Noroviruses

Niv Seerpi & Mark SearsGreen 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

These viruses were formerly known as “Norwalk-like viruses”

Were also referred to as Caliciviruses, and as Small Round Structured Viruses, or SRSVs

Noroviruses

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

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

Transmission

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

Immunity

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

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

Outbreaks

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

Diagnosis

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

Diagnosis

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

Management

Symptomatic therapy to replace fluid loss & correct electrolyte disturbances through oral and IV fluid administration

Noroviruses in congregate settings

Noroviruses can spread rapidly in congregate living conditions

- Nursing Homes- Schools- Cruise ships

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? 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

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 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)

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

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

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….

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

Passengers 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

Measures

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

Inspection 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…

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 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

Epi Curve-MQ

0

10

20

30

40

50

Date of onset

No. o

f cas

es

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

Questions??

THANK YOU!!!