Overview

Measles, a highly infectious disease with frequent complications, can be eliminated. The World Health Organization (WHO) is encouraging all countries to improve measles elimination activities. The increased availability of oral fluid sample kits in Irish hospitals will assist in more rapidly confirming the diagnosis and in discarding non-measles cases. In this report we highlight progress in measles control in Ireland and increased emphasis on virus identification and genotyping using oral fluid samples. 

The measles virus is readily transmitted by respiratory droplets and aerosols from infected individuals to those who are non-immune. People with measles can transmit the virus from four days before rash onset (before they realise that they have measles) until four days after rash onset. Direct face-to-face contact is not needed for transmission to occur as airborne transmission via very small respiratory droplets suspended in the air can occur up to two hours after a person with measles occupied a closed area (eg GP office).

The disease caused by the virus presents as a fever-rash illness, typically characterised by a high temperature, fever, cough, runny nose (coryza) and conjunctivitis. Approximately 30% of all measles cases report one or more complications eg otitis media, diarrhoea, pneumonia and encephalitis. Complications are more common in children less than 5 years of age and adults 20 years of age and older.

Vaccination with a measles containing vaccine, such as the Measles-Mumps-Rubella (MMR) vaccine, has been used in Ireland since 1988 to prevent infection. Two doses are recommended, at 12 months and 4-5 years of age. Most recent MMR uptake data (first dose of MMR) for children at 24 months of age indicates that 93% of children are getting the first dose (Q2 2015). The uptake of the HSE administered preschool MMR dose in 2014 was 92% (2013-2014 vaccination report).

As a result of improved uptake of MMR among young children and older children and teenagers (as part of MMR catch-up campaigns) the numbers of measles notifications has decreased markedly in recent years, making the goal of measles elimination within our horizon. Ten measles notifications have been reported in 2015 (provisional data as of 23/11/2015). This is a marked decline from the 403 measles cases reported in 2010 (Figure 1). 

Figure 1. Measles notifications 2009-2015 (as of 24/11/2015)

Diagnosis of measles

In recent years both serum and oral fluid have been used to diagnose measles. Oral fluid sample tests have particular advantages over serum samples in that oral fluid samples can be used for parallel testing for both serological (IgM) and molecular (RNA) evidence of infection. As false positive IgM result can occur, the identification of viral RNA is becoming increasingly important to confirm measles or rubella infection. RNA can be detected for at least the first 5 days following rash onset, and often prior to the development of specific IgM. Furthermore, the detection of viral RNA allows the virus to be genotyped, thereby discriminating between endemic and imported infections. 

Of note, genotyping of all laboratory measles and rubella cases is now recommended by WHO in order to identify importation of disease and monitor transmission in Europe. 

Summary

As Ireland progresses towards measles elimination, comprehensive and rapid investigation of all suspected cases will underpin the success of measles elimination activities. In order to improve the diagnosis of measles cases HPSC and National Virus Reference Laboratory (NVRL) are recommending that all hospitals increase the availability of oral fluid swabs as part of the diagnostic work up of all suspected measles cases. Oral fluid swabs (ORACOL) can be obtained from NVRL.  

As NVRL is accredited by WHO as a national laboratory for measles and rubella diagnosis, all hospital laboratories doing measles diagnostic testing are required to submit all positive samples and a selection of negative samples to NVRL as part of a quality assurance programme for measles surveillance and to ensure that genotyping of the measles virus can be done. Further detail on testing and sample collection is located in the NVRL user manual.

Recommendations for investigation of all suspected cases

• All suspectedmeasles cases should:
  • be isolated immediately to prevent possible transmission
  • be investigated and samples obtained for laboratory testing to confirm or out-rule measles
  • have samples obtained upon first clinical consultation or as soon as possible after this
  • Patients seen in GP setting should ideally have a serum sample obtained at the time of clinical presentation. The local Department of Public Health should be contacted as soon as possible in order that they can send out an oral fluid swab for the patient and commence investigation. The swab may be sent to the GP or to the patient (dependent on the region)
  • Patients seen in the hospital setting where oral fluid swabs are increasingly available, should have both oral fluid swab and a serum sample taken at the time of clinical presentation. Clinicians should notify the local Department of Public Health as soon as possible in order that case investigation can commence and preventive measures put in place.

Specimen collection

Further details on specimen collection are available on the NVRL website. 

Please note that when sending samples from patients with suspected measles or rubella for laboratory testing, the date of rash onset, recent vaccination history, and recent exposure history are vital to allow accurate interpretation of the laboratory results.

Virology diagnostic request forms used by the NVRL
1.       General serology 
2.       Oral fluid investigations

Suzanne Cotter, HPSC