The infection is usually mild, but hospitalization rates are up in recent years.
Hospitalization rates for cat-scratch disease are on the rise, says a new CDC report. The illness—which is sometimes referred to as cat-scratch fever and, yes, is spread by cats—has been around for decades. But in recent years, a higher percentage of patients have developed serious, potentially fatal, complications. Here’s what you need to know, especially if you have young kids or loved ones with weakened immunity.
What is cat-scratch disease?
Cat-scratch disease is a bacterial infection that is transmitted to humans when an infected cat bites or scratches a person badly enough to break the skin, or licks a person’s open wound. The infection is usually mild; the wound can become inflamed and painful, and the person may also develop a fever, headache, loss of appetite, and swollen lymph nodes.
But occasionally, an infection from cat-scratch disease spreads to the brain, eyes, bones, muscles, or heart. This can cause swelling and damage to these organs, and can be fatal if prompt medical attention isn’t received.
The new study, published last week in the journal Emerging Infectious Diseases, looked at health insurance claims pertaining to cat-scratch disease from 2005 to 2013. Over that time, the total number of reported cases declined steadily—from 5.7 cases per 100,000 to 4.0 per 100,000.
But the percentage of people with cat-scratch disease who were hospitalized for the condition actually increased over the study period, from 3.5 percent to 4.2 percent. Based on these results, the study authors estimate that 12,000 people are currently diagnosed with cat-scratch fever each year, and 500 of those are sick enough to be hospitalized.
Why do some people get so sick?
Complications that require hospitalization are rare, but they’re more likely to occur in people with compromised immune systems. That means that anyone who takes immune-suppressing medicines—people with autoimmune disorders like lupus, Crohn’s disease, or rheumatoid arthritis, for example—is at higher risk of becoming seriously ill if infected.
Children age 5 and under are also at higher risk of complications, according to the CDC, since their immune systems aren’t fully developed. Kids are also more likely to be exposed to the bacteria and become infected in the first place: In the study, the majority of patients treated were children ages 5 to 9.
“We think the increased risk is due in part to behavior,” says lead author Christina Nelson, M.D., a pediatrician with the CDC. “Kids are more likely to play with cats and possibly get scratched.”
Nelson says that it’s possible that more people are on immune-suppressing medicines today than in the past, which could be one reason why hospitalizations for cat-scratch disease are up. But it’s also likely that people aren’t actually getting sicker—it’s just that more cases are being diagnosed.
“The medical community has been aware of cat-scratch disease for many years, but these atypical and more severe manifestations are now being identified more often,” Nelson says. “The diagnostics have improved and there may just be better detection today.”
How can you protect yourself (and your cats)?
About 40 percent of cats carry the bacteria responsible for cat-scratch disease, Bartonella henselae, at some point in their lives, according to the CDC, but most show no symptoms. It’s transmitted to them via fleas or fighting with other infected cats. (Dogs can carry and transmit the bacteria, too, says Nelson, but it’s much less common.)
Luckily, Nelson says, you don’t have to give your four-legged friend up for adoption. “We know pets are very important and have many benefits, so we don’t want to send the message that people should avoid cats,” she says. “If you love cats and you have cats, there are some simple prevention methods you can take.”
Giving your cats a monthly flea medication is a good start, she says. (Make sure it’s approved for cats, as some dog-specific formulas aren’t safe for them.) Keep their nails trimmed, and try to limit their time outdoors—or at least try to keep them from hunting or interacting with other animals that may carry the bacteria.
And just in case, don’t let cats lick your wounds, and wash your hands after petting them. If they do draw blood, wash the area well with soap and running water, and call your doctor if you develop any symptoms of infection in the two weeks afterward.
Be extra careful around kittens, as well. Cats younger than 1 year are more likely to carry—and spread—B. henselae bacteria, and are more likely to scratch and bite people while they play and learn.
This is all especially important if you live in the Southern United States, Nelson says: In the study, most cases of cat-scratch fever were in southern states, where fleas are most prevalent, in late summer and early fall.
Worried about giving your furry friend a smooch? There’s no evidence that kissing kittens increases a person’s risk, says Nelson, since the bacteria is known to be transmitted to humans only via open wounds.
“The good news is that cat-scratch disease is mostly preventable,” he says. And by increasing awareness among people who are most at risk—families with small children, people who live in the South, and those with weakened immune systems—she hopes to see fewer cases in the future.