Introduction
In this paper we describe the first measles confirmed (and imported) case of 2016. This patient was exposed to measles in Pakistan, a country where measles is still endemic. We describe investigation and control measures, highlighting the importance of vigilant surveillance and proactive public health intervention during the ‘elimination’ phase of measles in Ireland.
Background
Measles is an important vaccine preventable illness with the potential for severe complications including pneumonia, encephalitis and death [1-3]. Control measures should take cognisance of an increasingly globalised world and the ongoing threat of measles introduction through travel and migration. The risk of further transmission following an importation depends on the level of immunity in the exposed population and the responsiveness of public health agencies once a case is identified[1]. Globally, estimated deaths due to measles fell by 74% between 2000 and 2010. Reduction in measles mortality accounted for 23% of the estimated decline in all-cause mortality in children under 5 years of age from 1990 to 2008 [4].The epidemiology of measles in the post-vaccination era varies across Europe and depends on the evolution of the vaccine strategy in the respective countries.
Measles is a highly contagious acute viral illness caused by a paramyxovirus and presents with fever, rash and respiratory symptoms [1, 5]. The incubation period of measles, from exposure to prodrome, averages 10-12 days. The measles virus is readily transmitted by respiratory droplets and aerosols from infected individuals from four days before rash onset (i.e. before they realize that they have measles) until four days after rash onset. Direct face-to-face contact is not necessary for transmission because respiratory droplets suspended in the air can cause infection up to two hours after a person with measles occupied a closed area (e.g. GP office) [3]. Oral fluid samples (obtained using an ORACOL swab, available from the National Virus Reference Laboratory (NVRL)) can be used for the detection of measles RNA and/or measles IgM. RNA can be detected for approximately five days following rash onset whereas IgM may be observed in specimens collected after 5 days. The detection of viral RNA allows for genotyping of the virus, thereby discriminating between endemic, imported or vaccine derived measles infection [2, 3].
In Ireland, measles became a notifiable disease in 1948[6]. In 1985, the year that the measles vaccine was introduced, there were 9,903 cases reported[6]. This figure dropped to 135 cases by 1991. The MMR vaccine, introduced in 1988[6], is provided free of charge in Ireland under the childhood immunisation programme [7]. An MMR catch up campaign started in the academic year 2012/2013 and continued during the academic year 2013/2014 during which the HSE offered a dose of MMR vaccine to children/students who had not completed (or were not sure that they had) their two doses MMR vaccination schedule[8]. Uptake of the HSE administered preschool MMR dose in 2014 was 92% [3]. Three major outbreaks in Ireland occurred in: 1989 (1,248 cases), 1993 (4,328 cases) and 2000 (1,603 cases) [6].
Due to progress in control and improved two dose MMR vaccination coverage the risk of indigenous measles occurring in Ireland is now lower than ever before. However the risk of importation of measles from high endemicity countries or regions is of concern and pockets of measles susceptibility among the child and young adult population exist. An increasing proportion of Irish measles notifications are now imported or linked to imported measles cases. In 2013, two siblings developed measles soon after returning to Ireland from Scotland [7]. In that same year, two other measles cases were imported from England and Wales respectively; in 2014 two (unrelated) cases were due to recent travel from the Philippines and one from Japan; in 2015 one measles case was related to travel from Indonesia, and led to onward transmission to a hospitality sector hotel worker in Ireland.
Index case
Notification
On 25th Feb 2016, the Department of Public Health, HSE-East received a laboratory notification of a confirmed case of measles (genotype B3) in an infant resident in Dublin city centre. On receipt of the notification, Public Health immediately investigated and established the child’s whereabouts during the infectious period. An Outbreak Control Team (OCT) was convened with representatives from the Department of Public Health HSE-East, the Health Protection Surveillance Centre (HPSC) and the NVRL to plan the investigation and implement control measures.
Investigation
The OCT established that between 29th November and 13th February 2016 the infant had traveled with his mother to Pakistan where high levels of endemic measles have been reported. The child developed a fever and coryza on 18th February 2016, five days following return to Ireland. A rash developed on 21st February 2016. The history indicated that the infant was likely to have been infected with measles abroad and was not infectious while on the return flight to Ireland. Following onset of illness, the infant attended a city-centre GP surgery on 20th and 23rd February 2016, where the case was in the waiting room for one and ten minutes respectively. Three pregnant women were included among those exposed, one of whom had received the measles vaccine as a child and none of thel three could recollect having had measles.
On 20th February 2016, the family attended a social event with ten other families including young children. Between the families and attending staff, 21 adults and 13 children were exposed to the index case. Once this group had left the premises, nobody else was in the premises for at least two and a half hours. One of these families had also visited the index case’s house for several hours earlier that day with their young infant.
On 21st February, 2016 the index case also attended a Dublin paediatric hospital Emergency Department and was present there for 10 minutes prior to isolation in a side room.
Other investigation revealed that the child was an only child who lived in a single family home, did not attend crèche or child care, had little exposure to non-household contacts other than those identified above, and when travelling to the GP or hospital at the infectious period travelled in a private car.
In summary, during the infectious period, approximately 100 contacts were identified with relevant exposure to the index case; three of whom were pregnant; none were immunocompromised.
