The epidemiology of acute encephalitis
Julia Granerod and Natasha S. Crowcroft
Health protection agency, Centre for Infection, London, UK
Encephalitis means inflammation of the brain matter. Despite being a rare condition,
encephalitis is of public health importance worldwide because it has high morbidity
and mortality. Yet, many details about its epidemiology have yet to be elucidated.
This review attempts to summarise what is known about the epidemiology of the infective
cause of encephalitis and is based on a literature search of the Medline archives.
Infection is the most common cause identified, with viruses being the most important
known aetiological agents. Incidence varies between studies but is generally between
3.5 and 7.4 per 100,000 patient- years. Encephalitis affects people of all ages;
however, incidence is higher in the paediatric population. Although both sexes are
affected, most studies have shown a slight predominance in males. Encephalitis occurs
worldwide; some aetiologies have global distribution (herpesviruses) while others
are geographically restricted (arboviruses). Although definite epidemiological trends
are evident, it is difficult to make generalisations as few population- based studies
exist, most cases are not reported to health authorities, and many possible pathogens
are implicated but in most cases a cause is never found. A better understanding
of the epidemiology of this devastating disease will pave the way for better prevention
and control strategies.
NEUROPSYCHOLOGICAL REHABILITATION 2007,17 (4/5), 406-428
Encephalitis in early childhood
Surveillance Period: October 1998-October 2001
Investigator: Dr K N Ward, Consultant Virologist/Honorary Senior Lecturer, Dept
of Virology, University College London, Windeyer Building, 46 Cleveland St, London
W1P 6DB. Tel: 020 7679 9134 (24 hour cover) Fax: 020 7580 5896 E-mail: k.n.ward@ucl.ac.uk.
Professor E M Ross,
Professor of Community Paediatrics, Mary Sheridan Centre, Guy's, King's & St
Thomas' School of Medicine, 405 Kennington Road London SE11 4QW.
Published Papers: KN Ward, NJ Andrews, CM Verity, E Miller, Em Ross,. Encephalitis
Human herpes viruses-6 and 7 each cause significant neurological morbidity in Britain
and Ireland. Arch Dis Child. 2005;90;619-62233
www.bpsu.inopsu.com
MFPHM Submission
The Epidemiology of Encephlaitis in England and Wales
Dr A Bhan
July 1994 (Banked July 1993)
ABSTRACT
AIMS:These were to describe the epidemiology of encephalitis and to examine the
effect of measles vaccine and measles, mumps and rubella (MMR) vaccine and a number
of viruses on the incidence of encephalitis.
METHOD:Information from notifications, Public Health Laboratory data and the general
practitioners' sentinel reporting system were used to describe encephalitis in terms
of time, place and person, and in relation to certain viruses. An examination was
also made of trends in encephalitis before and after the introduction of measles
vaccine and measles, mumps and rubella (MMR) vaccine.
RESULTS:The incidence of encephalitis appears to be decreasing but seasonal and
secular trends in notification are difficult to interpret. Reductions in notified
cases of encephalitis occur at approximately the same time as the introduction of
vaccines but it is not possible to attribute any peaks of encephalitis notifications
to reports of specific viruses.
CONCLUSION:Much of the epidemiology described is speculative so the notification
system is not fulfilling one of its objectives, therefore a new system of notification
for encephalitis is proposed.
KEYWORDS Encephalitis Epidemiology Measles Mumps Vaccination
Full
Article
Review of the effect of measles vaccination on the epidemiology of SSPE
H Campbell1, N Andrews2, K E Brown3 and E Miller1,*
1Immunisation Department, Health Protection Agency Centre for Infections,
61 Colindale Avenue, London NW9 5EQ, UK.
2 Statistics Unit, Health Protection Agency Centre for Infections, 61
Colindale Avenue, London NW9 5EQ, UK.
2 Immunisation and Diagnosis Unit, Health Protection Agency Centre for
Infections, 61 Colindale Avenue, London NW9 5EQ, UK.
Abstract
Background When measles vaccines were widely introduced in the 1970s, there were
concerns that they might cause subacute sclerosing panencephalitis (SSPE): a very
rare, late-onset, neurological complication of natural measles infection. Therefore,
SSPE registries and routine measles immunization were established in many countries
concurrently. We conducted a comprehensive review of the impact of measles immunization
on the epidemiology of SSPE and examined epidemiological evidence on whether there
was any vaccine-associated risk.
Methods Published epidemiological data on SSPE, national SSPE incidence, measles
incidence and vaccine coverage, reports of SSPE in pregnancy or shortly post partum
were reviewed. Potential adverse relationships between measles vaccines and SSPE
were examined using available data.
