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The newspaper of The Johns Hopkins University September 4, 2007 | Vol. 37 No. 1
'Cruise Ship' Illness Challenging and Costly to Hospitals, Too

Norwalk virus outbreak at JHH in 2004 estimated at more than $650,000

By David March
Johns Hopkins Medicine

A review of measures taken to address a 2004 outbreak of the highly infectious Norwalk virus at The Johns Hopkins Hospital has provided the first solid documentation of expenses and efforts in the United States to stop the infection from spreading among patients, staff and visitors. Total hospital costs for the three-month outbreak — including extra cleaning supplies, staff sick leave, diagnostic tests, replacement staff, and salaries and lost revenue from closed beds — were estimated at more than $650,000.

The outbreak at The Johns Hopkins Hospital was one of at least 24 at Maryland hospitals during the first half of 2004. Norwalk virus is highly contagious because only small amounts, as few as 10 to 100 viral particles, can lead to infection. It is spread or passed from person to person through fecal matter when people fail to wash their hands properly after using the bathroom and when people touch the same objects, such as doorknobs.

"We hope our approach will help other hospitals prepare for or manage an outbreak," said Cecilia Johnston, an instructor in infectious diseases at Johns Hopkins who led the investigation.

"Outbreaks need to be identified quickly and dealt with immediately, and relying on standard infection control procedures is not adequate," she said. "It may be necessary to close the infected units, isolate the infection source, get strict on hand hygiene, conduct a thorough washing down of units and keep repeating these steps until the outbreak is stopped. Health care workers, especially, need to be vigilant about these steps because they are the group primarily affected by outbreaks."

Reporting in the Sept. 1 edition of the journal Clinical Infectious Disease, Johnston and her team of patient safety experts describe how an outbreak spread among 265 health care workers and 90 patients between February and May 2004.

No one at Johns Hopkins died from the infection, but 13 afflicted hospital staff either visited the emergency room for treatment or required hospitalization after becoming severely dehydrated. Norwalklike viruses, formally known as noroviruses, cause serious gastrointestinal illness for which no treatment currently exists except for keeping the patient well hydrated. Symptoms include nausea, vomiting, diarrhea and severe stomach cramps. Those infected generally recover on their own within two to three days after symptoms appear.

"Health care workers really do need to be on the lookout for norovirus infections, and if there is an outbreak, hospitals need to address it very aggressively," said senior hospital epidemiologist Trish Perl, a professor of medicine and pathology at the School of Medicine. "Our experience shows that people can get very sick and that it costs a lot to fix the problem and address disruptions to staffing."

First reported in the coronary care unit, the Johns Hopkins Hospital outbreak quickly spread over a two-week period but remained clustered in that unit, a nearby echocardiography laboratory and a floor housing psychiatric services where patients and staff frequently interact, especially during group therapy sessions.

The outbreak was detected when two staff members who worked closely together became ill with diarrhea. Their illnesses were immediately reported to Johns Hopkins' infection control team, which monitors hospital operations daily for potential hazards to patient safety.

A norovirus outbreak was immediately suspected because there had been numerous reports of illness throughout the Baltimore region.

As part of their investigation, nurse managers began screening all staff and patients for any signs of gastrointestinal illness. Patient stool samples confirmed that the culprit was a norovirus, and genetic testing later verified that it was the same viral strain, genogroup II.4, that had caused a series of widely publicized outbreaks in nursing homes and on cruise ships traveling from Europe and the United States in 2002.

As the investigation proceeded, staff implemented strict precautions to control the outbreak and prevent it from spreading. Patients with symptoms were placed in isolation, by being moved either to private rooms or rooms with other sick patients. Group therapy sessions in psychiatry were temporarily halted, and no new patients were admitted to the units primarily affected. Sick staff members were sent home for as long as they had symptoms plus an additional 72 hours, sufficient time for the illness to no longer be contagious.

The investigation showed that many of the health care workers in the coronary care unit who initially had become ill had attended an outside social event where a nonstaff guest was already experiencing symptoms. Others likely became ill after touching a patient chart that had been handled by an ill colleague.

Standard precautions to guard against infection were followed, including a mandatory hospitalwide staff review of basic infection control procedures with an emphasis on more frequent hand washing, accompanied by a thorough washing down of all affected hospital facilities. The coronary care unit was closed for 24 hours to allow for a thorough cleaning, with all exposed surfaces getting washed down with bleach solution.

The easiest known way to kill noroviruses is through repeat washing of surfaces using bleach solutions containing at least 10 percent sodium hypochlorite. However, researchers say that even after intense cleaning efforts, norovirus particles have been found to cling to carpet surfaces, elevator buttons, bed rails and dining room tabletops.

To address any virus remaining, all disposable supplies in infected areas were thrown out and replaced, an effort that cost more than $53,000.

Because the norovirus outbreak was citywide, outside staff were not allowed to work at JHH, and Johns Hopkins staff, in turn, were banned from working at other facilities. Even visitors to the hospital were asked screening questions to identify stomach problems and, if present, were told not to see patients for 72 hours. Staff working on units hit by the outbreak wore gowns and gloves to guard against unwittingly picking up or spreading the disease. All group meals or shared-food events were banned inside the hospital.

After three months of intense efforts, by early May new infections had stopped. The outbreak was deemed over, and affected units returned to normal activity.

The researchers' review showed that the number of patients infected, the so-called attack rate of the virus, in the coronary care unit was low, at 5 percent (seven patients out of 133) but was notably higher for health care workers, at 30 percent (29 out of 97). The attack rate numbers were higher for psychiatry services, at 17 percent for patients (39 out of 233) and 38 percent for staff (76 out of 200).

Everyone infected experienced diarrhea or vomiting; some experienced chills and muscle aches.

Calculations of costs associated with the cleanup included expenses for cleaning supplies ($96,000), staff sick leave and overtime ($89,000) and lost revenue from closing the units and echocardiogram laboratory to new patients ($418,000). Indeed, nearly 460 hours of sick leave were used by staff on the coronary care unit, 138 hours in the echocardiogram lab and more than 2,000 hours in psychiatry services.

Expenses not taken into account were those associated with areas of the hospital where few cases were reported and no restrictions were placed on the unit. Costs incurred outside of main units were not included in this estimate because researchers were not certain that the infection had resulted from contact within the hospital rather than from exposure in the community. In addition, costs associated with lengthier stays in the hospital and more intensive patient care were not factored into the estimates because researchers would have had to guess at what the patients' length of stay would have been in the absence of a norovirus outbreak.

Researchers say their next step is to evaluate which specific infection control strategies and procedures are most effective at preventing noroviruses from spreading.

The U.S. Centers for Disease Control and Prevention estimate that each year more than 23 million people become infected with Norwalk or Norwalklike viruses, and the disease is considered a leading cause of foodborne illness, after people have contaminated food with dirty hands.

Funding for the study was provided by The Johns Hopkins Hospital. Testing services were provided by the Maryland Department of Health and Mental Hygiene, with additional confirmations provided by the National Institutes of Health.

In addition to Perl and Johnston, members of the Johns Hopkins team involved in this investigation and study were Haoming Qiu, John Ticehurst, Conan Dickson, Patricia Rosenbaum, Patricia Lawson, Amy Stokes, Charles Lowenstein, Michael Kaminsky, Sara Cosgrove and Kim Green.


Related Web site

Johns Hopkins Department of Hospital Epidemiology and Infection Control


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