Control measures
Based on individual risk assessments, the control measures used to prevent onward transmission included:
- Recommendation for immunoglobulin where appropriate (n=1)
- Individualized MMR vaccination advice (10 advised 2 MMRs, 8 advised 1 MMR, 2 infants advised MMR before aged 12 months)
- Recommendation for home isolation and institution of daily Public Health surveillance (see details below) of most susceptible children who may have been incubating disease:
- 1 unvaccinated child of less than 6 months of age
- 2 infants between 6 and 12 months of age who received their 1st MMR at the advice of Public Health
- 2 children received MMR as part of their routine MMR schedule within two weeks of exposure
- Advice to antenatal contacts including information regarding the signs and symptoms of measles and advice to inform their antenatal teams regarding their possible exposure to measles
- “Warn and Inform” letters sent to at-risk contacts including information about their possible exposure to measles, information about measles and advice if household members became symptomatic
- Alerts to hospital Emergency Departments (both adult and paediatric) and GPs in the Dublin region including the GP out of hours services that a measles case had been identified in Dublin and that children with unrecognised exposure might present to clinicians and should be notified immediately
Contacts were also informed that if they became symptomatic they should phone their GP/Emergency Department for advice, inform the clinician of their recent exposure and not attend unless requested to do so when appropriate infection control precautions were in place. The GPs of all social contacts were informed by phone and in writing of the MMR vaccination requirements of their patients.
Outcome
The index case recovered and there were no reported secondary cases of measles.
Discussion
The public health response to this case of imported measles comprised 1) prompt investigation, 2) communication and 3) surveillance. These three prongs of the response are discussed below.
Understanding the demographic, social, occupational and geographic characteristics of at-risk contacts are key to planning and implementing control measures. Given the highly infectious nature of measles gathering information on the vaccination status of contacts (children and adults) enabled the provision of individualised recommendations to contacts.
Public health doctors phoned the most at-risk contacts to collect additional information, advise appropriate actions in the event that they or a family member became unwell and provide recommendations about immunisation. Subsequently, this information was reiterated by letter. The OCT also communicated with the GP services of contacts (via phone and letter) to advise GPs on timely vaccinations where appropriate. Families with children who were either unvaccinated or incompletely vaccinated at the time of exposure were contacted daily via text message to document any symptoms of measles.
The OCT worked with the GP practice and hospital Emergency Department (that the index case had attended) to ensure that at-risk contacts were provided information. This included ‘Warn and Inform’ letters being sent to GP patients and Emergency Department patients as well as follow-up with any patients who had been in the Emergency Department at the time but had subsequently been admitted to the hospital. The GP service also spoke with patients considered most at-risk of measles. At-risk contacts were advised to self-isolate as much as possible, including avoiding birthday parties, having visitors or going to public places during the timeframe in which they might be incubating the virus.
Subsequent to this case of imported measles, there were no reported secondary cases. Public health advice includes that all children should receive MMR as per the immunisation schedule (at 12 months and 4-5 years). Parents travelling with children aged 6-11 months to countries where measles outbreaks are reported are recommended to discuss MMR vaccination for their children with their GPs prior to travel[9].
Measles still poses an important public health threat, even in industrialised countries with high levels of immunisation. In London there has been over 60 cases of measles recently reported over a two month period. The importance of promoting age appropriate vaccinations and facilitating immunisation for susceptible contacts of measles cases, cannot be overstated.
Conclusion
The public health response to one case of imported measles was considerable and included work carried out by Public Health, Primary Care, paediatric hospital, laboratory, surveillance and administrative staff. Consequently, this represented a substantial cost in resources and opportunity costs. However, these costs can be justified by the infectious nature of measles and the potential for onward spread, especially in young children.
Greg Martin1, Fionnuala Cooney1 (chair), Niamh Byrne1, Fiona Cianci1, Jeff Connell2, Suzanne Cotter3, Phil Downes1, Ronan Glynn1, Noelle O’Loughlin1, Mary Ward1.
1. Department of Public Health HSE-East, 2. National Virus Reference Laboratory, 3. HPSC
Acknowledgements
The Outbreak Control Team would like to extend their appreciation to the close contacts of the case for their assistance and co-operation with the team’s recommendations. We would also like to thank the GPs, Emergency Department and Hospital Infection Control personnel as well as the administration staff in the Dept of Public Health HSE-East for their work and support to the OCT.
References
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2. Heymann, D., Control of Communicable Disease Manual. 19 ed. 2008, Washington, DC: American Public Health Association.
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4. Durrheim, D.N., N.S. Crowcroft, and P.M. Strebel, Measles - The epidemiology of elimination. Vaccine, 2014. 32(51): p. 6880-3.
5. Hawker J., et al., Communicable Disease Control and Health Protection Handbook. 2012, Wiley-Balckwell.
6. O'Flanagan, D., et al., Eliminating measles and rubella and preventing congenital rubella infections. 2007: Ireland.
7. Cooney, F., et al., Family measles outbreak demonstrates effectiveness of MMR in preventing further spread in childcare facility. Epi-Insight, 2015. 16(1).
8. HPSC, Measles - Annual Epidemiological Report 2014. 2015, Health Protection Surveilance Centre.
9. WHO. International Travel and Health. 2016 [cited 2016 22 April 2016]; Available from: http://www.who.int/ith/vaccines/measles/en/.
