Laboratory Surveillance of Measles and Rubella in Norway
Published: 10.11.05 Updated: 05.12.2005 10:35:30
D.H. Skutlaberg 1, K. Vainio 1, Oe. Loevoll 2
1 Department of Airborne Infections at the Norwegian Institute of Public Health (NIPH), 2 Department of Infectious Disease Epidemiology at NIPH
Between 1961 and 1970, nationwide rubella epidemics were observed every 4-5 years in Norway. From 1984 to 2001, six cases of congenital rubella syndrome were registered. During the same period, almost 197,000 cases of measles were reported. Immunisation against measles and rubella was introduced in 1969 and 1978, respectively. As a result of the immunization, the incidence of both infections declined. Measles vaccination coverage was 84% in 2003. Since 2000, only imported cases or cases linked to imported cases (last case in 2002), have been reported. Laboratory analyses include antibody analysis, detection of viral nucleic acid and molecular characterization. In the case of an outbreak of febrile-rash illness, samples from at least 5-10 cases are analysed for antibodies. Reference service is provided by the WHO collaborating National Measles and Rubella Laboratory at the Norwegian Institute of Public Health.
According to the Strategic Plan for Measles and Congenital Rubella Infection in the European Region of WHO, the objectives are to interrupt the indigenous transmission of measles, and to prevent congenital rubella infection (CRI) (< 1 case per 100 000 live births) in Europe by 2010 (1). Meeting these objectives requires a very low level of susceptibility to measles throughout the population and to rubella among women of childbearing age.
Before the introduction of immunization against measles in 1969 and rubella in 1978 these infections were very common in Norway. Nation-wide epidemics of rubella were observed every 4-5 years and almost 197 000 cases of measles, including 30 fatalities, were reported between 1961 and 1970 (2). The incidence of both diseases declined gradually as a result of immunization, and since 2000 only 0 8 cases of measles (imported or linked to an imported case) and 0 4 cases of rubella have been reported annually (2). Six cases of CRI have been reported during 1984-2001, and the last case in Norway was an imported infection in 2002 (3). In 2004 Norway had a population of 4.6 million and approximately 56 000 live births (4).
According to official reported figures for 2003, the vaccination coverage for measles and rubella in Norway is 84% (5) with a variation among 2-year old children from 78 - 92% (6) in the 19 counties. The overall coverage in Norway is low compared to countries in Baltic area and other Nordic countries that report 93% - 99% coverage of measles vaccine (5). The vaccination coverage in Norway is considerably lower than 95% as recommended by WHO to prevent sustained virus transmission of measles following an importation (1).
Epidemics in unvaccinated groups, as have been described in other countries in Europe (7), may also happen in Norway. To be able to respond to this, rapid reporting and investigation of every suspected case of measles and rubella as well as all detected clusters of febrile-rash illness is necessary. Both diseases are notifiable and are to be reported through an early warning system in Norway. Laboratory investigation should include both specimens for analyses of antibodies and specimens for detection of viral nucleic acid. Molecular characterization of virus isolates can be used to determine the origin of imported viruses as well as to differentiate between true outbreak and a cluster of unrelated imported cases. Investigating outbreaks and clusters of febrile-rash illness should at least include specimens for analyses of antibodies from 5-10 cases.
In Norway analyses to detect antibodies against measles and rubella in serum is performed at several medical microbiological laboratories throughout the country. Selected specimens, including all sera positive for measles or rubella IgM, are sent for confirmation at the WHO National Measles and Rubella Laboratory at the Norwegian Institute of Public Health (NIPH). As a member partner of the Enhanced Laboratory Surveillance of Measles (ELSM), a project that aims to develop, harmonise and co-ordinate the wider use of oral fluid based diagnostic methods and to apply these to the surveillance of measles in Europe (8), NIPH performs analyses to detect measles antibodies in oral fluid. Analyses to detect and characterize measles and rubella nucleic acid in appropriate specimens are also performed here.
In 2004 specimens from 46 suspected measles or rubella cases were analyzed at the NIPH WHO National Measles and Rubella Laboratory. This included primary analyses as well as confirmation testing. In addition to diagnosing actual cases, the laboratory also performs serological surveys to assess susceptibility for measles and rubella in the population.
In order to provide epidemiological evidence for the low incidence of measles and rubella in Norway, data from all laboratories performing measles and rubella diagnostics are collected by NIPH. These data, which include the number of cases with possible disease investigated and the result of the analyses, is reported monthly to WHO through the centralized information system for infectious diseases (CISID) (9).
1. The Strategic Plan for Measles and Congenital Rubella Infection in the European Region of WHO, Copenhagen, WHO Regional Office for Europe, 2003 (http://www.euro.who.int/document/e81567.pdf)
2. The Norwegian Surveillance System for Communicable Diseases (MSIS), Norwegian Institute of Public Health (http://www.msis.no)
3. Tilfelle av medfdt rubella. MSIS. Norwegian Institute of Public Health. MSIS-rapport 2002; 30 (41).[In Norwegian, accessed 1 March 2005] Available from: http://www.fhi.no/davx/nyhetsbrev/msis/2002/41/msis.pdf
4. Statistisk sentralbyr (www.ssb.no)
5. WHO-UNICEF coverage estimates (www.who.int/vaccines-surveillance/StatsAndGraphs.htm)
6. The Norwegian surveillance program for vaccination coverage (SYSVAK) (http://www.fhi.no/tema/vaksine/dekning)
7. Experts raise alarm over measles in Europe. Bull World Health Organ. [online]. Nov. 2004, vol.82, no.11 [cited 01 March 2005], p.890-890. Available from: http://www.scielosp.org/scielo.php?script=sci_arttext&pid=S0042-96862004001100022&lng=en&nrm=iso ISSN 0042-9686.
8. Enhanced Laboratory Surveillance of Measles (ELSM) (http://www.elsm.net/)
9. CISID home-page (http://data.euro.who.int/cisid)