NOROVIRUSESpres

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Published on November 7, 2007

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FAMILY CALICIVIRIDAE: Noroviruses:  FAMILY CALICIVIRIDAE: Noroviruses Teresa Kunkel 4-16-04 Honors Virology Presentation To Be Discussed::  To Be Discussed: Taxonomy, structure and genome Disease manifestations and clinical symptoms Diagnosis Transmission Epidemiology and incidence Environmental resistance Prevention and Control Noroviruses Taxonomy:  Noroviruses Taxonomy Previously- Family Caliciviridae Genus: 1. Norwalk-Like Viruses (NLVs) 2. Sapporo-Like Viruses (SLVs) Recently- Genus Noroviruses (formerly Norwalk-Like Viruses) The Norovirus Genus:  The Norovirus Genus Norwalk Virus Desert Storm Virus Southampton Virus Snow Mountain Agent Hawaii Virus Toronto Virus Bristol Virus Jena Virus Viral Morphology:  Viral Morphology Non-enveloped, icosahedral 27-40 nm Single structural capsid protein, 60kD - 180 molecules, folds into 90 dimers Distinguishing characteristic: 32-cupped shaped depressions on the axes of the icosahedron Slide6:  Norovirus Structure by EM www.pubmed.gov PMID: 13679618 Genome:  Genome (+) ss RNA, 7900 nt in length 3 Open Reading Frames: ORF1= non-structural proteins- RdRp + helicase ORF2= structural capsid protein ORF3= small protein, function unknown 5’ 3’ ORF1 ORF2 ORF3 RdRp hel cap ? Genome:  Genome www.pubmed.gov; PMID: 13679618 www.allthevirologyonthewww.com RdRp Structure:  RdRp Structure Crystal structure from www.pubmed.gov PMID: 12706072 Replication Strategy:  Replication Strategy Replication suggested- Typical of positive-sense ss RNA viruses, unconfirmed Wagner et al. Basic Virology. www.netlibrary.com Replication of the Genome:  Replication of the Genome Wagner et al. Basic Virology. www.netlibrary.com Disease Manifestations:  Disease Manifestations Infects small intestines and causes gastroenteritis Expansion of the villi at proximal small intestine and shortening of the microvilli -epithelial cells remain intact Incubation period: 24-48 hours Mistakenly termed- “stomach flu” Path of Infection:  Path of Infection Wagner et al. Basic Virology. www.netlibrary.com Clinical Symptomology:  Clinical Symptomology Non-bloody diarrhea Nausea Vomiting Abdominal cramps Malaise Myalgias Headache Low-grade fever Symptoms last 12-60 hours. Children tend to suffer from vomiting, while adults tend to suffer from diarrhea. Transmission:  Transmission Fecal-Oral Typically in contaminated drinking water Many sources found : poorly maintained municipal supplies wells recreational lakes swimming pools cruise ship water food handled by infected person or washed with contaminated water Prevalence of Sources of Transmission:  Prevalence of Sources of Transmission Epidemiology and Incidence:  Epidemiology and Incidence Found Worldwide. Burden: - ca. 267,000,000 annual cases - 612,000 hospitalizations - 3,000 deaths Highly contagious: fewer than 100 virus particles can cause infection 2002- Cruise ship bound for Alaska- 13% of 1266 on board were affected; contaminated drinking water Epidemiology:  Epidemiology Frankenhauser et al. www.cdc.gov Slide19:  Outbreaks of Gastroenteritis Associated with Noroviruses on Cruise Ships --- United States, 2002 During January 1--December 2, 2002, CDC's Vessel Sanitation Program (VSP), which conducts surveillance for acute gastroenteritis (AGE) on cruise ships with foreign itineraries sailing into U.S. ports (1), received reports of 21 outbreaks of AGE* on 17 cruise ships. Of the 21 outbreaks, nine were confirmed by laboratory analysis of stool specimens from affected persons to be associated with noroviruses, three were attributable to bacterial agents, and nine were of unknown etiology. Seven outbreaks were reported in 2001, and of these, four were confirmed to be associated with norovirus (CDC, unpublished data, 2002). This report describes five of the norovirus outbreaks that occurred during July 1--December 2, 2002, on cruise ships. Outbreaks Cruise Ship A. On July 18, cruise ship A, owned by cruise line A, embarked 1,318 passengers and 564 crew members for a 7-day cruise from Vancouver to Alaska. On July 19, five passengers reported to the ship's infirmary with symptoms of AGE (Figure 1). By July 25, a total of 167 (13%) passengers and nine (2%) crew members had reported illness. Among the 176 patients, the predominant symptoms were vomiting (76%) and diarrhea (73%). Five of 10 stool specimens from ill passengers were positive for norovirus by reverse transcriptase polymerase chain reaction (RT-PCR). On July 25, when passengers disembarked, the ship was disinfected in accordance with CDC recommendations, and the same day, a new group of passengers embarked for another 7-day cruise. During the cruise, 189 (14%) of 1,336 passengers and 30 (5.3%) of 571 crew members had AGE with diarrhea (91%) and