Biological
Closed. Please see Biological100
HPSC outlines latest norovirus trends
http://ndsc.newsweaver.ie/epiinsight/epq9pqq0uzsqldxs0g4hal?a=1&p=31757905&t=17517774
Cited
Background
Norovirus is one of the leading global causes of gastroenteritis. Noroviruses lead to particular problems in environments where people congregate when infection can be rapidly transmitted by both faecal and vomitus routes. Since greater congregation occurs in winter, this increased proximity promotes the dissemination of norovirus leading to extensive outbreaks in congregate settings. Accordingly, outbreaks occur in hospitals, nursing and residential homes, childcare facilities, schools, hotels, cruise ships and places of employment, potentially leading to massive disruption to care or business continuity, substantial economic loss, and, occasionally, mortality in vulnerable patient populations. It is very unusual that norovirus is directly responsible for the death of patients; rather it is as a complicating factor in an already compromised patient that norovirus poses the greatest risk. It is in patients whose vital reserves are low, that noroviral illness is most likely to become a terminal factor.
Noroviruses that produce human disease are divided into two main genogroups which between them contain approximately 25 genotypes. Since 1995, a single genotype, Genogroup II genotype 4 (GII.4) has been the dominant strain of norovirus detected worldwide and in Ireland since 2002.1,2 Noroviruses, because they are readily genetically mutable, produce only short term (and often partial) immunity with consequent capacity to reinfect an individual after only a short period of time (probably as little as three months). In addition, it would appear that some individuals with a certain genetic profiles appear to have innate resistance to infection, which may account for the apparently discriminatory nature of human infection during outbreaks.
Noroviruses are very resilient being resistant to household disinfectants and low temperature washing. Inactivation of norovirus requires the use of dilute hypochlorite solution (household bleach at a concentration of 1:1000) or temperatures of at least 600C.
Epidemiology and clinical features
Noroviral illness and outbreaks became statutorily notifiable in Ireland in 2004; information on this illness has been gathered in a consistent way since then. Noroviruses produce upsurges with regularity; the most recent major upsurge was in 2002-3. During that epidemic (the most severe in recent memory) the responsible circulating strain appears to have had a novel surface antigen, effectively leaving the entire population susceptible. Conversely, the 2010-11 and 2011-12 seasons were particularly mild from the perspective of norovirus activity. The 2012-13 season has been marked, so far, by quite conspicuously elevated levels of norovirus activity.
From comparisons with international data, it can be estimated that at least one percent of the population will develop noroviral infection during low-activity seasons. During upsurge years, this figure can rise to three or even five percent. Given that the typical norovirus season lasts about 20 weeks, were between 3% and 5% of the population to be affected (the bulk being so during the high season), this would equate to between 6,600 and 11,000 people affected each week (conversely, during low seasons, this figure is likely to be about 2,000 cases per week). In one important study (Acute Gastroenteritis in Ireland, North and South. A Telephone Survey available here), published in 2003 and undertaken between December 2000 to November 2001 (which included a period of quite high norovirus activity), it was estimated that there were about 60,000 episodes of gastroenteritis each week on the island of Ireland ? equating to about 45,000 cases per week in the Republic of Ireland. This would suggest that a figure of 2,000-11,000 norovirus cases each week could well be an underestimation.
The main symptoms of noroviral infection are vomiting and, sporadically, diarrhoea but patients can develop headache, myalgia, pyrexia and abdominal pain. The vomitus from a patient with norovirus is highly infectious and any surfaces, food or water contaminated by vomit or faeces can transmit disease. The infectious dose is tiny; as few as 10 viral particles are necessary to induce gastroenteritis in a healthy adult.
The onset is sudden and the illness is generally mild (although it can be more severe in older people). The duration of the illness is normally short, rarely more than a couple of days and most people make a full and rapid recovery. Symptoms usually appear within 24-48 hours of being exposed to the virus.
Even after a patient?s vomiting or diarrhoea has stopped, they go on shedding virus at significant volumes from their body for at least 48 hours (and probably as long as one week). This is the basis for the advice that all staff in healthcare and other work settings and children in childcare and school remain off for at least 48 hours after the resolution of their symptoms, to limit onward spread of infection.
Certain groups of staff have a very high potential for spreading norovirus and this can lead to illness being passed on to vulnerable groups. These include:
?Food handlers whose work involves unwrapped or ready to eat food,
?Health care staff who have contact with food or patients,
?Those who may find it difficult to practise good personal hygiene
In addition, children aged below 5 years attending nurseries, playgroups, etc are at greater risk of contracting and spreading norovirus.
