Measles is highly infectious and can cause severe illness and occasionally cause death. Following exposure, up to 90% of susceptible people develop measles. The virus can be transmitted from four days before the rash becomes visible to four days after the rash appears.
Measles cases in this outbreak were first notified in HSE-East in early February 2011. There was a gradual increase in notifications through the summer months. However, from early August (week 31) there was a marked increase in the weekly notification of cases, to a maximum of 23 cases notified in one week in late August (Figure 1).
Figure 1. Measles cases notified in HSE-E between week 1 and week 42, 2011. (N=229)
By the end week 42, of 265 cases reported nationally 227 (86%) were from HSE-E.
The majority of these cases, 139 (61%) were reported during August and September (weeks 32-41) from the north city areas of Community Care Areas 6, 7 and 8 (Figure 2) ( Dublin northwest, Dublin north central and Dublin north respectively). This large increase in cases was primarily due to a cluster of measles in school age children in a residential summer camp in north Dublin which subsequently spread in the north inner city and Ballymun areas.
Figure 2: Measles cases in HSE-E, by CCA, weeks 32 – 41, 2011. (N=132)
During this outbreak period (weeks 32-41) all age groups were affected (Figure 3). However, the 5-9 year old had the greatest number of cases. Almost 70% of cases were unvaccinated or incompletely vaccinated. During this time there were 11 hospitalisations and the most frequent reported reason was for the treatment of seizures (three cases).
Figure 3: Measles case by age group, HSE-E, weeks 32 – 41, 2011. (N=132)
Control measures
An outbreak control team, chaired by the Director of Public Health (HSE-E) with representatives from public health, community medicine, the Health Protection Surveillance Centre (HPSC) and the National Immunisation Office (NIO), was established. Among the outbreak measures were the following:
- A schools’ based “Blitz of MMR” in north inner city Dublin and Ballymun took place, in early September, of all children attending primary school who had not received the recommended MMR vaccination.
- Prompt follow-up of all reported measles case by public health staff including liaising with general practitioners, managing clusters of measles, arranging swabs for diagnosis, staffing vaccination clinics and advising cases on appropriate follow-up.
- Informing all Dublin GPs by letter and email of the measles outbreak and requested to opportunistically vaccinate all children with MMR.
- Informing GPs in the outbreak area of additional outbreak measures including the vaccination of infants from 6 months and the expediting of MMR2 in specific circumstances.
- Providing information on the outbreak to acute hospital services, pharmacists and the Department of Education.
- Releasing multiple media messages to the public through the print media and local and national radio informing the public of the outbreak and of the need to have MMR vaccination to protect against measles.
Since early October there has been a gradual decline in the number of measles cases reported weekly in HSE-E to three cases reported in the week ending October 22nd. A combination of factors is likely to have facilitated the spread of measles in the affected area including: suboptimal MMR uptake, social deprivation, high population density and the absence of a school based immunisation service.
Vaccination with MMR is the only way to prevent measles infection. However, nationally and in HSE-E the MMR vaccination uptake at 24 months is currently 90% which is too low to prevent measles outbreaks occurring. MMR vaccine is safe and highly effective in preventing measles and its complications. Achieving a high immunisation rate with MMR vaccine is the only way to prevent measles.
Mary Ward, Orla Ennis and Margaret Fitzgerald on behalf of the outbreak control team.
