Measles outbreak in a Roma community in the Eastern region of Slovakia, May to October 2018

The study is designed as a case study analysing the epidemic outbreak of measles in the defined community.

The data from the patients diagnosed with measles during the outbreak was collected from the mandatory case notifications that were transmitted to the Epidemiological Information System of the Slovak Republic (EPIS SR). The patients were ambulatory or inpatients admitted to the Michalovce Hospital’s Department of Infectious Diseases and the Children’s Faculty Hospital in Košice between May to October 2018. The necessary data was obtained by interviewing the patients’ relatives, their paediatricians and the GPs as well as by reviewing the inpatients’ medical records.

Measles cases were classified according to the classification of measles cases as defined by the Commission Implementing Decision (EU) 2018/945 (5).

The suspected clinical cases were defined as having a fever with a body temperature ≥380C, maculopapular rash, and at least one of the following symptoms: conjunctivitis, coryza, cough, or Koplik’s spots (6).

The case-based reports provided data for disease onset, date of birth, sex, confirmation of diagnosis (i.e. laboratory confirmed, epidemiologically linked, or clinically compatible case), vaccination status, hospitalization and complications.

An outbreak of measles was defined as the occurrence of a chain of transmission of three or more cases linked in time and place and was declared by the Regional Public Health Authority (RPHA) in Michalovce and the National Public Health Authority of the Slovak Republic (NPHA of SR).

The data about vaccination status (MCV1, MCV2) was collected from the annual administrative monitoring in Slovakia. A retrospective review of vaccination coverage of measles was carried out for the years 1999 to 2018. The vaccination status of 24-month-old children was analysed according to date of birth from 1999 to 2016 (MCV1). The epidemiological data about measles transmission was obtained from the EPIS SR and the data about vaccination from the annual regular controls in Slovakia.

The ELISA tests were used to measure immunoglobulin M and G (IgM, IgG) antibodies. Tests were performed at the Alpha medical, s.r.o. (microbiological laboratory) and the National Reference Laboratory for Measles, Mumps and Rubella (NRL MMR) of the NPHA SR in Bratislava.

Measles were tested semi-quantitatively for IgM and IgG antibodies with Enzygnost Anti-Measles-Virus IgM/ IgG (Siemens) sets, and cut-off values for a positive IgM/ IgG>0.100 were calculated as the index of optical densities (OD) of the cut-off/OD of the sample, Rubella was tested with Enzygnost Anti-Rubella-Virus IgG (Siemens) semiquantitatively (OD cut off/OD sample), with cut-off values for a positive IgG>0.100. Mumps IgG was tested quantitatively with RIDASCREEN Mumps Virus IgG (R-Biopharm AG) with cut-off values for a positive IgG>244 U/ml.

Clinical specimens of four laboratory-confirmed cases were submitted to the WHO European Regional Reference Laboratory for Measles and Rubella at the Robert Koch Institute in Berlin, Germany to determine the genotype of the measles virus (MV) circulating during the outbreak as well as to identify its likely origin. The serum was sent for confirmatory testing and the throat swabs were submitted for virus detection, sequencing and genotyping of the MV RNA according to standard instructions.

Specific control measures for the target populations affected by the outbreak were implemented by the RPHA in Michalovce in accordance with the national guidelines, including conducting outbreak and contact investigation for cases, implementing isolation measures, catch-up and post-exposure vaccination and prophylaxis with immunoglobulin for people at high risk of developing severe disease, as well as providing information about the epidemiological situation. Proactive communication was carried out with parents, healthcare workers, microbiologists, hospitals, healthcare institutions, state administrations, the NPHA SR, the Ministry of Health of the Slovak Republic (MoH SR) and the Crisis Staff of the Michalovce District Office (7). Eligibility for prophylactic MMR vaccination and human normal immunoglobulin (HNIG) was assessed for all contacts and the healthcare workers. Those who had not been vaccinated appropriately for their age (i.e. the first dose of MMR vaccine at 15 months, the second dose at 10 years) were eligible for prophylactic MMR vaccination, in which case they were administered the vaccine within 72 hours of the contact with an infectious measles case. HNIG was considered for immunocompromised contacts, unvaccinated pregnant women, and selected infants under six months of age if they had been in contact with an infectious case in the previous six days (7, 8).

The letters with recommended control measures were sent out immediately: GPs were requested to check the immunization status of all contacts (children, adolescents and adults) and to immunize all those unvaccinated with one dose of MMR vaccine. The medical specialists in hospitals and outpatient settings were requested to be alert to the early detection, timely reporting, isolation, diagnosis, and treatment of measles cases. It was also recommended to hospitalize the patients with measles living in crowded households to ensure better conditions for treatment and care and to minimize the spread of the disease in communities with poor living conditions. The close Roma contacts with measles cases were isolated for 21 days at home.

The study uses descriptive data to characterize epidemic outbreak of measles, which is then used as a basis for the qualitative analysis of the implemented epidemic measures.