Current situation
Over the last number of years, norovirus activity has mirrored (with minor differences) the pattern seen across the rest of the northern hemisphere. The last major upsurge year was 2002-3 with minor upsurges since then (see Figure 1 below).
Figure 1: Historical norovirus activity by season: Notifications (Blue) and outbreaks (Red) ? 2004/5-2012/13
see!
http://ndsc.newsweaver.ie/epiinsight/epq9pqq0uzsqldxs0g4hal?a=1&p=31757905&t=17517774
The above figure illustrates the cyclical nature of norovirus activity and its peaking in winter (generally early in the New Year), and is based upon weekly norovirus notifications augmented by numbers of notified outbreaks. In general there is a close correlation between the weekly numbers of norovirus notifications and weekly outbreak notifications. Not all norovirus outbreaks will be confirmed as such; when such outbreaks meet a series of clinical and epidemiological criteria in the absence of microbiological confirmation, these are referred to as suspected norovirus outbreaks, but are included in the overall figures as there is a high degree of certainty that they have, in fact, a viral aetiology.
HPSC?s notification system for norovirus has, over a number of years, been calibrated to give an estimate of the level of activity, and to provide signals as to the likelihood of major (or minor) upsurges.
Norovirus activity is considered to be at a low level when there are fewer than 20 notifications per week (these levels are typical during the summer and suggest that an impending upsurge is highly unlikely). Activity is considered to be at a medium level when notifications are running between 20 and 49 per week (these levels are typical during low upsurge periods, or as a harbinger, or in the immediate aftermath of, an upsurge), while activity is considered to be at a high level when notifications exceed 50 per week. During upsurge periods levels can typically exceed 100 notifications per week.
In the last three months of 2012, 38 Community Hospitals/Long-stay unit, 31 Residential institutions and 25 Hospitals have been affected resulting in 1,956 cases of noroviral illness. Given the numbers of long stay units affected (but with the caveat that there is a surveillance bias in favour of detecting outbreaks in such settings), it is likely that a significant number of vulnerable patients have been affected; one of these patients is known to have died. The national GP sentinel system indicates that gastroenteritis levels are rising in parallel with norovirus notifications.
During 2013, there has been a marked elevation in norovirus activity. In each of the first four weeks of 2013 norovirus activity (in terms of weekly notifications) has been high; 63 in week 1, 84 in week 2, 80 in week 3 and 73 in week 4 (as of 25/01/2013).
Media alerts have been released to the General Public by the HSE. These releases have been taken up widely by the media.
Control Measures
Full information on the steps to control norovirus infection in healthcare settings are available in the HPSC guidance document: National Guidelines On The Management Of Outbreaks Of Norovirus Infection In Healthcare Settings available here.
These steps include:
?Prompt establishment of an outbreak control team that is responsible for controlling the spread of infection and coordinating the investigation of and responses to an outbreak is essential.
?Early communication and the rapid institution of early control measures
?Essential early steps in control of an outbreak will include:◦immediate cleaning and environmental decontamination of soiled areas,
◦frequent hand washing with warm water and soap for all staff and patients,
◦segregation of those who are ill from those who are not (cohorting), limitation of movement of staff and patients,
◦exclusion of ill staff from work for 48 hours after their last episode of vomiting and/or diarrhoea and
◦Sensible management of hospital visiting.
The increase in norovirus activity seen in Ireland is mirrored across the northern hemisphere. Norovirus evolves rapidly and since the mid 1990?s, new genetic variants of GII.4 have emerged and become the predominant strain on average every two to three years.
A new genetic variant of GII.4, termed Sydney 2012, was identified in association with the recent increase in norovirus outbreaks in Europe.3 As part of the surveillance of norovirus outbreaks, a selection of specimens from Irish outbreaks undergo genetic characterisation at the National Virus Reference Laboratory. Sequence and phylogenetic analysis have identified the GII.4 Sydney 2012 variant circulating across Ireland in late 2012.
Paul McKeown, Jeff Connell, Linda Dunford, Sarah Jackson, Fiona Cloak, Darina O?Flanagan
References
1. van Beek J, Ambert-Balay K, Botteldoorn N, Eden J, Fonager J, et al. (2013) Indications for worldwide increased norovirus activity associated with emergence of a new variant of genotype II.4, late 2012. Euro surveillance : bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 18.
2. Kelly S, Foley B, Dunford L, Coughlan S, Tuite G, et al. (2008) Establishment of a national database to link epidemiological and molecular data from norovirus outbreaks in Ireland. Epidemiology and infection 136: 1472-1479.
3. Waters A, Dunford L, Tuite G, Connell J, Dooley S, et al. (2008) Significant prevalence and genetic diversity of norovirus infection in Irish children. Pediatric research 64: 312-316.
