1 / 40

Norovirus 2007

Objectives. To describe the viral characteristics that make norovirus unique and so hard to controlTo describe the early clinical criteria used to determine that an outbreak may be occurringTo describe practical interventions to limit spread. Norovirus. Also known as

matt
Download Presentation

Norovirus 2007

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Norovirus 2007 Dr. Vivian Belmusto, MD, FAAP, DTM&H Communicable Disease Controller Sacramento County

    2. Objectives To describe the viral characteristics that make norovirus unique and so hard to control To describe the early clinical criteria used to determine that an outbreak may be occurring To describe practical interventions to limit spread

    3. Norovirus Also known as “stomach or abdominal influenza”, winter vomiting disease, vomiting bug, cruise ship virus, and (in the words of Dr. John Rosenberg) “California Nursing Home Virus” Due to time constraints, this discussion will be limited to the aspects of norovirus most pertinent to LTCFs; I will not discuss norovirus infections on cruise ships or go into foodborne transmission of norovirus infections in any great depth.Due to time constraints, this discussion will be limited to the aspects of norovirus most pertinent to LTCFs; I will not discuss norovirus infections on cruise ships or go into foodborne transmission of norovirus infections in any great depth.

    4. Norovirus Smooth round structured virus (SRSV), Norwalk-like virus (NLV), Human calicivirus (HCV), Norovirus (NV) NLVs are divided into 3 distinct genogroups: GI, GII, and GIII (GI and GII infect humans) Norovirus cannot be cultured and recommendations for the management of infections are largely based on studies that use Feline Calicivirus as a surrogate agent In 1969 there was an outbreak of “winter vomiting disease” in Norwalk Ohio. Two years later, Dolin et al described an infectious agent isolated from frozen clinical specimens from that 1969 outbreak. In 1972 Dolin further characterized this infectious agent using electron microscopy as a small, round, structured virus. In 1990, Estes et al deciphered the Norwalk virus genome as a Calicivirus. Stool detection by PCR was accomplished in 1992, and genotyping was accomplished in 1995.In 1969 there was an outbreak of “winter vomiting disease” in Norwalk Ohio. Two years later, Dolin et al described an infectious agent isolated from frozen clinical specimens from that 1969 outbreak. In 1972 Dolin further characterized this infectious agent using electron microscopy as a small, round, structured virus. In 1990, Estes et al deciphered the Norwalk virus genome as a Calicivirus. Stool detection by PCR was accomplished in 1992, and genotyping was accomplished in 1995.

    5. Genotype Surveillance 1998-2004 GII-4 predominate in nursing home and hospital outbreaks but are rare in oyster- and water-related outbreaks despite continuous circulation in the population GI strains are detected in the majority of environmental outbreaks

    6. Genotype Surveillance Several strains are frequently found in oyster- and water-linked outbreaks (up to seven), whereas one single strain was detected when transmission was person-to-person GII predominate in sporadic cases while GI strains are more frequent in outbreaks Bon et al. J Clin Microbiol. 2005 September; 43(9): 4659-4664.

    8. Norovirus Characteristics

    9. Slide courtesy of John Rosenberg, MD. This is probably the most important slide in the presentation in terms of understanding what makes norovirus so unique and efficient in producing disease. NV can be transmitted through food, water, air, person to person, and environmental surfaces.Slide courtesy of John Rosenberg, MD. This is probably the most important slide in the presentation in terms of understanding what makes norovirus so unique and efficient in producing disease. NV can be transmitted through food, water, air, person to person, and environmental surfaces.

    10. Pathophysiology of Norovirus Enteritis of the proximal small intestine and mucosal lesions of the villous epithelium Colon and stomach are spared (histopathology) Delayed gastric emptying during the acute illness Produces transient (up to 2 weeks duration) D-xylose malabsorption Only 60% of people become symptomatic!Only 60% of people become symptomatic!

