A staph infection is any infection caused by Staphylococcus aureus, a type of bacteria that naturally lives on human skin and inside the nose. Most of the time, these bacteria cause no problems at all. Roughly 20% to 30% of people carry staph persistently, and another 30% carry it on and off, without ever getting sick. Infection happens when the bacteria enter the body through a break in the skin, a surgical site, or a medical device, triggering symptoms that range from a minor skin bump to a life-threatening bloodstream infection.
Where Staph Bacteria Live
Staph bacteria colonize several areas of the body, most commonly the inside of the nostrils, the throat, the armpits, the groin, and the skin surface. They can also live in the intestinal tract. In healthy people, these bacteria coexist peacefully with the body’s immune defenses. The trouble starts when the skin barrier is broken, whether by a cut, a scrape, a surgical incision, or even a hair follicle irritated by shaving. Once bacteria slip past that barrier, the immune system may not contain them quickly enough, and infection takes hold.
What Staph Infections Look and Feel Like
The vast majority of staph infections affect the skin. They tend to show up in a few recognizable forms:
- Folliculitis: Small, pus-filled bumps around hair follicles that resemble pimples. They’re typically itchy and can develop into crusty sores.
- Boils (furuncles): Deeper pockets of pus that form under the skin, commonly under the arms, around the groin, or on the buttocks. They’re painful, red, and swollen.
- Carbuncles: Clusters of connected boils, often appearing on the back of the neck. These tend to be more severe and can cause fever.
- Impetigo: Sores, usually on the face, that burst open and leave behind a distinctive honey-yellow crust. This form is especially common in young children.
All of these typically start with redness, warmth, and swelling in one spot. Pain ranges from mild tenderness with folliculitis to throbbing discomfort with a deep boil. Many people first notice what looks like a spider bite or a stubborn pimple that keeps getting worse instead of better.
How Staph Spreads
Staph passes from person to person through direct skin contact, which is why it spreads readily in households, locker rooms, and athletic settings. Sharing towels, razors, or washcloths is a well-documented risk factor. Many people who develop a community staph infection were never colonized themselves beforehand, meaning they picked up the bacteria from someone else shortly before getting sick.
Contaminated surfaces also play a role. Staph bacteria can survive on objects like countertops, gym equipment, and bedding for months under the right conditions. Research on household transmission found that having staph contamination on shared surfaces significantly increased the odds of recurrent infections among family members.
Who Is Most at Risk
Anyone can get a staph infection, but certain factors raise the odds considerably. People with chronic conditions like diabetes, cancer, or vascular disease face higher risk because their immune defenses or skin integrity may be compromised. Injection drug use is another major risk factor in the community setting.
In hospitals, the risk climbs for patients in intensive care units, those recovering from surgery, and anyone with an indwelling medical device such as a catheter, joint replacement, or cardiac implant. These devices give bacteria a surface to cling to and a direct path past the skin’s protective barrier. People with skin conditions like eczema are also more vulnerable simply because their skin breaks down more easily and more often.
When Staph Becomes Serious
Most staph infections stay at the skin level and resolve with proper care. But staph can enter the bloodstream, and when it does, the consequences can be severe. In the United States, an estimated 119,000 staph bloodstream infections occur each year, resulting in roughly 20,000 deaths.
Once in the blood, staph bacteria can seed infections in distant organs. Up to 40% of bloodstream cases develop what’s called metastatic infection, where the bacteria settle in a new location. This can cause vertebral bone infections (often felt as worsening back pain), infected heart valves (endocarditis), joint infections, or abscesses in the kidneys or spleen. Warning signs of a bloodstream infection include persistent high fever, sweats, new joint or back pain, and feeling severely ill in a way that’s clearly different from a localized skin problem.
Toxic shock syndrome is another rare but dangerous complication. It occurs when staph bacteria produce a toxin that triggers a body-wide inflammatory response. Symptoms come on suddenly and include high fever, a widespread sunburn-like rash, a dangerous drop in blood pressure, vomiting or diarrhea, and confusion. This is a medical emergency.
MRSA vs. Regular Staph
You’ve likely heard of MRSA, which stands for methicillin-resistant Staphylococcus aureus. The key difference is that MRSA strains have developed resistance to an entire class of commonly used antibiotics, making them harder to treat. Standard staph (sometimes called MSSA, for methicillin-susceptible) responds to a wider range of medications.
Hospital-acquired MRSA bloodstream infections have been declining over the past decade, dropping about 7% per year in recent tracking periods. Community-acquired MRSA rates have plateaued. Meanwhile, standard staph infections picked up outside hospitals have been slowly increasing, about 4% per year. MSSA now causes roughly half of all healthcare-associated staph infections, a reminder that antibiotic-susceptible strains still cause plenty of serious illness.
Mortality rates reflect where and how the infection is acquired. For bloodstream infections that develop in the hospital, MRSA carries about a 29% mortality rate and MSSA about 24%. For infections that start in the community, those numbers drop to 18% and 14%, respectively. The higher hospital rates partly reflect the fact that hospitalized patients tend to be sicker to begin with.
How Staph Infections Are Treated
Treatment depends entirely on the severity of the infection. For minor skin infections like folliculitis, washing the area and applying a topical antibiotic ointment may be sufficient. Warm compresses can help draw pus to the surface of a small boil and encourage it to drain on its own.
Larger or deeper abscesses often need to be drained by a healthcare provider, who makes a small incision to release the pus. This drainage is sometimes the most important part of treatment, even more so than the antibiotics that typically follow. For skin infections that need oral antibiotics, commonly prescribed options include drugs in the cephalosporin or tetracycline families. If MRSA is suspected or confirmed, the antibiotic choice narrows to the drugs that resistant strains still respond to.
Bloodstream or organ infections require intravenous antibiotics in a hospital setting, often for weeks. Recovery from invasive staph infection can be prolonged, and imaging studies are typically used to check whether the bacteria have seeded infections in the heart, bones, or other organs.
Practical Steps to Prevent Infection
Prevention comes down to two things: keeping bacteria out of wounds and limiting transmission between people. Cover any cuts or scrapes with a clean bandage until they’re fully healed. Don’t pick at or pop any sore that looks infected, since the pus can spread bacteria to other skin areas or to surfaces that others touch.
Wash your hands frequently, especially after touching a wound or changing a bandage. Don’t share towels, washcloths, razors, or athletic equipment that contacts bare skin. Clean your body after exercise, particularly if you use shared gym equipment. In household settings where someone has had a staph infection, regularly cleaning high-touch surfaces can help break the cycle of reinfection, given how long the bacteria can persist on objects.
If you’re visiting someone in the hospital who has a staph or MRSA infection, the risk of catching it is very low. Cleaning your hands when entering and leaving the room is the single most effective precaution.