:tiphat:
http://ndsc.newsweaver.ie/epiinsight/epq9pqq0uzsqldxs0g4hal?a=1&p=31757905&t=17517774
Cited
Background
Norovirus is one of the leading global causes of gastroenteritis. Noroviruses lead to particular problems in environments where people congregate when infection can be rapidly transmitted by both faecal and vomitus routes. Since greater congregation occurs in winter, this increased proximity promotes the dissemination of norovirus leading to extensive outbreaks in congregate settings. Accordingly, outbreaks occur in hospitals, nursing and residential homes, childcare facilities, schools, hotels, cruise ships and places of employment, potentially leading to massive disruption to care or business continuity, substantial economic loss, and, occasionally, mortality in vulnerable patient populations. It is very unusual that norovirus is directly responsible for the death of patients; rather it is as a complicating factor in an already compromised patient that norovirus poses the greatest risk. It is in patients whose vital reserves are low, that noroviral illness is most likely to become a terminal factor.
Noroviruses that produce human disease are divided into two main genogroups which between them contain approximately 25 genotypes. Since 1995, a single genotype, Genogroup II genotype 4 (GII.4) has been the dominant strain of norovirus detected worldwide and in Ireland since 2002.1,2 Noroviruses, because they are readily genetically mutable, produce only short term (and often partial) immunity with consequent capacity to reinfect an individual after only a short period of time (probably as little as three months). In addition, it would appear that some individuals with a certain genetic profiles appear to have innate resistance to infection, which may account for the apparently discriminatory nature of human infection during outbreaks.
Noroviruses are very resilient being resistant to household disinfectants and low temperature washing. Inactivation of norovirus requires the use of dilute hypochlorite solution (household bleach at a concentration of 1:1000) or temperatures of at least 600C.
Epidemiology and clinical features
Noroviral illness and outbreaks became statutorily notifiable in Ireland in 2004; information on this illness has been gathered in a consistent way since then. Noroviruses produce upsurges with regularity; the most recent major upsurge was in 2002-3. During that epidemic (the most severe in recent memory) the responsible circulating strain appears to have had a novel surface antigen, effectively leaving the entire population susceptible. Conversely, the 2010-11 and 2011-12 seasons were particularly mild from the perspective of norovirus activity. The 2012-13 season has been marked, so far, by quite conspicuously elevated levels of norovirus activity.
From comparisons with international data, it can be estimated that at least one percent of the population will develop noroviral infection during low-activity seasons. During upsurge years, this figure can rise to three or even five percent. Given that the typical norovirus season lasts about 20 weeks, were between 3% and 5% of the population to be affected (the bulk being so during the high season), this would equate to between 6,600 and 11,000 people affected each week (conversely, during low seasons, this figure is likely to be about 2,000 cases per week). In one important study (Acute Gastroenteritis in Ireland, North and South. A Telephone Survey available here), published in 2003 and undertaken between December 2000 to November 2001 (which included a period of quite high norovirus activity), it was estimated that there were about 60,000 episodes of gastroenteritis each week on the island of Ireland ? equating to about 45,000 cases per week in the Republic of Ireland. This would suggest that a figure of 2,000-11,000 norovirus cases each week could well be an underestimation.
The main symptoms of noroviral infection are vomiting and, sporadically, diarrhoea but patients can develop headache, myalgia, pyrexia and abdominal pain. The vomitus from a patient with norovirus is highly infectious and any surfaces, food or water contaminated by vomit or faeces can transmit disease. The infectious dose is tiny; as few as 10 viral particles are necessary to induce gastroenteritis in a healthy adult.
The onset is sudden and the illness is generally mild (although it can be more severe in older people). The duration of the illness is normally short, rarely more than a couple of days and most people make a full and rapid recovery. Symptoms usually appear within 24-48 hours of being exposed to the virus.
Even after a patient?s vomiting or diarrhoea has stopped, they go on shedding virus at significant volumes from their body for at least 48 hours (and probably as long as one week). This is the basis for the advice that all staff in healthcare and other work settings and children in childcare and school remain off for at least 48 hours after the resolution of their symptoms, to limit onward spread of infection.
Certain groups of staff have a very high potential for spreading norovirus and this can lead to illness being passed on to vulnerable groups. These include:
?Food handlers whose work involves unwrapped or ready to eat food,
?Health care staff who have contact with food or patients,
?Those who may find it difficult to practise good personal hygiene
In addition, children aged below 5 years attending nurseries, playgroups, etc are at greater risk of contracting and spreading norovirus.
Current situation
Over the last number of years, norovirus activity has mirrored (with minor differences) the pattern seen across the rest of the northern hemisphere. The last major upsurge year was 2002-3 with minor upsurges since then (see Figure 1 below).
