Norovirus outbreak aboard USNS Mercy during Pacific Partnership 2015 Phillip R. Perrinez1, MD, PhD; Mari K. Brown2, MPH, MS; Drake H. Tilley3, MD, MPH&TM 1Departments of Internal Medicine and 3Infectious Diseases, Naval Medical Center, San Diego, CA 92134 2Navy Environmental and Preventive Medicine Unit Five, San Diego, CA, 92136

Date # Cases Intervention

Rate of GI Illness Observed (17 May – 05 Aug 2015) Epidemic Curve 20-Jul 0 Case Distribution αP = 9.2% II 69% of cases Baseline Incidence (3-day) 18 21-Jul 4 I • Stool PCR (+) for NoV. 30 • Berthing heads and galley disinfected using 22-Jul 8 II 26 3.5 16 virucidal agent. **OUTBREAK** 25 • NoV outbreak identified. 3 14 • Berthing heads disinfected. III • Crew education on risk for nosocomial 23-Jul 12 III 2.5 12 transmission. (Hand washing). 20 • Crew encouraged to seek medical attention if symptomatic. 10 IV 2 HAWAII FIJI PNG • Quarantine initiated (symptomatic). VI 24-Jul 11 IV 15 25-27 MAY 07-18 JUNE 27 JUNE-10 JULY • Discontinued self-service food items. 8 αA/B = 4.1% αCDEF = 3.7% αMO = 5.5% αFO = 3.4% 1.5 Cases of Number • NoV brief added to closed-circuit TV (continuous 25-Jul 6 V I loop). 6 10 9

1 ROXAS CITY, PI V VII 26-Jul 6 VI • Reinforced disinfection guidelines. Cases of Number 7 18 JUL-03 AUG 4 27-Jul 5 5 0.5 5 4 4 4 4 4 Cumulative Incidence (%) Incidence Cumulative Liberty Call 28-Jul 7 3 2 2 Arrive Roxas City • Ladderwells, passage ways, common areas VIII 29-Jul 5 VII 0 disinfected. 0 0 18-Jul 19-Jul 20-Jul 21-Jul 22-Jul 23-Jul 24-Jul 25-Jul 26-Jul 27-Jul 28-Jul 29-Jul 30-Jul 31-Jul 1-Aug 2-Aug 3-Aug 30-Jul 3 A B C D E F G H MO FO CPO 31-Jul 1 MAY JUNE Date JULY AUGUST Date of Symptom Onset Berthing αH = 25% 01-Aug 0 VIII • Quarantine lifted. 36% of cases