vomiting (85%) (Figure 1). An environmental health inspection conducted by CDC revealed no sanitary deficiencies. Cruise line A cancelled a subsequent cruise and voluntarily took the ship out of service for 1 week for aggressive cleaning and sanitizing. No outbreaks were reported on subsequent cruises. Cruise Ship B. On October 1, cruise ship B, also owned by cruise line A, embarked 1,281 passengers and 598 crew members for a 21-day cruise from Washington to Florida. By October 16, a total of 101 (8%) passengers and 14 (2%) crew members reported to the infirmary with AGE symptoms. On October 18, CDC investigators boarded the ship to conduct an epidemiologic and environmental investigation. Of 972 surveyed passengers, 399 (41%) met the case definition for AGE. Investigators found no association between illness and water, specific meals served on the ship, or with offshore excursions. Stool specimens from 12 of 13 patients tested positive for norovirus. Characterization of the strain by sequence analysis of RT-PCR products matched those from cruise ship A. Despite implementation of control measures that included disinfection of the vessel and quarantine of ill passengers and crew members, a total of 264 passengers and 41 crew members reported illness on three subsequent 10-day cruises. Cruise line A voluntarily withdrew cruise ship B from service for 10 days for aggressive cleaning and sanitizing. No outbreaks were reported on subsequent voyages. Cruise Ship C. On September 28, cruise ship C, owned by cruise line B, embarked 1,984 passengers and 941 crew members for a 7-day round-trip cruise from Florida to the Caribbean. Several passengers had AGE within 24 hours of embarkation, and by October 1, a total of 70 (4%) passengers and two (0.2%) crew members reported illness. On October 3, CDC investigators boarded the ship to conduct an epidemiologic and environmental investigation. Questionnaires completed by 1,879 (95%) passengers and 860 (91%) crew members identified 356 (19%) passengers and 13 (1.5%) crew members who met the AGE case definition. The epidemiologic investigation suggested a point source of infection, followed by cases associated with person-to-person transmission. The investigation identified an association between illness among passengers and lunch served at embarkation (odds ratio=2.4; 95% confidence interval=1.1--5.2; p value=0.02). Four of 11 stool specimens from patients were positive for norovirus by RT-PCR. Characterization of the strain by sequence analysis of RT-PCR products matched those from an outbreak on the same ship that occurred 3 weeks previously but was not identical to the outbreak strain on cruise ships A and B. CDC recommended reinforcing sanitation practices and excluding ill foodhandlers from the work place. Cruise ship C continued service, and no new cases were reported on subsequent cruises. Reported by: EH Cramer, MD, D Forney, Vessel Sanitation Program; AL Dannenberg, MD, Div of Emergency and Environmental Health Svcs, National Center for Environmental Health; MA Widdowson, VetMB, JS Bresee, MD, S Monroe, PhD, RS Beard, H White, MS, S Bulens, MPH, Div of Viral and Rickettsial Diseases; E Mintz, MD, C Stover, MPH, Div of Bacterial Diseases, National Center of Infectious Diseases; E Isakbaeva, MD, J Mullins, DVM, J Wright, DVM, V Hsu, MD, W Chege, MD, J Varma, MD, EIS officers, CDC. Prevention and Control:  Prevention and Control Highly Stable in environment- resistant to: freezing heating to 60ºC disinfection w/ chlorine acidic conditions vinegar alcohol high sugar concentration Prevention and Control:  Prevention and Control Infection produces IgG, IgA and IgM, but antibodies are not protective. No lasting immunity or protection from reinfection. Transient immunity- lasting 3-4 months. Vaccine not likely. No current antiviral drugs, however complete recovery is most common. Prevent by hand-washing, good hygiene, proper water management, preparation of food. Things to Remember for Exam:  Things to Remember for Exam Defining structural characteristic(s). Nucleic acid/ genome type. How many open reading frames and what each one contains (general). Cell tropism and effects; hint- Does Norwalk virus kill intestinal epithelial cells? Infectious dose; environmental stability Lasting immunity?; protective antibodies produced? References:  References Centers for Disease Control and Prevention. “Norwalk-Like Viruses:” Public health consequences and outbreak management. MMWR 2001; 50 (No. RR-9): [inclusive page numbers]. www.cdc.gov - MMWR, 2003, Outbreaks on Cruise ships. www.pubmed.gov suggested articles, PMID: 13679618; 14499247; 14557646; 14715308; 12791850; 12706072 Wagner, E.K.; Martinez, H. Basic Virology. Malden, MA. Blackwell Science, 1999. www.netlibrary.com Dorlands Online Medical Dictionary. www.dorlands.com

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