    11. Clinical Characteristics Excretion of virus in stool begins a few hours before the onset of symptoms and a maximum of 24-72 hours after exposure Symptoms usually last 24-60 h; 30% of infections may be asymptomatic Virus can be present in stool of infected persons for a week or more after recovery or even if never sick

    12. Volunteer Studies NV was administered orally to 50 volunteers: Viral shedding (antigen) first appeared at 15 h, peak 25-72 h, lasts >7 days* 41/50 (82%) were infected 34 (68%) symptomatic (24 diarrhea, 16 vomiting) 18 (32%) asymptomatic Graham et al. JID 1994; 170:34-43 NV cannot be cultured, therefore all studies are based on antigen shedding and PCR. It is not known whether the antigen is truly part of the infectious complex. Fully 1/3 of volunteers were asymptomatic No protection conferred from pre-existing antibody; presence of antibody seemed to correlate with increased symptoms On heme-onc wards, shedding has been shown for up to 140 days.NV cannot be cultured, therefore all studies are based on antigen shedding and PCR. It is not known whether the antigen is truly part of the infectious complex. Fully 1/3 of volunteers were asymptomatic No protection conferred from pre-existing antibody; presence of antibody seemed to correlate with increased symptoms On heme-onc wards, shedding has been shown for up to 140 days.

    13. Norovirus Susceptibility and Resistance Susceptibility to norovirus is related to histo-blood group antigens (HBGAs) status: NV attach to carbohydrates of the histo-blood group family on human gastroduodenal epithelial cells (and saliva) if present Affinity may vary by viral genotype Human milk contains decoy receptors Oysters contain similar receptors Slide courtesy of John Rosenberg, MD

    14. In one study by Hutson et al, ABO secretor genotype was determined from archived serum samples; in a study of 50 volunteers, all 8 non-secretors were resistant to infection, while all 42 infected volunteers were secretor positive. In other words, norovirus appears to target A and O secretors. Slide courtesy of John Rosenberg.In one study by Hutson et al, ABO secretor genotype was determined from archived serum samples; in a study of 50 volunteers, all 8 non-secretors were resistant to infection, while all 42 infected volunteers were secretor positive. In other words, norovirus appears to target A and O secretors. Slide courtesy of John Rosenberg.

    15. Attack Rates and Blood Types 400/722 students infected through food contamination: Blood Group A: 71.1% (133/187) Blood Group AB: 55.3% (26/47) Secondary Attack rate: Overall: 38% (109/283) Blood Group A: 41.4% (55/133) Blood Group O: 39.5% (49/124) Blood Group AB: 19.2% (5/26) Miyoshi et al. Kansenshogaku Zasshi. 2005 Sep;79:664-71

    16. Frequency of Secondary (Household) Transmission of Gastroenteritis 19% of HH contacts of 121 persons swimming at a recreational lake Baron et al. AJE 1982 Nov;116:163-172 29% of HH contacts of 103 students and teachers at an elementary school Kappus et al. AJE 1982 Nov 116:834-9 14% of HH contacts of 195 attendees of daycare centers Gotz et al. Scand J Infect Dis. 2002;34(2):115-21 Obviously this is quite significant when we consider the risk of infection to health care and direct patient care workers by their family members and other contacts. In a case-control study by Fretz et al., 39% of individuals reported contact with an ill person prior to the onset of their symptoms and 33% reported contact with ill persons after illness. Slide courtesy of John Rosenberg, MD.Obviously this is quite significant when we consider the risk of infection to health care and direct patient care workers by their family members and other contacts. In a case-control study by Fretz et al., 39% of individuals reported contact with an ill person prior to the onset of their symptoms and 33% reported contact with ill persons after illness. Slide courtesy of John Rosenberg, MD.

    17. Factors Associated with Secondary AGE Among Household Contacts Age of Contact; transmission inversely proportional to age of contact (<2yrs 4 times more likely to transmit infection) Bed sharing Exposure to primary vomiting episode Member of index family Perry et al. EID Vol. 11, No. 7, July 2005 These factors are based on a study done on 936 predominantly Hispanic household in Northern California. Among 3,916 contacts of 1,099 primary case patients, the secondary attack rate was 8.8%.These factors are based on a study done on 936 predominantly Hispanic household in Northern California. Among 3,916 contacts of 1,099 primary case patients, the secondary attack rate was 8.8%.

    18. Children and Norovirus Children < 1 year of age are less likely to experience vomiting, while the 4-10 year old age range has the highest incidence of vomiting Children < 1 year of age were proportionately more likely to still be shedding virus at 8, 15, and 22 days compared with other age groups. Rockx et al. Clinical Infectious Diseases 2002;35:246-253

    19. Courtesy of John RosenbergCourtesy of John Rosenberg

    20. Slide courtesy of John Rosenberg.Slide courtesy of John Rosenberg.

    22. Epidemiology and Transmission of NV in Healthcare Settings In healthcare spread primarily through hand contamination of those who are ill* Vomiting results in viral particles suspended in the air and producing environmental contamination NV can remain infectious on environmental surfaces for many days and a relatively resistant to disinfection *Ill healthcare workers dispensing medications have been responsible for transmission in some outbreaks.*Ill healthcare workers dispensing medications have been responsible for transmission in some outbreaks.

