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
"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
pathology at the School of Medicine. "Our experience
that people can get very sick and that it costs a lot to
fix the problem and address disruptions to
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
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
Researchers say their next step is to evaluate which
specific infection control strategies and
procedures are most effective at preventing noroviruses
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.