Results Epidemiological data showed that successful measles immunization programmes
protect against SSPE and, consistent with virological data, that measles vaccine
virus does not cause SSPE. Measles vaccine does not: accelerate the course of SSPE;
trigger SSPE or cause SSPE in those with an established benign persistent wild measles
infection. Evidence points to wild virus causing SSPE in cases which have been immunized
and have had no known natural measles infection. Perinatal measles infection may
result in SSPE with a short onset latency and fulminant course. Such cases are very
rare. SSPE during pregnancy appears to be fulminant. Infants born to mothers with
SSPE have not been subsequently diagnosed with SSPE themselves.
Conclusions Successful measles vaccination programmes directly and indirectly protect
the population against SSPE and have the potential to eliminate SSPE through the
elimination of measles. Epidemiological and virological data suggest that measles
vaccine does not cause SSPE.
Keywords SSPE, subacute sclerosing panencephalitis, epidemiology, measles, measles
vaccine, MMR vaccine, genotype, vaccination
Accepted 6 September 2007
International Journal of Epidemiology 2007 36(6):1334-1348; doi:10.1093/ije/dym207
Infections of the central nervous system of suspected viral origin: A collaborative
study from Finland
Marjaleena Koskiniemi, Timo Rantalaiho, Heli Piiparinen, Carl-Henrik von Bonsdorff,
Markus Färkkilä, Asko Järvinen, Esko Kinnunen, Suvi Koskiniemi, Laura
Mannonen, Marketta Muttilainen, Kimmo Linnavuori, Jukka Porras, Mirja Puolakkainen,
Kirsti Räiha, Eeva-Marjatta Salonen, Pentti Ukkonen, Antti Vaheri, Ville Valtonen,
and the Study Group
The Haartman Institute, Department of Virology, University of Helsinki; and Helsinki
University Central Hospital, Helsinki, Finland
We studied 3231 patients with acute central nervous system (CNS) symptoms of suspected
viral origin to elucidate the current etiologic spectrum. In 46% of the cases, a
viral finding was observed. Varicella –zoster virus (VZV) was the main agent
associated with encephalitis, as well as meningitis and myelitis. VZV comprised
29% of all confirmed or probable etiologic agents. Herpes simplex virus (HSV) and
enterviruses accounted 11% each, and influenza A virus 7%. VZV seems to have achieved
a major role in viral infections of CNS. In encephalitis in our population, VZV
is clearly more commonly associated with these neurological diseases than HSV. The
increase in VZV findings may in part be a Pseudophenomenon due to improved diagnostic
methods, however, a true increase may have occurred and the pathogenic mechanisms
behind this should be elucidated. Journal of NeuroVirology (2001), 400-408.
Keywords: encephalitis, myelitis, meningitis, central nervous system; viral
infection; neurological infection
Journal of NeuroVirology , Volume 7
Neurologic Disorders After Measles-Mumps-Rubella Vaccination
Annamari Mäkelä, MD*, J. Pekka Nuorti, MD and Heikki Peltola, MD*
Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki,
Finland
Department of Infectious Disease Epidemiology, National Public Health Institute,
Helsinki, Finland
Objective. The possibility of adverse neurologic events has fueled much concern
about the safety of measles-mumps-rubella (MMR) vaccinations. The available evidence
concerning several of the postulated complications is controversial. The aim of
this study was to assess whether an association prevails between MMR vaccination
and encephalitis, aseptic meningitis, and autism.
Methods. A retrospective study based on linkage of individual MMR vaccination
data with a hospital discharge register was conducted among 535 544 1- to 7-year-old
children who were vaccinated between November 1982 and June 1986 in Finland. For
encephalitis and aseptic meningitis, the numbers of events observed within a 3-month
risk interval after vaccination were compared with the expected numbers estimated
on the basis of occurrence of encephalitis and aseptic meningitis during the subsequent
3-month intervals. Changes in the overall number of hospitalizations for autism
after vaccination throughout the study period were searched for. In addition, hospitalizations
because of inflammatory bowel diseases were checked for the children with autism.
Results. Of the 535 544 children who were vaccinated, 199 were hospitalized
for encephalitis, 161 for aseptic meningitis, and 352 for autistic disorders. In
9 children with encephalitis and 10 with meningitis, the disease developed within
3 months of vaccination, revealing no increased occurrence within this designated
risk period. We detected no clustering of hospitalizations for autism after vaccination.
None of the autistic children made hospital visits for inflammatory bowel diseases.
Conclusions. We did not identify any association between MMR vaccination
and encephalitis, aseptic meningitis, or autism.
Key Words: measles • mumps • rubella • MMR vaccine •
immunization • adverse ef-fects • encephalitis • aseptic meningitis
• autism • autistic dis-orders
Abbreviations: MMR, measles-mumps-rubella • MIBE, measles inclusion body
encephalitis • SSPE, subacute sclerosing panencephalitis • CSF, cerebrospinal
fluid • ICD, International Classification of Diseases
PEDIATRICS Vol. 110 No. 5 November 2002, pp. 957-963
Received for publication Jun 3, 2002; Accepted Jul 25, 2002