Norovirus Activity New Hampshire, 2006-2007

1. Norovirus Activity New Hampshire, 2006-2007 Beth Daly, MPH Communicable Disease Epidemiologist Communicable Disease Surveillance Section NHICEP Meeting March 13, 2007 NH Department of Health and Human Services Division of Public Health Services

2. Viral Gastroenteritis • Several viruses cause gastroenteritis • rotavirus, noroviruses, adenoviruses, sapoviruses, and astroviruses • Symptoms are often similar among etiologies, often unable to distinguish clinically • CDC: each year 23 million cases of acute gastroenteritis are due to norovirus infection • At least 50% of all foodborne outbreaks of gastroenteritis can be attributed to noroviruses NH Department of Health and Human Services Division of Public Health Services

3. Norovirus • Genus name of a group of of related, single-stranded RNA, nonenveloped viruses • Member of the Caliciviridae family which includes four viral genera: • Lagovirus, Vesivirus, Sapovirus, Norovirus • Only sapovirus and norovirus can infect humans • Previously known as “Norwalk-like Viruses” • Norwalk virus is just one type of virus in the Norovirus genus • Norwalk virus named for original strain which caused an outbreak in Norwalk, Ohio in 1968 NH Department of Health and Human Services Division of Public Health Services

4. Norovirus Genogroups • There are five norovirus genogroups (divided into at least 31 genetic clusters) • Only 3 of these genogroups can infect humans (GI, GII, GIV) • Genogroup GI: Norwalk virus, Southampton virus, Desert Shield virus • Genogroup GII: Hawaii virus, Snow Mountain agent, Toronto virus (GII/3) • Genogroup GIV: Ft. Lauderdale virus NH Department of Health and Human Services Division of Public Health Services

5. Clinical Presentation • Incubation period: 24-48 hours • median in outbreaks 36 hours • Acute-onset: • vomiting, watery non-bloody diarrhea, abdominal cramps, nausea • Symptoms may vary based on genogroup • Dehydration most common complication • Results in reversible lesions in jejunum • precise mechanism diarrhea and vomiting unknown • Symptoms last 24 to 60 hours • Recovery is complete and no evidence of serious long-term effects • Asymptomatic in 30% of infections • role in transmission unknown NH Department of Health and Human Services Division of Public Health Services

6. HANDS FOOD ES H2O AIR Transmission • Humans only known reservoir • Some noroviruses present in swine, cattle, and mice, but these genogroups do not infect humans • Transmitted primarily fecal-oral • consumption of contaminated food/water • direct person-to-person spread • Environmental/fomite contamination • Good evidence exists for transmission due to aerosolization of vomitus • droplets contaminating surfaces or entering oral mucosa and swallowed • Multiple routes seen in outbreaks NH Department of Health and Human Services Division of Public Health Services

7. Transmission • Highly infectious • As few as 10 viral particles may be sufficient for infection • Viral shedding usually begins with onset of symptoms • Presymptomatic shedding may occur • Shedding may continue for 2 weeks after recovery • Unclear to what extent viral shedding 72 hours after recovery signifies continued infectivity NH Department of Health and Human Services Division of Public Health Services

8. MMWR 2001; 50: RR-9 NH Department of Health and Human Services Division of Public Health Services

9. Immunity • Immunity may be strain-specific • lasts only a few months • individuals are likely to be repeatedly infected throughout their lifetimes. • Antibodies to the virus are noted initially in young children ages 3 to 4 • Antibody prevalence exceeds 50% by age 50 NH Department of Health and Human Services Division of Public Health Services

10. Immunity and Blood Type • Susceptibility to infection may be genetically determined • People with blood group O at greatest risk for severe infection • Noroviruses bind to several histo-blood group antigens and different genogroups have differing affinity for ABO antigens • GI noroviruses preferentially recognize blood group antigens A and O • GII noroviruses preferentially recognize blood group antigens A and B NH Department of Health and Human Services Division of Public Health Services

11. Diagnosis • RT-PCR detects norovirus RNA • can be used to test stool and emesis samples • NH PHL requests stool • Identification of virus can be best made from stool taken within 48 to 72 hours after onset • good results can be obtained on samples taken as long as 5 days after onset • Virus can sometimes be found in stool samples taken 2 weeks after recovery NH Department of Health and Human Services Division of Public Health Services

12. Epidemiology • CDC estimates 23 million cases of norovirus each year in US • In NH, norovirus is not reportable • Outbreaks are reportable • What defines an outbreak? • Transmission within the facility? • Higher than normal number of cases? NH Department of Health and Human Services Division of Public Health Services

13. Reported Outbreaks of Viral Gastroenteritis, 2002-2007 NH Department of Health and Human Services Division of Public Health Services

14. Reported Outbreaks of Viral Gastroenteritis, 2002-2007 NH Department of Health and Human Services Division of Public Health Services

15. 2006-2007 Norovirus Season • Between December 1st-March 1st • 64 outbreaks of norovirus/norovirus-like illness in institutional settings • 55 (86%) in longterm care facilities • 4 (6%) in acute care hospitals • 5 (8%) in schools • 50 (78%) outbreaks submitted stool specimens • 25 (39%) met CDC criteria for a confirmed norovirus outbreak (≥ 2 positive specimens) • 18 (28%) had one positive stool specimen • Increase seen across the United States • CDC believes increase due to new strain NH Department of Health and Human Services Division of Public Health Services

16. Control- Public Health • Notify the NH DHHS Disease Control Section immediately if you suspect an outbreak in your facility • Follow NH DHHS Guidelines for Control of GI Outbreaks in Institutional Settings • Collect stool specimens • Be sure to label lab requisition form with the word “OUTBREAK” and your Facility Name • Also helpful if you could write name of NH DHHS public health nurse you’re working with NH Department of Health and Human Services Division of Public Health Services

17. Control- Patient/Resident • Stop all group activities • Consider alternate ways of feeding the ill to prevent them from dining in common areas • Restrict/defer admission to affected areas for two incubation periods after last case • Notify visitors and encourage handwashing during/after visits NH Department of Health and Human Services Division of Public Health Services

18. Control- Staffing Issues • Staff with GI symptoms should remain out of work until 48 hours after symptom resolution • Exclude non-essential staff from affected areas • Interrupt movement of inter-department staff if possible • Staff should frequently wash hands using soap and water during suspect norovirus outbreaks • Use gloves and aprons whenever contacting an affected individual or contaminated environment NH Department of Health and Human Services Division of Public Health Services

19. Control- Environmental • Noroviruses resistant to environmental challenge • they are able to survive freezing • temperatures as high as 60°C • and have even been associated with illness after being steamed in shellfish • can survive in up to 10 ppm chlorine well in excess of levels routinely present in public water systems • CDC recommends cleaning surfaces with 1000 ppm household bleach • equivalent to 5 tablespoons per gallon • Can other cleaners be used? NH Department of Health and Human Services Division of Public Health Services

20. Nucleic acid genome (DNA or RNA) Protein shell (capsid) Lipid-protein envelope 20-300 nanometers diameter What about Alcohol Based Hand Sanitizers? • Attacks protein envelope of the virus • Noroviruses are non-enveloped! NH Department of Health and Human Services Division of Public Health Services

21. Thank you! Questions/Comments? Contact NH DHHS to report suspect outbreaks and to receive disease control recommendations and support Office: 271-4496 After Hours: 800-852-3345 ext. 5300 NH Department of Health and Human Services Division of Public Health Services