INTRODUCTION Case Definition What is an Outbreak? USNS Mercy (Roxas City) RESULTS Definition: Occurrence of a medical condition that exceeds the baseline/expected Average Census 1023 USNS Mercy is a U.S. Navy hospital ship routinely deployed to Southeast Symptom Number (n) Frequency (%) rate within a specific place or group over time. No. Cases 72 A NoV outbreak was detected from 17JUL2015 to 03AUG2015. The Asia to provide humanitarian assistance and disaster response support. Diarrhea 65 90 No. Controls 180 baseline incidence of GI-related illness was 0.4% (σ ± 0.3%). Patients that Norovirus (NoV) infection is characterized by acute onset of nausea, Nausea 55 76 What is an Outbreak Investigation? Attack Rate (αo) 7.0% had diarrhea and nausea/vomiting were included as cases. A total of 72 vomiting, abdominal cramping, and non-bloody diarrhea. Both hospitals Vomiting 49 68 Objectives: cases were identified. The average census during this period was 1023 (α Demographics Case Control o and ships are prone to NoV outbreaks. Attack rates (α) in excess of 40% Abdominal Cramping/Pain 38 53 1. Determine the magnitude of illness aboard the ship. Body Aches 32 44 Gender = 7.0%). 5/6 stool samples tested were positive for NoV. Of the cases, have been reported aboard military and civilian ships. A NoV outbreak 2. Identify the pathogen causing the illness. Fever 16 22 Male 59 128 85% of patients presented to medical attention within the first 48 hours 3. Identify risk factors associated with the illness. was detected aboard USNS MERCY while in Roxas City, Philippines in July Cases Presenting ≤ 72 hrs  Index Female 13 52 after symptom onset. 36% of cases were identified from a single berthing 2015. This is the first known shipboard NoV outbreak where real-time Cases Presenting > 72 hrs  Nosocomial 4. Formulate control measures to prevent or stop the spread of illness. Mean Age (yrs) [σ] 30 [7.3] 30 [9.3] space (αb = 25%), and 69% of all cases were from berthing spaces molecular surveillance testing was used to facilitate detection and guide connected by a common ladderwell. Individuals who experienced the control measures. Exposure/Activity All Cases (n = 72) Controls (n = 180) OR (95% CI) p onset of symptoms within the first 72 hours were more likely to have Bay Bay Beach 29 141 0.19 (0.11-0.33) < 0.001 consumed raw oysters and/or shellfish [OR 7.18; 95% CI 3.13-16.5]. Noroviruses Coco Veranda 16 81 0.35 (0.19-0.65) < 0.001 CDC Vessel Sanitation Program (VSP) • Single-stranded RNA viruses Oysters/Shellfish 16 22 2.05 (1.01-4.15) 0.05 CONCLUSIONS Clinical Features Galley/MRE Only 9 2 12.7 (3.65-44.3) < 0.001 Survey of 50 NoV outbreaks aboard international Applies to cruise ships that: cruise ships (May 2011 – Nov 2015) • Acute gastroenteritis Exposure/Activity Index (n = 24) Controls (n = 180) OR (95% CI) p • Visit both foreign and U.S. ports. Hospital ships are particularly vulnerable to diarrheal outbreaks during - Non-bloody diarrhea, nausea/vomiting, abdominal cramps (low-grade fever + body aches) Bay Bay Beach 17 141 0.67 (0.26-1.73) 0.44 • Carry 13 or more passengers. Average Attack Rate (%) humanitarian or disaster relief missions that can, in turn, impact mission • Incubation (12-48 hrs); Illness duration (24-72 hrs) Coco Veranda 10 81 0.87 (0.37-2.07) 0.83 When does CDC conduct an investigation? Passenger Crew readiness and capacity. Implementation of a vigilant surveillance system Transmission (extremely contagious) Oysters/Shellfish 12 22 7.18 (3.13-16. 5) < 0.001 7.0 1.5 • If ≥ 3% of passengers or crew experience GI in coordination with point-of-care molecular diagnostics allowed for early • Person-person, foodborne, waterborne Galley/MRE Only 1 2 3.87 (0.40-37.7) 0.31 Max 21 6.4 illness, OR if an unusual GI illness pattern or detection and aggressive infection control measures to mitigate - Fecal-oral, aerosolized vomitus, fomites, contaminated surfaces Exposure/Activity Nosocomial (n = 48) Controls (n = 180) OR (95% CI) p Min 3.2 0.2 • Infectious dose: 18 viral particles Bay Bay Beach 12 141 0.09 (0.05-0.18) < 0.001 characteristic is identified. σ 3.4 1.1 transmission and limit the infectious burden during a NoV outbreak 9 • Viral shedding (stool): Peak 2-5 days following infection (100x 10 copies/gm) Coco Veranda 6 81 0.17 (0.08-0.40) < 0.001 aboard USNS Mercy. Oysters/Shellfish 4 22 0.65 (0.21-1.98) 0.61 METHODS Galley/MRE Only 8 2 17.8 (5.31-59.7) < 0.001 REFERENCES Syndromic diarrhea surveillance was performed during the Pacific 1. Corwin, A. L., Soderquist, R., Edwards, M., White, A., Beecham, J., Mills, P., Oyofo, B. Partnership mission from 17MAY2015 to 29SEP2015 and included all Pacific Partnership 2015 (1999). Shipboard impact of a probable Norwalk virus outbreak from coastal Japan. The personnel that presented to sick call with the chief complaint of nausea, American journal of tropical medicine and hygiene, 61(6), 898-903. USNS Mercy (T-AH 19) is a U.S. Naval hospital ship routinely deployed to South-East Asia to provide humanitarian assistance and disaster 2. Centers for Disease Control and Prevention (2011). Updated Norovirus Outbreak vomiting, or diarrhea. Multiplex PCR testing (FilmArray® system by response support as part of Pacific Partnership. Management and Disease Prevention Guidelines. MMWR 60(3), 1-20. Biomerieux) was used to identify infectious agents when increased rates 3. Centers for Disease Control and Prevention. Vessel Sanitation Program. Mission: U.S. Pacific Fleet annual humanitarian and civic assistance exercise aimed at strengthening international relationships with http://www.cdc.gov/nceh/vsp/default.htm, 14 Jan 2016. of diarrhea were observed. Basic demographic and clinical data were partner and host nations in the Asia-Pacific region. collected prospectively as part of the outbreak investigation. Early, 4. Gonzaga, V. E., Ramos, M., Maves, R. C., Freeman, R., & Montgomery, J. M. (2011). Partner Nations: United States, Australia, Japan, Malaysia, New Zealand, Canada, Fiji, Timor-Leste, Singapore, Republic of Korea, France. Concurrent outbreak of norovirus genotype I and enterotoxigenic Escherichia coli on a US aggressive control measures including isolation, hand washing campaigns, Navy ship following a visit to Lima, Peru. PloS one, 6(6), e20822. screening of food handlers, and decontamination of high traffic areas Host Nations: Fiji, Papua New Guinea, Philippines, Vietnam. 5. Navy and Marine Corps Public Health Center (2011). Norovirus Illness Prevention & Control Guidance for the U.S. Fleet. were implemented. USNS Mercy (T-AH 19) Statistics: 1,200 total personnel. 649 surgeries performed on board. Provided medical/dental care for > 16,000 patients at community health engagements (approximately 5200 in Philippines).

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