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Editor – Disease control strategies and research priorities should be
informed by the wise interpretation of appropriate surveillance data(1).
The Study of Infectious Intestinal Disease in England(2) (IID Study)
demonstrated that laboratory report surveillance underestimates the number
of people infected with Norwalk-like virus (NLV). In 1995 there were an
estimated 606,700 community cases of NLV infection in England compared
with 1,926 laboratory reports received by the Public Health Laboratory
Service Communicable Disease Surveillance Centre (CDSC). However, this
estimation failed to account for the fact that environmental health
officers, consultants in communicable disease control and hospital
clinicians generate most laboratory reports of NLV through investigations
of general outbreaks of infection(3). When these investigations are
considered the ratio of illness in the population to laboratory reports
received by CDSC falls from more than 1500:1 to 315:1. This still means
that 6.4% of all IID in England resulted from NLV infection and, clearly,
NLV caused more IID than any other recognised pathogen. However the IID
study also demonstrated that NLV infection is comparatively mild. Only
16% of those infected with NLV presented to general practice, compared
with 32% for rotavirus, 47% for campylobacter and 73% for salmonella.
Since the symptoms of NLV infection are usually mild and short-lived
the main purpose of surveillance in England & Wales is to indicate the
impact of NLV beyond individual case reports using systematic surveillance
of general outbreaks of IID. These data show that NLV outbreaks in
hospitals are common events in winter with over 750 outbreaks recorded in
the nine year period January 1992 to December 2000(4). Although these
outbreaks can have a considerable impact on services, most affected fewer
than 20 people (range 2-522). Outbreak surveillance data were used to
inform the development of guidelines on the management of hospital
outbreaks(5)and to establish a research project examining transmission of
NLV in healthcare settings. This will include integrated epidemiological
and microbiological information. While the suggestions to improve
reporting of outbreaks and sentinel surveillance are welcomed, outbreak
surveillance in England and Wales has already identified successfully the
impact of NLV infection in healthcare settings. It has also informed the
development of control policies and research initiatives.
References
1. Cowden JM. Winter vomiting – infections due to Norwalk-like viruses
are underestimated. BMJ 2002; 324: 249-50 (2 February)
2. Food Standards Agency. A report of the study of infectious intestinal
disease in England. London: The Stationery Office, 2000.
3. Dedman D, Laurichesse H, Caul EO, Wall PG. Surveillance of small round
structured virus (SRSV) infection in England and Wales, 1990-5. Epidemiol
Infect 1998; 121: 139-49.
4. PHLS. Outbreaks of Norwalk-like virus infection. CDR Weekly [serial
online] 2002 [cited 9 February 2002]; 12(4):
5. Chadwick PR, Beards G, Brown D et al. Management of hospital outbreaks
of gastro-enteritis due to small round structured viruses. J Hosp Infect
2000; 45: 1-10.
Sarah J O’Brien, Head of Gastrointestinal Diseases Division, PHLS
Communicable Disease Surveillance Centre, 61 Colindale Avenue, LONDON NW9
5EQ.
Goutam K Adak, Consultant Epidemiologist, Gastrointestinal Diseases
Division
Benjamin A Lopman, Clinical Scientist, Gastrointestinal Diseases Division
Mark H Reacher, Consultant Epidemiologist, Gastrointestinal Diseases
Division
David WG Brown, Director, Enteric, Respiratory and Neurological Virus
Laboratory, PHLS Central Public Health Laboratory, 61 Colindale Avenue,
London NW9 5ST.
Competing interests:
No competing interests
02 March 2002
Sarah J O'Brien
Head of Gastrointestinal Diseases Division
Goutam K. Adak, Benjamin A. Lopman, Mark H. Reacher, and David W.G. Brown
PHLS Communicable Disease Surveillance Centre, 61 Colindale Avenue, London Nw9 5EQ
Winter vomiting - outbreak surveillance identifies impact in hospitals
Editor – Disease control strategies and research priorities should be
informed by the wise interpretation of appropriate surveillance data(1).
The Study of Infectious Intestinal Disease in England(2) (IID Study)
demonstrated that laboratory report surveillance underestimates the number
of people infected with Norwalk-like virus (NLV). In 1995 there were an
estimated 606,700 community cases of NLV infection in England compared
with 1,926 laboratory reports received by the Public Health Laboratory
Service Communicable Disease Surveillance Centre (CDSC). However, this
estimation failed to account for the fact that environmental health
officers, consultants in communicable disease control and hospital
clinicians generate most laboratory reports of NLV through investigations
of general outbreaks of infection(3). When these investigations are
considered the ratio of illness in the population to laboratory reports
received by CDSC falls from more than 1500:1 to 315:1. This still means
that 6.4% of all IID in England resulted from NLV infection and, clearly,
NLV caused more IID than any other recognised pathogen. However the IID
study also demonstrated that NLV infection is comparatively mild. Only
16% of those infected with NLV presented to general practice, compared
with 32% for rotavirus, 47% for campylobacter and 73% for salmonella.
Since the symptoms of NLV infection are usually mild and short-lived
the main purpose of surveillance in England & Wales is to indicate the
impact of NLV beyond individual case reports using systematic surveillance
of general outbreaks of IID. These data show that NLV outbreaks in
hospitals are common events in winter with over 750 outbreaks recorded in
the nine year period January 1992 to December 2000(4). Although these
outbreaks can have a considerable impact on services, most affected fewer
than 20 people (range 2-522). Outbreak surveillance data were used to
inform the development of guidelines on the management of hospital
outbreaks(5)and to establish a research project examining transmission of
NLV in healthcare settings. This will include integrated epidemiological
and microbiological information. While the suggestions to improve
reporting of outbreaks and sentinel surveillance are welcomed, outbreak
surveillance in England and Wales has already identified successfully the
impact of NLV infection in healthcare settings. It has also informed the
development of control policies and research initiatives.
References
1. Cowden JM. Winter vomiting – infections due to Norwalk-like viruses
are underestimated. BMJ 2002; 324: 249-50 (2 February)
2. Food Standards Agency. A report of the study of infectious intestinal
disease in England. London: The Stationery Office, 2000.
3. Dedman D, Laurichesse H, Caul EO, Wall PG. Surveillance of small round
structured virus (SRSV) infection in England and Wales, 1990-5. Epidemiol
Infect 1998; 121: 139-49.
4. PHLS. Outbreaks of Norwalk-like virus infection. CDR Weekly [serial
online] 2002 [cited 9 February 2002]; 12(4):
5. Chadwick PR, Beards G, Brown D et al. Management of hospital outbreaks
of gastro-enteritis due to small round structured viruses. J Hosp Infect
2000; 45: 1-10.
Sarah J O’Brien, Head of Gastrointestinal Diseases Division, PHLS
Communicable Disease Surveillance Centre, 61 Colindale Avenue, LONDON NW9
5EQ.
Goutam K Adak, Consultant Epidemiologist, Gastrointestinal Diseases
Division
Benjamin A Lopman, Clinical Scientist, Gastrointestinal Diseases Division
Mark H Reacher, Consultant Epidemiologist, Gastrointestinal Diseases
Division
David WG Brown, Director, Enteric, Respiratory and Neurological Virus
Laboratory, PHLS Central Public Health Laboratory, 61 Colindale Avenue,
London NW9 5ST.
Competing interests: No competing interests