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Published Date: 2005-10-16 23:50:00
Subject: PRO/EDR> Viral gastroenteritis update 2005 (15)
Archive Number: 20051016.3017

VIRAL GASTROENTERITIS UPDATE 2005 (15)
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Date: Fri 14 Oct 2005
From: ProMED-mail <promed@promedmail.org>
Source: MMWR Morb Mortal Wkly Rep 2005; 54(40); 1016-8, Fri
14 Oct [edited]
<http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5440a3.htm>

During the week after Hurricane Katrina struck the Gulf
Coast of the US on 29 Aug 2005, an estimated 240 000
persons, mostly from Louisiana, evacuated to Houston, Texas.
On 31 Aug, an estimated 24 000 evacuees were sheltered
temporarily at facilities in Reliant Park, a sports and
convention complex that includes Reliant Astrodome, Reliant
Center, and Reliant Arena. All evacuees to these 3
facilities were provided with cots, bedding, food, water,
and access to lavatories and showers. A medical facility was
set up initially to provide emergency care to evacuees and
subsequently to serve as a comprehensive outpatient clinic
staffed largely by personnel from the Harris County Hospital
District (HCHD), Baylor College of Medicine (BCM), and Texas
Children's Hospital (TCH). On 2 Sep 2005, physicians and
staff from Harris County Public Health and Environmental
Services (HCPHES) noted a substantial number of adults and
children with symptoms of acute gastroenteritis (defined as
diarrhea and/or vomiting) at the medical clinic in Reliant
Park. In collaboration with HCPHES, CDC and medical
personnel of HCHD, BCM, and TCH conducted enhanced
surveillance to improve identification of acute
gastroenteritis, investigate the apparent outbreak, identify
the infectious agent, and implement measures for its
control. This report summarizes the preliminary
epidemiologic data from this investigation and underscores
the challenges to managing a large and rapidly spreading
outbreak of norovirus in crowded evacuee settings.
A simple checklist of symptoms was used by HCPHES to collect
data on a triage intake form. Data were used as an index of
medical problems and care delivered. This information was
gathered and entered into a centralized database nightly by
HCPHES staff members, and results were distributed to the
surveillance team each morning.
During the period 2-12 Sep 2005, about 6500 of the estimated
24 000 evacuees visited the Reliant Park medical clinic, and
1169 (18 per cent) reported symptoms of acute
gastroenteritis. 3/4 of the patients with acute
gastroenteritis symptoms were adults (aged under 18 years)
residing in the 3 facilities housing evacuees at Reliant
Park or in smaller shelters and hotels in Houston. The
number of acute gastroenteritis cases peaked on 5 Sep 2005,
when 211 persons reported acute gastroenteritis symptoms,
and cases declined slowly thereafter. A total of 511 (44 per
cent) patients reporting acute gastroenteritis symptoms had
diarrhea alone, 342 (29 per cent) reported vomiting, and 316
(27 per cent) reported both diarrhea and vomiting. During
the period 2-12 Sep, about 14 per cent of adult visits to
the medical clinic and 28 per cent of pediatric visits were
for acute gastroenteritis; on peak days, these figures
reached 21 and 40 per cent, respectively (other common
reasons for visits were chronic diseases and medication
refills). In addition, medical personnel, police officers,
and volunteers who had direct contact with patients reported
acute gastroenteritis symptoms, suggesting substantial
secondary spread, presumably by person-to-person contact or
fomite transmission. The number of hospitalizations was
unknown; no deaths were reported.
To determine the etiologic agent, stool samples (either
rectal swabs or bulk stools) were sent to one of several
laboratories of HCHD, BCM, and TCH for diagnosis of
bacterial, parasitic, and viral enteropathogens. In stool
samples from 44 patients tested by reverse
transcription-polymerase chain reaction, norovirus was
confirmed in 22 (50 per cent) specimens; no other
enteropathogen was identified. Sequencing to determine viral
strains is being conducted but is not yet complete.
At the onset of the outbreak, health authorities implemented
extensive infection control measures. Patients with acute
gastroenteritis who were dehydrated were rehydrated in a
separate observation area reserved for patients with
suspected infectious illness and then transferred to an
isolation area for at least 48 hours after vomiting and
diarrhea had ended. In addition, alcohol-based gel hand
sanitizers were distributed throughout the facilities and
near lavatories, and a bank of portable sinks was installed
inside the medical clinic. Medical staff, disaster relief
personnel, volunteers, and evacuees were all alerted to the
heightened need for using proper hand washing techniques
through medical staff meetings, posters, banners, and
newsletters distributed to all evacuees. Despite these
timely interventions, the outbreak continued for more than 1
week but declined before the evacuees vacated Reliant Park
in late September 2005.
(Reported by: H Palacio, MD, U Shah, MD, C Kilborn, MPH, D
Martinez, MPH, V Page, MPH, Harris County Public Health and
Environmental Svcs; T Gavagan, MD, K Mattox, MD, H DuPont,
MD, MK Estes, PhD, R Feigin, MD, RL Atmar, MD, FH Neill, J
Versalovic, MD, PhD, C Stager, PhD, D Musher, MD, Texas
Children's Hospital, Baylor College of Medicine, and Harris
County Hospital District, Houston, Texas. RI Glass, MD, PhD,
Div of Viral and Rickettsial Disease, National Center for
Infectious Diseases; M Faul, PhD, Div of Injury and
Disability Outcomes and Programs, National Center for Injury
Prevention and Control; M Davies, MD, North Carolina Dept of
Health and Human Svcs; M Cortese, MD, Div of Epidemiology
and Surveillance, National Immunization Program; E Lau, MD,
EIS Officer, CDC.)
MMWR editorial note
-------------------
The epidemiologic and laboratory findings in this report
suggest that an outbreak of norovirus gastroenteritis might
