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Noroviruses. Niv Seerpi & Mark Sears Green River District Health Department. Introducing the artiste formerly known as NLV. Noroviruses (genus Noroviruses, family Caliciviridae) are a group of related RNA viruses that cause acute gastroenteritis in humans

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Niv Seerpi & Mark Sears

Green River District Health Department

introducing the artiste formerly known as nlv
Introducing the artiste formerly known as NLV
  • Noroviruses (genus Noroviruses, family Caliciviridae) are a group of related RNA viruses that cause acute gastroenteritis in humans
  • These viruses were formerly known as “Norwalk-like viruses”
  • Were also referred to as Caliciviruses, and as Small Round Structured Viruses, or SRSVs
  • Named after the original strain which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968
  • Currently, there are atleast five norovirus genogroups (GI, GII, GIII, GIV & GV) which in turn are divided into at least 31 genetic clusters
clinical presentation
Clinical Presentation
  • Incubation period – 24 to 48 hrs, can be as short as 12 hrs
  • Acute onset vomiting, watery non-bloody diarrhea, abdominal cramps, nausea, low-grade fever
  • Symptoms usually short-lived, 24-60 hours
  • Complete recovery with no long-term sequelae
  • Fecal-oral route, either by consumption of fecally contaminated food or water or direct person-to-person spread
  • Environmental & fomite transmission
  • Aerosolization of vomitus results in droplets that contaminate surfaces or may enter the oral mucosa


  • Highly contagious
  • Shedding usually begins with onset of symptoms and may continue for 2 weeks after
  • Immunity is strain-specific and lasts only a few months
  • Due to genetic variability of noroviruses, individuals are likely to be repeatedly infected throughout their life-times
disease burden
Disease Burden
  • CDC estimates that 23 million cases of acute gastroenteritis that occur annually are due to norovirus infection
  • At least 50% of all food-borne outbreaks can be attributed to noroviruses
  • Contamination of food by a food handler immediately before it’s consumption
  • Usually associated with consumption of cold foods like salads, sandwiches, and bakery products
  • Other foods implicated include oysters, and produce like raspberries
  • Sewage contamination of wells & recreational water have led to community outbreaks
  • Use of Reverse Transcriptase Polymerase Chain Reaction
  • Identification of virus from stool specimens taken 48-72 hours after onset
  • Older methods include electron microscopy, and detection of four-fold increase of specific antibodies in acute & convalescent phase blood samples
  • Sequencing of noroviruses helps by linking cases to each other in Epi investigations
  • Sequences are entered into CaliciNet – a database used to store the different sequences of noroviruses
  • Symptomatic therapy to replace fluid loss & correct electrolyte disturbances through oral and IV fluid administration
noroviruses in congregate settings
Noroviruses in congregate settings
  • Noroviruses can spread rapidly in congregate living conditions
  • Nursing Homes
  • Schools
  • Cruise ships
in the green river district
In the Green River District
  • 4 outbreaks of Norovirus in nursing homes in the past 4 months
  • 1 outbreak on a steamboat cruise on the Ohio River
what is the health departments role in an outbreak
What is the Health Departments role in an outbreak?
  • Confirm existence of an outbreak
  • Define case
  • Data collection
  • Coordinate collection of lab specimens & their submission
  • Institute disease control & prevention measures
  • Active surveillance measures
  • Determine when an outbreak is over
  • Enhanced surveillance post-outbreak
  • Data analysis
  • Communicate findings
it all began on a friday afternoon
It all began….on a Friday afternoon
  • On Friday October 20, 2006, at 3.00 pm the GRDHD Epidemiologist was contacted by the ICN at Henderson Methodist Hospital
  • She relayed information that a steamboat with sick passengers was docking at Henderson later that day
  • The hospital was asked to prepare to treat these patients
  • Details about the numbers and the nature of illness were not available
conference call
Conference Call
  • A few minutes later, Dr Thoroughman called to ask us to participate in a conference call pertaining to illness on board the Mississippi Queen
  • The Mississippi Queen had started this cruise on October 18 in Cincinnati, OH, and was scheduled to dock at Louisville, Henderson, Paducah, Cape Girardeau, MO, and conclude in St. Louis, MO on the October 25.
  • Staff from the Kentucky DPH, Cincinnati DPH, West Virginia DPH, CDC & FDA participated in the call
conference call cont
Conference Call (cont)
  • A clearer picture of the symptomology was presented; although details about numbers affected were sketchy
  • It was then decided that Niv Seerpi, Epidemiologist and Mark Sears, Environmental Director would meet the boat at the Henderson riverfront and accompany the boat from Henderson to Paducah, which was their next stop
  • A six member CDC team was to join us in Paducah
cdc involvement
CDC Involvement
  • Later that evening we were contacted by Anandi Sheth, MD, the CDC officer who was heading the investigation
  • She faxed the Passenger Questionnaire - the survey instrument that was to be administered to all passengers & crew on board
mississippi queen
Mississippi Queen
  • We boarded the boat at 8:30 pm that evening
  • We spoke with the crew members and made arrangements for the questionnaires to be handed out
  • We also made preliminary recommendations regarding infection control & disinfection
  • We also examined the vessel’s gastrointestinal illness log
and we are on our way
And we are on our way….
  • The boat was to depart for Paducah at noon on the 21st of October
  • A representative of the US Food & Drug Administration joined us at the Henderson riverfront and accompanied us on the trip from Henderson to Paducah
  • On October 20-21, 34 passengers were treated at Methodist Hospital in Henderson for symptoms of nausea, diarrhea and dehydration
  • Stool specimens were collected from 8 hospitalized passengers
  • Three passengers were treated at Owensboro Medical Health System
  • Other passengers who were not ill but wished to leave the boat were provided lodging at a hotel in Evansville, IN
  • Outbreak control measures observed:
    • Hand sanitizers were strategically placed
    • All sheets were washed in water >180 degrees F
    • All blankets were replaced with new, all bedspreads were removed for dry-cleaning
    • A private cleaning contractor was brought on board to wipe down all hard surfaces using phenolic-based cleaner
    • Public restrooms were closed
    • No self-service at the luncheon/dinner buffets
  • During the trip from Henderson to Paducah, the GRDHD and FDA Staff checked the water supply, food handling practices, general sanitation procedures and disease control procedures aboard the boat
  • In addition, we gathered information from the passengers and crew to try to pinpoint a common source of contamination
  • We obtained completed surveys from 390 of 512 (76%) passengers and crew onboard
cdc team arrives
CDC Team arrives…
  • The investigation was turned over to the CDC Epi Investigation Team and the staff of the Purchase District Health Department at the Paducah Riverfront
  • As some of the ill passengers were taken to an area hospital as well as local hotels, the Purchase District Health Department checked for secondary cases and educated hotel staff on disease control precautions
  • Similar practices were instituted at the hotels in Evansville, IN
cruise discontinued
Cruise discontinued
  • This cruise was cancelled at its Cape Girardeau, MO stop and all remaining passengers were transported by bus to the final destination of St. Louis, MO due to continued illness onboard
  • A total of 156 passengers (42%) and 16 crew (11%) reported illness on this cruise
  • CDC Labs confirmed the presence of GII Noroviruses in stool specimens that were collected at different stops along the way – Henderson, Paducah & Cape Girardeau
investigation continues
Investigation continues
  • Despite a thorough cleaning and sanitization supervised by the CDC and the FDA, another outbreak occurred on the next cruise, and this cruise was discontinued after only 3 days
  • The CDC and the FDA continue to investigate these outbreaks of noroviruses aboard the Mississippi Queen