Methicillin-resistant Staphylococcus aureus (MRSA) infections among hospital intensive care unit (ICU) patients with intravenous tubes dropped by about 50% between 1997 and 2007, according to a new report.

Researchers at the Centers for Disease Control and Prevention looked at MRSA infection rates at more than 1,600 ICUs. They found that 43 out of every 100,000 patients with IV tubes were infected with MRSA in 1997. By 2007, that number decreased to 21. Rates of less resilient staph infections were also on the decline during that period, according to the report. MRSA is estimated to cause up to 19,000 deaths a year, and up to 85% of infections occur in nursing homes, hospitals and other healthcare settings.

Researchers did not study the cause of the drop in infections, only the rates of infection, so they cannot address the cause of the decline, according to the Los Angeles Times. Many states have passed laws in recent years requiring stringent infection control policies in healthcare settings, including frequent hand washing and patient screening. But physician groups and hospitals have said these policies neither are scientifically proven nor cost-effective, the Times reports. The report was published Wednesday in the Journal of the American Medical Association.