Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

American hospitals may have made a little progress in fighting one of the biggest problems threatening patients: infections they get while in the hospital.

A new survey by the Centers for Disease Control and Prevention shows that the rate of hospital acquired infections has gone down a little bit.

"We see things going in the right direction," said Dr. Shelley Magill, who led the CDC study team.

In 2011, when the CDC last did a survey, about 4 percent of patients got an infection in the hospital. Now that number is down to 3.2 percent, the CDC team reported in the New England Journal of Medicine.

"Patients' risk of having a healthcare associated infection was 16 percent lower in 2015 than in 2011," the CDC-led team wrote.

The numbers are still enormous. That 4 percent of hospitalized patients with a healthcare associated infection extrapolated to 648,000 patients across the country in 2011.

The CDC team doesn’t count every single infection, but instead enlisted 200 hospitals in 10 states. They asked the hospitals to choose a random sample of patients on a single day and check their records to see if they had an infection that they would have caught because they were in the hospital.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Of the 12,299 patients in the survey, 394 had a healthcare-associated infection. "Pneumonia, gastrointestinal infections and surgical-site infections were the most common health care-associated infections," the team wrote.

The Health and Human Services Department has led a push to reduce hospital infections, and has started penalizing hospitals that take part in Medicare if they do not improve infection rates.

They have focused on several types of preventable infections in particular, including surgical-site infections, urinary infections caused by catheter use and infections linked with the use of central lines inserted to develop drugs over a long time, such as chemotherapy or intensive antibiotic treatment.

Another focus has been on reducing Clostridium difficile or C. diff infections, which are very common in people who take antibiotics for long times.

"Pneumonia, gastrointestinal infections and surgical-site infections were the most common health care-associated infections," the team wrote.

The biggest reduction, the CDC team found, was in catheter-associated infections.

"These results provide evidence of national success in preventing healthcare-associated infections, particularly surgical-site and urinary tract infections," they wrote.

But C. diff infections and pneumonia were just as common as before. "Pneumonia was definitely one infection where we did not see an improvement," Magill told NBC News.

To the researchers’ surprise, most of the pneumonia cases were not caused by ventilator use. Patients who are on ventilators are susceptible to pneumonia, but careful techniques and simple interventions such as raising a patient’s head a little can help prevent pneumonia.

Magill says healthcare professionals still struggle to fight pneumonia, which can be caused by a range of bacteria and viruses, as well as fungal infections.

"We don’t know how to prevent pneumonia in the hospital. We are all struggling to see how we can study it well in the hospital," said Dr. Ghinwa Dumyati, an infectious disease specialist who works at the University of Rochester Medical Center and who took part in the CDC surveys in 2011 and 2015.

Careful, meticulous technique can prevent infections caused by central lines and catheters. The survey also found a reduction in overall use of catheters, which may have helped lower infection rates.

Training staff in these techniques may have helped lower infection rates in New York, Dumyati said.

"Just by doing simple things such as paying attention when you insert the line and paying attention when you are manipulating the line can lead to dramatic reductions," she said.

"It takes time to see change, but the change is happening."

In the meantime, patients, their friends and family should keep an eye out to make sure everyone who enters a room follows strict hygiene measures such as washing hands and hospitals should keep staff aware of the need to stick to meticulous protocol.

The CDC is also due to release a report on infections in nursing homes. Earlier this month, nine children in a long-term rehabilitation center in New Jersey died of adenovirus infections during an outbreak.