Figure 1: Historical norovirus activity by season: Notifications (Blue) and outbreaks (Red) ? 2004/5-2012/13
see!
http://ndsc.newsweaver.ie/epiinsight/epq9pqq0uzsqldxs0g4hal?a=1&p=31757905&t=17517774
The above figure illustrates the cyclical nature of norovirus activity and its peaking in winter (generally early in the New Year), and is based upon weekly norovirus notifications augmented by numbers of notified outbreaks. In general there is a close correlation between the weekly numbers of norovirus notifications and weekly outbreak notifications. Not all norovirus outbreaks will be confirmed as such; when such outbreaks meet a series of clinical and epidemiological criteria in the absence of microbiological confirmation, these are referred to as suspected norovirus outbreaks, but are included in the overall figures as there is a high degree of certainty that they have, in fact, a viral aetiology.
HPSC?s notification system for norovirus has, over a number of years, been calibrated to give an estimate of the level of activity, and to provide signals as to the likelihood of major (or minor) upsurges.
Norovirus activity is considered to be at a low level when there are fewer than 20 notifications per week (these levels are typical during the summer and suggest that an impending upsurge is highly unlikely). Activity is considered to be at a medium level when notifications are running between 20 and 49 per week (these levels are typical during low upsurge periods, or as a harbinger, or in the immediate aftermath of, an upsurge), while activity is considered to be at a high level when notifications exceed 50 per week. During upsurge periods levels can typically exceed 100 notifications per week.
In the last three months of 2012, 38 Community Hospitals/Long-stay unit, 31 Residential institutions and 25 Hospitals have been affected resulting in 1,956 cases of noroviral illness. Given the numbers of long stay units affected (but with the caveat that there is a surveillance bias in favour of detecting outbreaks in such settings), it is likely that a significant number of vulnerable patients have been affected; one of these patients is known to have died. The national GP sentinel system indicates that gastroenteritis levels are rising in parallel with norovirus notifications.
During 2013, there has been a marked elevation in norovirus activity. In each of the first four weeks of 2013 norovirus activity (in terms of weekly notifications) has been high; 63 in week 1, 84 in week 2, 80 in week 3 and 73 in week 4 (as of 25/01/2013).
Media alerts have been released to the General Public by the HSE. These releases have been taken up widely by the media.
Control Measures
Full information on the steps to control norovirus infection in healthcare settings are available in the HPSC guidance document: National Guidelines On The Management Of Outbreaks Of Norovirus Infection In Healthcare Settings available here.
These steps include:
?Prompt establishment of an outbreak control team that is responsible for controlling the spread of infection and coordinating the investigation of and responses to an outbreak is essential.
?Early communication and the rapid institution of early control measures
?Essential early steps in control of an outbreak will include:◦immediate cleaning and environmental decontamination of soiled areas,
◦frequent hand washing with warm water and soap for all staff and patients,
◦segregation of those who are ill from those who are not (cohorting), limitation of movement of staff and patients,
◦exclusion of ill staff from work for 48 hours after their last episode of vomiting and/or diarrhoea and
◦Sensible management of hospital visiting.
The increase in norovirus activity seen in Ireland is mirrored across the northern hemisphere. Norovirus evolves rapidly and since the mid 1990?s, new genetic variants of GII.4 have emerged and become the predominant strain on average every two to three years.
A new genetic variant of GII.4, termed Sydney 2012, was identified in association with the recent increase in norovirus outbreaks in Europe.3 As part of the surveillance of norovirus outbreaks, a selection of specimens from Irish outbreaks undergo genetic characterisation at the National Virus Reference Laboratory. Sequence and phylogenetic analysis have identified the GII.4 Sydney 2012 variant circulating across Ireland in late 2012.
Paul McKeown, Jeff Connell, Linda Dunford, Sarah Jackson, Fiona Cloak, Darina O?Flanagan
References
1. van Beek J, Ambert-Balay K, Botteldoorn N, Eden J, Fonager J, et al. (2013) Indications for worldwide increased norovirus activity associated with emergence of a new variant of genotype II.4, late 2012. Euro surveillance : bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 18.
2. Kelly S, Foley B, Dunford L, Coughlan S, Tuite G, et al. (2008) Establishment of a national database to link epidemiological and molecular data from norovirus outbreaks in Ireland. Epidemiology and infection 136: 1472-1479.
3. Waters A, Dunford L, Tuite G, Connell J, Dooley S, et al. (2008) Significant prevalence and genetic diversity of norovirus infection in Irish children. Pediatric research 64: 312-316.
:tiphat: