDC researchers report in the Oct. 17 issue of The Journal of the American Medical Association.
That same year, roughly 16,000 people in the U.S. died from AIDS, according to CDC figures.
The national estimate is more than double the invasive MRSA prevalence reported by CDC researchers five years earlier, says researcher R. Monina Klevens, DDS, MPH.
"MRSA infections are an important public health problem that can no longer be ignored," she tells WebMD. "We need to put this higher on our list of priorities."
Among the highlights from the newly published study:
- While most invasive MRSA infections could be traced to a hospital stay or some other health care exposure, about 15% of invasive infections occurred in people with no known health care risk.
- Two-thirds of the 85% of MRSA infections that could be traced to hospital stays or other health care exposures occurred among people who were no longer hospitalized.
- People over age 65 were four times more likely than the general population to get an MRSA infection. Incidence rates among blacks were twice that of the general population, and rates were lowest among children over the age of 4 and teens.
Known as a superbug because it is resistant to so many antibiotics, MRSA infection is seen most often in patients who have undergone invasive medical procedures or who have weakened immune systems.
Invasive MRSA is a leading cause of potentially life-threatening bloodstream infections, surgical site infections, and pneumonia.
It has been clear for some time that MRSA was a growing problem in the nation's hospitals and other health care settings, but the extent of the problem at the national level has not been well known.
The CDC researchers analyzed 2005 data on invasive MRSA infections from nine sites across the country to arrive at the national prevalence figures.
Based on their findings, they estimated that for every 100,000 people living in the U.S. there were 32 cases of invasive MRSA in 2005.
An estimated 128 cases occurred for every 100,000 people aged 65 and over.
Infectious disease specialist Elizabeth A. Bancroft, MD, tells WebMD that as the U.S. population ages, rates of invasive MRSA are likely to climb even higher unless the nation's hospitals, nursing homes, and other high-risk health care settings take steps to limit its spread.
"Hand washing is one of the most important ways to decrease the spread of MRSA in hospitals, but hand washing compliance rates [among health care professionals] are rarely 100%," she says. "One thing a patient can do to reduce their risk is make sure everyone they come into contact with washes their hands or uses an alcohol hand rub."
The vast majority of MRSA infections occurring outside of the health care setting are noninvasive. These community-acquired infections generally take the form of skin infections and are more easily treated.
In the CDC study, people with what appeared to be community-acquired invasive MRSA infections had better outcomes than those with health care acquired infections, Klevens tells WebMD.
"Most severe infections are health care related, but that is not to trivialize community-associated infections," she says. "The vast majority of community infections are noninvasive, but our study shows that invasive MRSA disease does occur in people without established health care risk factors."