Measles, rubella and mumps virus CNR

The National Reference Centers ( CNR ) are expert laboratories in the microbiology of communicable diseases . They are appointed by order of the Ministry responsible for health for a period of 4 years. CNR Committee placed under the responsibility of the Director General of the Institute for Health Monitoring.

It is responsible, in close liaison with Public Health France (SpF), for contributing to the diagnosis and epidemiological surveillance of human infections caused by the measles virus (Measles virus, MeV, measles virus), human respiratory syncytial virus (hRSV , RSV ), human metapneumovirus (hMPV), the 4 human parainfluenza viruses (hPIV) and mumps virus (MuV, mumps virus).

The virological diagnosis of measles generally accompanies the process of “DO” (Compulsory Notification of Measles). It is based either on direct diagnosis: testing for the virus or its constituents (RNA, antigens), or on testing for antibodies: indirect diagnosis or serodiagnosis.

Withdrawals :

• The saliva sample is taken by the doctor using a saliva kit provided by the ARS , comprising the systems for sampling (“salivette”), transport (box and envelope), and information (clinical identity). The sample allows the search for the viral RNA genome and anti-virus antibodies in the event of negative RNA. It is sent by post to the CNR .
• In a hospital setting, a nasal or nasopharyngeal sample on virological transport medium is recommended. It allows to search for viral RNA.
• The blood sample is most often intended for the search for anti-measles virus antibodies (serology). This is the recommended approach in community medicine today (Cf. Recommendations sheet). The peripheral blood sample is taken from a dry tube. It is not necessary if a saliva sample has been taken. The presence of the virus in the blood (viremia) can be tested on an EDTA blood tube.
• In certain complications, other samples are useful: tracheo-bronchial secretions, urine, cerebrospinal fluid, etc.

The techniques :

• The basic technique used for the detection of the virus is the search for the viral RNA by a molecular technique: RT- PCR (reverse-transcription, polymerase-chain-reaction) in real time. In the event of positive detection, the identification of the viral genotype is carried out by sequencing part of the viral genome.
• The isolation of measles virus strains is carried out at the CNR on Vero Slam cell cultures. It is indicated for the study of certain viral strains.
• The detection of anti-measles virus antibodies, of the IgG and IgM classes, is carried out routinely using commercial immunoenzymatic kits (ELISA). The search for neutralizing antibodies in cell culture (protective antibodies) is possible, but more complicated. From a certain level, they are correlated with the levels of antibodies detected in ELISA.

Response times, interpretation and transmission of results:

• Viral RNA is detectable in about 4-5 hours by the RT- PCR . It signs the current viral infection. In the saliva or the nasopharynx, it is present during the invasive and eruptive phases. Detection in the blood (viremia) is early and transient. The presence of the virus in the urine can be prolonged for a few days.
• The isolation of the virus in culture requires at least one week of culture.
• Anti-measles virus antibodies can be assayed in ELISA in approximately 2 hours. The presence of IgM and IgG antibodies indicates infection (apart from recent anti-measles vaccination). IgM and IgG antibodies appear with the rash; IgM persist for about 2 months, and IgG for a very long time…
• CNR for more than 72 hours at room temperature may cause the detection tests for RNA, virus or IgM antibodies to be falsely negative.

The results of the examinations carried out at the CNR are immediately transmitted to the prescribing doctor or biologist, who, within the framework of the DO, must transmit them to the local ARS

For all viruses ( RSV , hMPV, hPIV, MuV, NDV), the recommended sample is a collection of nasal secretions:

• They are taken by a swab supported from the anterior part of the nasal fossae or by aspiration using a pump. They must be placed in a specific medium (virological transport medium) and sent to the CNR .
•   Other samples can be used: tracheo-bronchial secretions in intubated patients, CSF: mumps.
• RSV infections (there is no viremia and specific antibodies appear delayed). It is useful in mumps: detection of IgM and IgG by ELISA in case of primary infection.

    The techniques used for direct research:

• The detection of RSV , hMPV and hPIV1,2 and 3 antigens is carried out by immunofluorescence on a smear of nasal secretions.
• Viral isolation is possible on MRC5 cells for RSV , and on certain continuous human or animal lines for hPIV, hMPV and MuV. This technique is not recommended for diagnosis.
• The search for viral RNA is carried out by RT- PCR for all viruses: RSV , hPIV, hMPV, MuV, NDV. real-time or conventional, uni- or multiplex RT- PCR

    Response times, interpretation and transmission of results:

• The direct immunofluorescence test provides a result in about 60 min. It may appear negative if the sample was taken late, if it contains few cells, or was transmitted in poor conditions.
• Viral RNA is detectable in about 4-5 hours by the RT- PCR , and 24 hours by the classic PCR It signs the current viral infection. For all viruses, it is always present during the acute phase of the disease and can persist for several days after recovery.

The results of the examinations carried out at the CNR are sent directly to the prescribing doctor or biologist.

• The CNR contributes to knowledge of seroprevalence and the level of protection of the population against measles, mumps, RSV , hHMPV, hPIV and NDV viruses through serological surveys.
• The CNR ensures the epidemiological tracing of infections linked to these different viruses occurring in communities (identification of the index case, nosocomial epidemics in hospital departments, epidemics in communities of the elderly, etc.) through the use of specific molecular tools .
• The CNR compiles and maintains a strain library comprising reference strains, strains representative of successive epidemics and strains isolated from serious or specific pathologies.

• The CNR maintains and distributes biological reference material: viral strains, cell lines, positive RNA controls.
• It invests in the development, evaluation and dissemination of diagnostic techniques, commercial or academic.
• He participates in university and hospital teaching on measles, mumps, RSV , hMPV and hPIV viruses.
• It contributes to the training of foreign biologists by hosting them for internships or by involving the transfer of technologies.

The CNR is one of the European laboratories accredited for the diagnosis of measles “Euro Measles/Rubella laboratory Network”, by the WHO .

The CNR has established regular collaboration with three structures:

• InVS : bi-monthly sending of epidemiological information: number of strains, genotypes.
• “European Regional Reference laboratory for Measles and rubella” , at the Institute of Immunology (Luxembourg): sending viral sequences for comparison with other European genotypes.
• “WHO Regional Office for Europe, Communicable Disease Unit” in Copenhagen: sending epidemiological information.

The CNR , located in the Laboratory of Human and Molecular Virology of the Caen Normandy University Hospital, is open Monday to Friday from 8 a.m. to 5 p.m. Samples can be received on Saturday morning from 8:00 a.m. to 12:00 p.m.

Viral RNA searches are performed every working day.

The sheet accompanying the sample must include, in addition to the administrative information (surname, first name, age, sex, etc.) , the following information:

• the name, address, telephone number and email of the prescribing doctor,
• the date of the start of the eruption and the date of the saliva sample,
• an overall assessment of the intensity of the disease: typical measles, attenuated measles, complicated measles,
• the fragile terrain: infants, pregnant women, immunocompromised,
• the notion of a vaccination in childhood (1 or 2 doses) or recent (1 to 4 weeks), or a recent trip,
• the existence or not of grouped cases and/or an identified contact,
• the result can be expected within 24-48h. following receipt of the sample. It is immediately sent by fax or e-mail to the prescribing doctor or laboratory. A postal dispatch, including the viral genotype in the event of a positive RNA search, follows a few days later,
• the identification of the viral genotype by sequencing is carried out twice a week.