have affected about 1000 evacuees and relief workers in 3
facilities at Reliant Park and in other Houston facilities
that housed evacuees, including a convention center, smaller
shelters, and hotels. The rapidly changing population of
evacuees treated at the medical clinic complicated efforts
to monitor the magnitude of the outbreak or the extent of
disease among evacuees in Reliant Park. Nonetheless, on some
days, nearly 21 per cent of adults and 40 per cent of
children visiting the Reliant clinic had acute
gastroenteritis, confirming the importance of this problem.
Conditions that might have facilitated virus transmission
included crowding, insufficient sanitation in lavatories,
lack of an adequate number of hand washing facilities, and
delays in cleaning and decontaminating soiled areas and
bedding. In addition, initial isolation procedures were
difficult to maintain over time because family members
already traumatized by displacement, grief, and personal
loss were separated from each other because of illness.
Noroviruses are the commonest cause of outbreaks of acute
gastroenteritis in the United States. Outbreaks not
associated with contaminated food or water but spread
through person-to-person contact or from fomites tend to
occur in crowded settings, such as cruise ships, camps,
shelters, and hospital wards (1-4). Persons infected with
norovirus have an acute onset of vomiting and/or non-bloody
diarrhea lasting 12-60 hours, with an incubation period of
24 to 48 hours (5). Certain persons do not become ill when
infected, which might be associated with a genetic
predisposition to infection conferred by blood group
antigens (6). Once an outbreak begins, norovirus is highly
contagious and easily transmitted via multiple routes
because of its low infectious dose (that is, fewer than 100
viral particles), its ability to persist in the environment,
and its resistance to inactivation by multiple cleaning
agents (5,7).
Furthermore, diagnosis of norovirus through laboratory
testing is not widely available, making confirmation of
norovirus as the etiologic agent in these types of outbreaks
difficult.
Although the challenges to preventing and managing norovirus
outbreaks in a disaster relief situation are considerable,
certain lessons have been learned from this and other
norovirus outbreaks. Early surveillance and identification
of outbreaks of acute gastroenteritis with rapid detection
of the causative agent are essential to implement timely,
focused, and effective interventions. In particular,
vigilance to hand washing techniques; accessibility to soap
and water within medical facilities, eating and food
preparation areas, lavatories, and showers; and containment
and disinfection of soiled areas and bedding can all help
decrease the spread of norovirus. These needs warrant
special attention in planning and managing a disaster relief
facility (8,9). When feasible, isolation of patients who are
actively vomiting or continue to have diarrhea can be
instituted, but care should be taken not to further distress
traumatized evacuees.
Norovirus should be suspected when outbreaks of acute
gastroenteritis occur in a crowded setting, on the basis of
its epidemiologic features (rapid spread and secondary
transmission) and clinical presentation (high prevalence of
vomiting). Persons with norovirus gastroenteritis should be
treated promptly with rehydration, and measures to prevent
secondary transmission (promoting proper hand washing
techniques and cleaning and disinfecting soiled surfaces)
should be taken immediately; however, these measures give no
absolute assurance against further spread of norovirus
(5,10). The outbreak described in this report was identified
early and managed aggressively. However, rapid, sensitive
laboratory assays are still needed to detect norovirus and
to provide a better understanding of the most effective
intervention strategies in crowded evacuee environments.
References
----------
[1] CDC. Norovirus activity -- United States, 2002. MMWR
2003; 52: 41-5.
[2] Lopman BA, Reacher MH, Vipond IB, Sarangi J, Brown DW.
Clinical manifestation of norovirus gastroenteritis in
health care settings. Clin Infect Dis 2004; 39: 318-24.
[3] CDC. Outbreaks of gastroenteritis associated with
noroviruses on cruise ships -- United States, 2002. MMWR
2002; 51: 1112--5.
[4] CDC. Outbreak of acute gastroenteritis associated with
Norwalk-like viruses among British military
personnel---Afghanistan, May 2002. MMWR 2002; 51: 477-9.
[5] CDC. "Norwalk-like viruses": public health consequences
and outbreak management. MMWR 2001; 50(No.RR-9).
[6] Hutson AM, Atmar RL, Graham DY, Estes MK. Norwalk virus
infection and disease is associated with ABO histo-blood
group type. J Infect Dis 2002; 185: 1335-7.
[7] Becker KM, Moe CL, Southwick KL, MacCormack JN.
Transmission of Norwalk virus during football game. N Engl J
Med 2000; 343: 1223-7.
[8] CDC. Guidelines for environmental infection control in
health-care facilities: recommendations of CDC and the
Healthcare Infection Control Practices Advisory Committee
(HICPAC). MMWR 2003; 52(No.RR-10).
[9] CDC. Guideline for hand hygiene in health-care settings:
recommendations of the Healthcare Infection Control
Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA
Hand Hygiene Task Force. MMWR 2002; 51(No.RR-16).
[10] CDC. Managing acute gastroenteritis among children:
oral rehydration, maintenance, and nutritional therapy. MMWR
2003; 52(No.RR-16).
--
ProMED-mail
<promed@promedmail.org>
[This epidemiological analysis of infectious disease
problems associated with the emergency evacuation of large
numbers of people away from the path of hurricane Katrina
has identified the following:
(1) control and treatment of gastroenteritis as one of the
immediate challenges;
(2) norovirus infection was confirmed as the etiologic agent
in 50 per cent of cases; and
(3) facilities and reagents for the laboratory diagnosis of
norovirus infection are not widely available despite its
predominant role.
- Mod.CP]

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