Norovirus Outbreak in a Long Term Care Facility: A Retrospective Epidemiological Study

Gillian Jones MBA MPH, PIDr. Tae Lee

Dr. Jason Brinkley

UMC-IRB # 09-0250

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Topics

• Study Objective

• Introduction

• Study Methods

• Study Results

• Control and Prevention

• References

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Study Objective

• OBJECTIVE: Perform descriptive epidemiology of Norovirus (NV) in a nursing home outbreak and examine patient risk factors in transmission of Norovirus caused gastroenteritis.

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Introduction

NOROVIRUS Basic Epidemiology

• Agent – Norovirus, or Norwalk-like virus, classified as calciviruses, thought to be the most

common causal agents of NONBACTERIAL gastroenteritis outbreaks.

• Reservoir – Humans only known reservoir

• Transmission Modes - probably by fecal-oral route, although in hospital setting

contact or airborne transmission from vomitus and fomites. Also community food borne, waterborne and shellfish transmission

• Season – common name winter vomiting disease , stomach flu, viral diarrhea

• Geography – worldwide and common

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Intro Cont’d-Clinical Manifestations

• Incubation Period – usually 24-48 hrs, but ranges from 10-50 hours

• Period of Communicability- during acute stage and up to 48 hours after diarrhea stops

• Characteristic Symptoms- N/V, diarrhea, abdominal pain, myalgia, h/a, malaise, low grade fever, or a combination

• Communicability – 48 hrs after last diarrhea, but viral shedding can occur from 7 days up to 2 weeks and infection risks unknown.

• Notorious Outbreak - The first recorded epidemic attributed to Norwalk virus occurred in an elementary school in Norwalk, Ohio, in 1968.

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Complications

Researchers hypothesized that certain persons might be genetically more susceptible to NLV infection and disease, in particular blood type O. If true, this hypothesis could explain why those with greater levels of preexisting antibody are more likely to experience NLV infection and disease after re-exposure to virus.

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People who get viral gastroenteritis almost always recover completely . HOWEVER:• Gastroenteritis is a serious illness, however, for persons who are unable to drink enough fluids to replace what they lose through vomiting or diarrhea.

•Infants, young children, and persons who are unable to care for themselves, such as the disabled or elderly, are at risk for dehydration from loss of fluids.

• Immune compromised persons are at risk for dehydration because they may get a more serious illness, with greater vomiting or diarrhea.

•They may need to be hospitalized for treatment to correct or prevent dehydration.

USA• CDC estimates that 23 million cases of

acute gastroenteritis are due to Norovirus infection, and it is now thought that at least 50% of all food borne outbreaks of gastroenteritis can be attributed to noroviruses.

• Among the 232 outbreaks of Norovirus illness reported to CDC from July 1997 to June 2000, 57% were food borne, 16% were due to person-to-person spread, and 3% were waterborne; in 23% of outbreaks, the cause of transmission was not determined. In this study, common settings for outbreaks include restaurants and catered meals (36%), nursing homes (23%), schools (13%), and vacation settings or cruise ships (10%).

North Carolina Dec08-Feb09*

Month # LTC Bldgs #Pts.

Dec 6 104

Jan 9 134

Feb 6 83

Tot 19 321

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Incidence Reported Cases

*all counties Forsyth and eastward-only 2 outbreaks NV+state ref lab confirmed

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Host Risk Factors

• Demographics – Very Young under 5yo or very old over 65 yo

• Nutritional status if compromised

• Immune Status if compromised

• Other- close quarters such as cruise ships, camps, acute and long term care settings

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Study Methods

• Epidemiological data and lab results collected in post-outbreak observational study

• Setting 150 bed nursing home facility in eastern North Carolina.

• Case status, symptom characteristics and potential risk factors identified using Medical-record review, 24-hour reports of change of condition and patient quarterly assessment.

• Financial and staff related data identified through key informant interview.

• De-identified data used in analysis.

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• Data entered into Excel 2007 and Powerpoint2007 for exhibits

• Data entered into GOATv2.1 (general outbreak analysis tool) used by NCPH Regional Surveillance Team Six with Epi Info v3.5.1

• Data entered into PASW 17.0 for frequencies

• Data entered into JMP univariate analysis, correlations, exhibits

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Methods cont’d

RESULTS: • An outbreak duration of 15 days with 2.2 median

days illness affected 97 patients (66%) and 24 staff (15%) with symptoms of acute gastroenteritis.

• 71 patients met case definition, 49.6% patient-case attack rate. Ten patients required in house oral and IV rehydration, six patients required hospital evaluation, and one patient with co-morbidities died. A source case was identified.