    23. For all reported norovirus median 11 days , range 1-73 longest in schools and mental correctional facility For all reported norovirus median 11 days , range 1-73 longest in schools and mental correctional facility

    24. The Kaplan Criteria for Identification of Norovirus Outbreaks Vomiting in more than half of affected persons Mean (or median) incubation period 24-48 hr Mean (or median) duration of illness 12-60 hr No bacterial pathogen in stool culture* Turcios et al. Clinical Infectious Diseases 2006; 42::964–9 An outbreak of AGE should be suspected when 2 or more residents or staff have onset of vomiting (often projectile) or diarrhea within 1-2 days. Enteric cultures are not necessarily indicated when we have clinical illness compatible with viral gastroenteritis, and certainly, institutions should never await the results of stool testing before implementing control measures in a suspected outbreakAn outbreak of AGE should be suspected when 2 or more residents or staff have onset of vomiting (often projectile) or diarrhea within 1-2 days. Enteric cultures are not necessarily indicated when we have clinical illness compatible with viral gastroenteritis, and certainly, institutions should never await the results of stool testing before implementing control measures in a suspected outbreak

    25. Recommendations Maintain active surveillance for outbreaks of gastroenteritis Rapid interruption of person to person transmission!* Implement guidelines when initial cases are suspected (Extent of outbreaks can be limited if transmission prevention precautions are implemented when the first 2-3 cases are suspected) * There is probably little that can be done to prevent the initial introduction of the virus, since an infected healthcare worker or visitor may be shedding the virus even before they are ill, or may never be symptomatic.* There is probably little that can be done to prevent the initial introduction of the virus, since an infected healthcare worker or visitor may be shedding the virus even before they are ill, or may never be symptomatic.

    26. DHS Recommendations October 2006 Nursing units should immediately report patients or staff with sudden onset of symptoms suggestive of AGE to ICP or Director of Nursing New cases of staff and patients should be recorded daily using a case log Notify the medical director, the Licensing and Certification district office with jurisdiction over your facility, AND the LHD

    27. DHS Recommendations Confine symptomatic patients to their rooms until 48 h after symptoms cease Request symptomatic staff to stay at home until asymptomatic for at least 24 h (48? 72?)* Request symptomatic family members to avoid visitation * There is some debate as to how long staff should remain at home after symptoms cease. Recognizing the burden that staff shortages pose to facilities and to staff who may not be compensated for sick time, as well as recognizing that individuals may shed virus asymptomatically or shed for longer periods of time after symptoms have resolved (2 weeks), DHS has recommended a minimum amount of 24 h between the cessation of symptoms. A staff illness policy outlining the requirements for exclusion and the circumstances for returning to work should be developed and employees should be educated about the policy. Strict hand hygiene should be stressed to all employees including those returning from illness.* There is some debate as to how long staff should remain at home after symptoms cease. Recognizing the burden that staff shortages pose to facilities and to staff who may not be compensated for sick time, as well as recognizing that individuals may shed virus asymptomatically or shed for longer periods of time after symptoms have resolved (2 weeks), DHS has recommended a minimum amount of 24 h between the cessation of symptoms. A staff illness policy outlining the requirements for exclusion and the circumstances for returning to work should be developed and employees should be educated about the policy. Strict hand hygiene should be stressed to all employees including those returning from illness.

    28. Staff Recommendations Avoid floating staff from affected to unaffected units and maintain same staff assignments Exclude nonessential personnel from affected units In addition to standard precautions, wear gloves, gowns, and surgical or procedure masks when in contact with symptomatic residents* *Gowns, gloves, and masks should be changed between contacts with roommates and removed before leaving the contaminated environment. Hands should be washed before leaving the environment and care should be taken not to touch or brush against any potentially contaminated surfaces. Also, staff should be reminded to change their clothing prior to going to assignments in other facilities. Staff should also be reminded not to work in other direct patient care settings if they have been excluded in one due to illness.*Gowns, gloves, and masks should be changed between contacts with roommates and removed before leaving the contaminated environment. Hands should be washed before leaving the environment and care should be taken not to touch or brush against any potentially contaminated surfaces. Also, staff should be reminded to change their clothing prior to going to assignments in other facilities. Staff should also be reminded not to work in other direct patient care settings if they have been excluded in one due to illness.

