MRSA on the Rise: Infections Have Doubled in 5 Years

Even as in-hospital infections are on the decline, more people are checking into hospitals with the drug-resistant staph infection than those with either HIV or influenza, combined.

Fabrizio Bensch/Reuters

Methicillin-resistant Staphylococcus aureus (MRSA) has rapidly become the bacteria of the decade. MRSA infections now respond only to very advanced antibiotics that were never meant to be a first-line defense. Usually, the drugs have to be delivered intravenously -- which often means spending some nights in the hospital. And it doesn't help that the state of antibiotics is falling behind. With new antibiotics being approved at slower and slower rates, the battle against MRSA has many doctors worrying about creating a superbug they can't kill at all. Now, new data suggest that the MRSA problem may be even worse than we thought.

In a recent study by researchers at the University HealthSystem Consortium (UHC) and University of Chicago Medicine, the rate of MRSA infections recorded at U.S. academic hospitals doubled in the five years between 2003 and 2008. That means nearly 1 in 20 inpatients are now either battling an invasive infection or have been colonized by the bacteria (meaning they carry the germ but don't suffer from any symptoms). In each of the last three years, more MRSA-infected people have checked into the hospital than either HIV-positive or influenza-afflicted patients, combined.

Most of these patients are likely picking up the bacteria even before they reach the hospital grounds. According to a 2010 Centers for Disease Control (CDC) report, infections of invasive MRSA acquired in-hospital fell by 28 percent from 2005 through 2008. Given MRSA's rapid advance in the face of the CDC's finding -- from 21 infections per 1,000 people to 42 per 1,000 -- it's probably safe to conclude that the increases we're seeing can be blamed on community-associated MRSA, a different strain of the germ.

Together, the CDC report and the newer study from the University of Chicago paint two different portraits of the MRSA problem. The first describes the extent of the illness as it actually affects victims today. It only counts serious infections that have penetrated deep into blood or spinal fluid, and makes a point of excluding cases of colonization. The second tries to account for all cases of infection, including colonization, and winds up capturing MRSA's full potential. Knowing how many people have been colonized by MRSA implies just how many are at risk for consequential illness.

In fact, the Chicago scientists say, the new estimate might even be low-balling the disease's pervasiveness because the database they use -- a collection of insurance bills -- tends to under-report instances of MRSA if patients were hospitalized for some other ailment. When the researchers went back to correct for the statistical inaccuracy, they discovered that the insurance claims had missed between a third to one-half of actual MRSA cases as recorded by the hospitals' own records.

At least some of the increase reported in the Chicago paper may simply be due to the fact that we're now more alert to MRSA than we used to be. Better screening means we'll find more of what we're looking for. Still, that doesn't change the fact that more people in general are becoming carriers for MRSA. Getting infected may not guarantee illness in a specific patient, but it also increases the bacteria's chances of eventually being spread to someone who will fall ill from an infection. And that's why understanding the scope of MRSA's potential -- as opposed to measuring only the immediately-consequential cases of MRSA infection -- is so important.