• No association between food or water consumption and symptoms was identified after environmental testing of water, ice and food service.

• A NV strain in the Genogroup type II was identified.

• Residents were at higher risk of infection if they were physically dependent on staff care with a dependency score lower than ten {RR} of 1.22 95 %CI (range 0.60-2.47) or had an ill roommate {RR} of 1.23 95% CI (range 0.86-1.78).

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Results- OVERVIEW

• The average patient who became ill was an African American or Caucasian female with mean age of 83 years old; residents without illness were 7.5 years younger (mean age 75.5, p=0.06) There were no significant differences in race associated with increased risk of infection (59% African American) but there was in gender.

• Sixty - four patient-cases (89% of the infected cases) were female and seven patient-cases (13%) were male patient-cases at the facility. Sixty six percent (66%) of all the women in the retrospective cohort meeting case definitions were infected compared with thirty two percent (32%) of the men.

• Female RR=1.20 (95% CI 1.99 -1.43, p = 0.03).

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Results- PERSON

FACILITY FLOORPLAN

1. Both nursing units and all six wards had patients exhibiting acute gastroenteritis (AGE) symptoms

1. Four of the six wards also had confirmed NV lab specimens (see Figure 1 NV lab confirmed case-patient rooms indicated with red dots).

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Results-PLACE

LTC FACILITY 12-08/1-09

LEGEND - NOROVIRUS

symptomatic NV lab confirmed

• Time1. Outbreak duration of 15 days

2. 2.2 median days illness (range .5 -8 days)

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Results-

Day 5 Clinical outbreak protocol begins

Day 8 NV lab confirmed, Enhanced Measures begun & LHD Notified

Day 13 Last New Onset

Day 1 Index Case Report

Day 8 LHD & SHDNotified

Day 8 Ban on

admissions & transfers begins

Table 1

SYMPTOMS OF CASE-PATIENTS OF A LONG-TERM–CARE FACILITY DURING A NOROVIRUS OUTBREAK FROM DECEMBER 29, 2008 TO JANUARY 13, 2009*

_____________________________________________________________________________Characteristic CASE-Patient n/N (%)________________________________________________________________________• Female 67/126 (87% of cohort ) • Age 83 yo (range 53 to 105 years)• Peak illness onset dates January 6, 2009 • Illness Duration 15 days (Dec 29’08-Jan 13,’09) • Median duration of illness in days 2.2 days (range 0.5- 9 days) • †Median no. Co-Morbidities 1.8 (range 0-4)

• Symptom• Diarrhea 67/71 (94 % of ill)

• Median number of stools in a 24 period 3.5 (range 2-6)

• Median days duration of diarrhea 2.1 (range1-5) • Nausea

8/71 (10.4% of Ill)• Vomiting

53/71 (68.8% of Ill)• Abdominal cramps

1/71 (1% of Ill)• Low Temp

31/71 (40.2% of Ill)

• Maximum Temp 100.5 F

• Headache & Myalgia 1/71 (1% of Ill)

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Results- Symptoms

Risk Factor Symptomatic no Symptoms RR CI Range P/Test

________________________________________________________________________• Female 63 40 1.19 95(1.99 -1.43)

P 0.03* • Male 8 14 0.453 95 (0.19 -0.96)

P 0.03*

• Caucasian 30 16 1.426 95(0.87-2.33)

P 0.15

• Sick Roommate 40 24 1.23 95(0.85-1.78)

P 0.24

• <3 days ill 39 54 1.82 95(1.47-2.25)

P<.0001*

• >1 day ill 60 54 1.18 95(1.07-1.31)

P 0.0025*• Lived on M ward 6 14 0.32 95(0.134-0.792)

P 0.0083*• ADL<10score Dependency 16 10 1.217 95(0.60-2.46)

P 0.584

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Results- Risk Factors

Preventive Measures

• Preventive measures: Frequently wash your hands, especially after toilet visits and changing diapers and before eating or preparing food.

• Carefully wash fruits and vegetables, and steam oysters before eating them. • Thoroughly clean and disinfect contaminated surfaces immediately after an

episode of illness by using a bleach-based household cleaner. • Immediately remove and wash clothing or linens that may be contaminated with

virus after an episode of illness (use hot water and soap). • Flush or discard any vomitus and/or stool in the toilet and make sure that the

surrounding area is kept clean. • Persons who are infected with Norovirus should not prepare food while they have

symptoms and for 3 days after they recover from their illness • Use hygiene measure applicable to diseases transmitted via fecal-oral route and

respiratory hygiene if vomitus prevalent due to airborne droplets

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Control Measures

• Surveillance: Report to local health authority: obligatory report of epidemics in some countries, no individual case report required.