    29. Handwashing Remove gloves, then gown, then perform hand hygiene, then remove mask. If gloves or hands are visibly soiled, wash hands with soap and water. Alcohol hand gels may be used if there is no visible soiling. Most prudent may be to always wash hands with soap and water and then apply alcohol-based gels even if there is no visible soiling.

    30. Patient Recommendations Minimize movement of residents Dedicate use of medical equipment to single residents or similarly symptomatic residents Consider use of anti-emetics Cancel or postpone group activities until individuals asymptomatic for at least 48 h Asymptomatic, exposed residents should not be moved from an affected to an unaffected nursing unit since they may already be infected.Asymptomatic, exposed residents should not be moved from an affected to an unaffected nursing unit since they may already be infected.

    31. Patient Recommendations Limit new admissions until the incidence of new cases has reached zero. If new admissions are necessary, admit new residents to unaffected units or units that have had no new cases for at least 48 h

    32. Slide courtesy of John RosenbergSlide courtesy of John Rosenberg

    33. Environmental Management Promptly clean and disinfect vomit and fecal spillages Increase the frequency of routine ward cleaning, especially frequently touched surfaces such as faucet and door handles and bed rails

    34. Environmental Management Consider the use of respiratory protection for cleaning staff where aerosols may be present following vomiting or generated by cleaning activity Dry vacuuming and floor buffing are not recommended during outbreaks

    35. Environmental Management Bleach is best: 1:100 {500ppm} to 1:10 {5,000ppm} to disinfect surfaces contaminated with feces or vomitus* Clean carpets and soft furnishings with hot water and detergent or steam clean. While EPA-approved disinfectants are acceptable, bleach is considered best. Moreover, EPA-approved disinfectants are tested on Feline calicivirus and may not represent activity against norovirus. The correct preparation of chlorine solutions may be found in Appendix 2 of the state guidelines.While EPA-approved disinfectants are acceptable, bleach is considered best. Moreover, EPA-approved disinfectants are tested on Feline calicivirus and may not represent activity against norovirus. The correct preparation of chlorine solutions may be found in Appendix 2 of the state guidelines.

    36. Outbreak Investigations LHD Role When at outbreak is reported, the LHD will ask for a line list of cases including the date and time of onset and S/S for both residents and staff (updated daily) AND a diagram of the facility The LHD will usually suggest a few specimens (3?) be submitted for clinical (PCR) testing.* *This can be done free of charge through the PHL. If the clinical S/S are highly suggestive of a viral pathogen, it usually is not necessary to send specimens for enterics; on the other hand if the presentation is atypical, further testing may be indicated. A sample case log may be found in Appendix 1 of the state guidelines.*This can be done free of charge through the PHL. If the clinical S/S are highly suggestive of a viral pathogen, it usually is not necessary to send specimens for enterics; on the other hand if the presentation is atypical, further testing may be indicated. A sample case log may be found in Appendix 1 of the state guidelines.

    37. Outbreak Investigations LHD Role If needed, the LHD will provide facilities with the most recent DHS Recommendations for the Prevention and Control of Viral Gastroenteritis Outbreaks in California Long-Term Care (October 2006) and discuss the facility’s proposed control plan If requested or needed, the LHD may assist with an on site consultation to assist in outbreak management If facility personnel feel comfortable implementing control measures, we ask that we be kept up to date with the progress in containing the outbreak.If facility personnel feel comfortable implementing control measures, we ask that we be kept up to date with the progress in containing the outbreak.

    38. Outbreak Investigations LHD Role Monitor the effectiveness of control measures implemented through daily reports (good control measures should limit new daily cases to 1-2 per day, beginning 24-48 h after implementation) Continued occurrence of substantial numbers of cases 48 h or more following institution of control suggests inadequate control measures or compliance.Continued occurrence of substantial numbers of cases 48 h or more following institution of control suggests inadequate control measures or compliance.

    40. Questions? Disease Control and Epidemiology Unit 1-(916)-875-5881

More Related