A MRSA expert who was not involved in the research said it "confirms what we've suspected all along."
"Transmission is a function of contact and time," said Dr. Henry Chambers, chair of the antimicrobial resistance committee for the Infectious Diseases Society of America. "At the end of the day, who are you in contact with the most? Your family."
If you have a MRSA infection, how do you protect your family members? "Basically, it boils down to keeping the wound covered, and frequent hand washing," Chambers said.
According to Uhlemann, you can also use bleach to clean surfaces, and hot water to wash bedding and clothes that an infected person has used. Chambers said the role of surfaces in transmitting MRSA is not "well delineated." But, he added, "it's good to clean."
The U.S. Centers for Disease Control and Prevention estimates about one in three people carries staph bacteria in the nose, usually without sickness. About 2 percent of people harbor MRSA.
It's thought the superbug spread into the wider community because of antibiotic misuse and overuse. When bacteria are exposed to an antibiotic but survive, they can quickly mutate to become resistant to that drug.
Uhlemann's team found some more evidence to point the finger at antibiotic misuse. They discovered that mutations in USA300 that confer resistance to antibiotics called fluoroquinolones (such as ciprofloxacin, sold as Cipro) may have emerged around 1995 in New York City. Fluoroquinolone prescriptions would later soar nationwide -- by about 50 percent between 1999 and 2008, the study says.
So it's possible that widespread use of those drugs helped the resistant USA300 strain spread.
"This, once again, argues for the careful use of antibiotics," Uhlemann said.
Chambers agreed. "We know that about half of antibiotics prescribed aren't needed," he said.
Antibiotics kill only bacteria, so they are useless against viral infections such as the common cold and should not be prescribed for those illnesses. If you do need an antibiotic, experts say it's important to take the full course. Stopping too soon could allow some bugs to survive and develop resistance to the drug.