Surveillance of Norovirus Infection in the United States• CDC currently does not conduct active surveillance to monitor outbreaks of gastroenteritis caused by

noroviruses. Outbreaks are reported to CDC's Viral Gastroenteritis Section, Respiratory and GastroentericViruses Branch, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases (NCIRD) when states send specimens for testing or sequencing, or outbreaks are reported directly by states to the electronic database (eFORS) maintained by the Foodborne Diarrheal Diseases Branch. For further details please email calicinet@cdc.gov

• Confirmations: Lab stool and serum cultures- Virus may be identified in stools through RT-PCR reverse transcription polymerase chain reaction and antigen assays. In addition, several epidemiologic criteria have been proposed for use in determining whether an outbreak of gastroenteritis is of viral origin. Kaplan's criteria for this purpose are as follows: 1) a mean (or median) illness duration of 12 to 60 hours, 2) a mean (or median) incubation period of 24 to 48 hours, 3) more than 50% of people with vomiting, and 4) no bacterial agent previously found. Although quite specific, these criteria are not very sensitive, and therefore the possibility of a viral etiology should not be discarded if the criteria are not met.

• Precautions: control patient, contacts and the immediate environment

• Isolation of cases – Enteric precautions,-No quarantine

• Disease specific treatment-Fluid and electrolyte replacement in severe cases. In children aged less than five, give 10 mg elemental zinc per day for 10-14 days. Products like pedialyte and gatorade used

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Future Directions in the USA

Challenges: • In addition to fecal/oral spread, Norovirus disease can spread via droplets from vomitus (person to

person transmission) . So facilities must focus on methods to limit transmission including isolation precautions (e.g., cohort sick patients in a healthcare facility) and environmental disinfection.

Noroviruses are highly resistant to standard sanitation measures. They are able to survive freezing, temperatures as high as 60°C, and have even been associated with illness after being steamed in shellfish. Moreover, noroviruses can survive in up to 10 ppm chlorine, well in excess of levels routinely present in public water systems.

• Epidemic measures: Search for vehicles of transmission and source but don’t wait for lab confirmations, need to implement control measures immediately.

• Disaster implications: Large-scale outbreaks could be a potential problem if water supplies or food preparation below hygiene standards.

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Conclusions

•NV likely spread in the long-term facility through person to person .

•Multi disciplinary enhanced hygiene measures limited outbreak to fifteen days.

• Implementation of clinical, administrative, and health department control measures should not wait for lab confirmation of specimens.

•Airborne and droplet transmission would be very unusual for norovirus.

•Aerosolization due to dry vacuuming of vomitus has been documented, but spread is mostly it is s person to person through shared contact with contaminated items or foods.

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REFERENCES

The Big Picture Book of Viruses: http://www.virology.net/Big_Virology/BVRNAcalici.html•ICTVdB Management (2006). 00.012. Caliciviridae. In: ICTVdB - The Universal Virus Database, version 3. Büchen-Osmond, C. (Ed), Columbia University, New York, USA

•http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-factsheet.htm

•Heijne JC, Teunis P, Morroy G, et al. Enhanced hygiene measures and norovirus transmission during an outbreak. Emerg Infect Dis. 2009;15(1):24-30.

•Norwalk-Like Viruses:' Public Health Consequences and Outbreak Management," MMWR, June 01, 2001 / 50(RR09);1-18

•Marx A, Shay DK, Noel JS, et al. Outbreak of acute gastroenteritis in a geriatric long-term-care facility: combined application of epidemiological and molecular diagnostic methods. Infect Cont Hosp Epidemiol 1999;20:306--11.

•Jiang X, Turf E, Hu J, et al. Outbreaks of gastroenteritis in elderly nursing homes and retirement facilities associated with human caliciviruses. J Med Virol 1996;50:335--41.

• Rao S, Scattolini de Gier N, Caram LB, Frederick J, Moorefield M, Woods CW. Adherence to self-quarantine recommendations during an outbreak of norovirus infection. Infect Control Hosp Epidemiol. 2009;30(9):896-899.

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Acknowledgements

Thank you to the subject facility, the local county Health Department,

and the North Carolina State Public Health Department epidemiology staff

who provided information about the winter ’08 outbreak season.

Also thank you to Dr. Tae Lee, Dr. John Morrow, Mr. Hal Garland,

Dr. Christopher Mansfield, Suzanne Lea, Dr. Andrada Ivanescu,

and Dr. Jason Brinkley for content advice and manuscript review.