From May to October 2018 a measles outbreak was confirmed in Eastern Slovakia, specifically the region of Košice. First cases were imported from the UK (three imported and 1 imported-related cases). Measles spread to the Roma settlements in the Michalovce (416 cases from May 4 to September 20) and Sobrance (19 cases from May 25 to October 16) districts and affected the Roma population. During the outbreak period, four healthcare workers (HCWs) also developed measles in the Michalovce Hospital. A total of 439 measles cases were reported to the EPIS SR (Figure 1).

Figure 1

Figure 2 shows the measles incidence rate and level ofvaccination coverage from 1997 to 2018 in Slovakia. The long-term high-performing immunization programme at national and sub-national (regional) levels showed a significant drop from 99.6% to 95.2% and from 99.5% to 95.4%. The vaccination coverage (MCV1) in the monitored districts ranged from 99.7% to 97.3% and from 100.0% to 96.3%.

Figure 2

Figure 3 shows the number of the reported measles cases by date of symptoms onset. The outbreak reached its peak by July 2018 (week 28/2018), with 80 (18.2%) reported cases.

Figure 3

A total of 439 cases were reported with the dates of rash onset from May 4 to October 16, 2018 (weeks 19/2018 to 43/2018).

The median age for the total of 439 measles cases was 10 years (range: 0 month–51 years), while in 278 measles cases (63.3%) it was ≤14 years.

Measles was diagnosed after two or more days (from two to 12) following rash onset. 274 cases were laboratory confirmed and 165 were classified as probable cases. The reported complications included 39 cases of pneumonia. Out of total 439 cases, 288 patients were admitted to hospital with median hospitalization of 6.5 days (range: 1–10 days). The most common age group affected by measles were children <1 year of age and then adolescents in 15-19 years of age (157 cases; 35.8%). Out of 288 hospitalized cases, a ten-day stay in hospital was recorded in 67 patients, of whom 64 were children and adolescents aged 0-19 years.

Table 1 shows the characteristics of all cohorts (439 cases) and the characteristics of the 102 measles cases cohort with positive two doses vaccination status by gender, age and type of applied vaccine (monovalent, bivalent and trivalent vaccines). More than 90% of the cohort patients were vaccinated with two doses of trivalent MMR (measles, mumps, and rubella) vaccine.

Within the Roma cohort, 175 out of 435 cases were unvaccinated or had unknown vaccination status for measles. Four sick healthcare workers were vaccinated with two doses of bivalent measles-mumps vaccine. Out of 264 vaccinated cases, 137 (31.2%) received two doses and 127 (28.9%) only one dose of measles vaccine in their vaccination records. 155 measles cases (35.3%) were unvaccinated and 20 (4.6%) of unknown vaccination status. We additionally tested antibodies against rubella and mumps in a set of 137 patients with two doses of vaccine. Samples from 102 patients were examined.

A total of 274 measles cases were laboratory confirmed at Alpha Medical, s.r.o. (microbiological laboratory) from May 4 to October 16.

One hundred and two samples obtained from the measles cases with two-dose vaccination status were tested for IgG antibodies against measles, mumps and rubella at the NRL MMR of the NPHA SR.

For measles, 68 (66.7%) cases had positive IgM antibodies, 33.3% of them were equivocal and 23 (22.5%) had positive IgG. For rubella, only 20 (19.6%) cases had seropositive IgG levels, while for mumps higher positivity was detected in 60 persons (58.8%). The remaining cases had negative test results.

Table 2 contains the proportion of persons with positive and negative serology results for a rubella IgG antibody test. Across all age groups of the measles cases, we can detect only a small percentage with a positive serology result of rubella IgG antibody test, ranging from 10.0% in the age groups of 10–14 and 45–54, and up to 30.0% in the 35-44 group.

Clinical specimens of four laboratory confirmed cases were tested in RKI Berlin. Sequential analysis of two samples showed measles genotype B3, dist. sequence in MeaNS: 5258, identical to Nmed Strain MVs/Bradford. GBR/13.18.

Staff of the RPHA in Michalovce visited the Roma settlements several times, together with Roma health mediators (RHM), to identify contacts and search for additional cases and close contacts. Close contacts (and especially those 18 years or younger) were invited to GPs for post-exposure prophylaxis. The RPHA informed the local hospital, emergency departments, paediatricians, GPs and the local media, and urged physicians to investigate all suspected measles cases, to isolate them if infectious and to notify cases immediately. Simultaneously, they highlighted a need for verification of the measles immunity status of all unvaccinated hospital staff, and for vaccination of all those susceptible to infection.

Following the risk assessment of the situation related to the reported rising numbers of measles cases in many European countries (mainly in the Czech Republic, May 2017) and the permanent threat of importation of measles cases, the NPHA SR sent out an official warning letter to all RPHAs on May 2017.

During the measles outbreak in 2018, letters with recommended control measures were prepared by the RPHA in Michalovce (repeatedly from May 7 2018), the NPHA SR (May 28 2018), the Crisis Staff of the Michalovce District Office (July 13 2018).