Tonga

Tonga Measles Outbreak 2019-20 - Situation Report #12

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1. Summary of Situation Background

The outbreak of measles in Tonga began in early October 2019, following the return of a national youth team of Tongan rugby players from New Zealand. The index case developed measles while in New Zealand. Subsequently, a further 12 teammates developed laboratory-confirmed measles after returning to Tonga. The early outbreak involved mainly teenagers from associated schools on Tongatapu and Vava’u Islands. Presently, all 70 villages on Tongatapu Island have reported cases. A small number of cases have been identified on the Islands of ‘Eua, Ha’apai and Niuatoputapu. Since the initial two waves of the outbreak, cases are now being seen widely in all age groups.

An inter-disciplinary Ministry of Health Epidemic Task Force usually meets weekly to advise on management of the outbreak. In addition to routine outbreak response activities, a time-limited vaccination program targeting secondary school students and 6-11 months infants was initiated and completed. Mass Vaccination campaign targeting the 10-24-year-old age group not picked up in the school vaccination program was completed throughout Tonga on Friday 20 December 2019.

Note: Refer to earlier SITREPS for further detail of the initial cases and response.

2. Current Situation

There is ongoing transmission on the Islands of Tongatapu and Vava’u; the last case onsets on Ha’apai, ‘Eua, and Niuatoputapu islands were 14/12/2019, 08/12/2019, 14/11/2019, respectively.
Since the last situation report, 16 new measles cases with onset dates in the last week were reported in Tonga, including 13 cases from the main Island of Tongatapu and 3 cases from Vava’u Island. They were 10 males and 6 females between the ages of 6 months and 23 years old.

As of 31 December 2019, 612 confirmed or suspected cases of measles have been identified in Tonga. The majority 534 (87.2%) cases have occurred on Tongatapu and 66 (10.7%) have occurred on Vava’u Island. Case presentations have been reported to be mild with 18 hospitalisations and no death. The majority of the cases have been managed by home isolation and all patients have been discharged. Given the duration of illness is typically less than 2 weeks, it is estimated that at least 96% of the 612 reported Measles cases will have already recovered from their illnesses.

Figure 1 (below) shows the epidemic curve for the current outbreak in Tonga. Most of cases (blue) were reported from the Island of Tongatapu.

Figure 2 demonstrates the breakdown of cases by sex. Consistent with early transmission through male boarding schools, most cases have been among males, with the proportion of cases among females increasing as the outbreak progressed. A total of 96 cases have occurred in children aged less than 5 years, while cases among adolescents and young people continue to form the majority of the cases in this outbreak, with 482 (79%) cases occurring in people aged 10 to 24 years (Table 1 and Figure 3).

Key events/ issues since last SITREP

  • Supplemental immunisation activities for measles have been underway since 10 October 2019, in conjunction with continued routine childhood vaccination. These efforts continue to target groups at greatest risk of measles infection, as well as those at greatest risk of severe illness, including:

o Extended family contacts of suspected and confirmed cases o Adolescents and young adults aged 10 to 24 years

o Outbound travellers aged 6 months to 24 years without documented evidence of 2 doses of measles-containing vaccine

o Migrant workers

o Infants 6-11 months-old for a ‘zero’ dose

o Select other groups

  • A targeted mass vaccination campaign of 10 - 24-year-olds not otherwise vaccinated during the nationwide school campaign was conducted on 26 November 2019 and 17 December 2019 through 20 December 2019.
    A total of 8,400 persons were vaccinated during the campaign on the Islands of Tongatapu, ‘Eua, Ha’apai, and Vava’u; those on Niua were vaccinated earlier.

  • A grand total of at least 27,691 persons have been vaccinated through 31 December 2019 (figure 4).

  • Government was officially closed for the year on Friday 20 December 2019. However public health and clinical services are ongoing with provision for surge capacity as needed

  • A two-person WHO and GOARN team is working with Tonga MOH to support the measles outbreak Ongoing and planned activities:

  • Weekly ETF meetings to conduct risk assessment to guide response

  • Vaccination efforts targeting priority groups

  • Contact tracing and post-exposure vaccination of extended family contacts of cases as part of intensive case follow up

  • Enhanced surveillance activities, including completion of minimal case report form (CRF) by outpatient clinic staff and improved mapping of contacts

  • Complete verification of measles immunisation records for cases, with a focus on immunisation records for cases aged less than 10 years and provide a summary of MCV immunization coverage status

  • The NEMC has been activated including a meeting of the Health and WASH cluster for cyclone preparedness.
    The MOH will be monitoring need for vaccination in evacuation centres

  • Work with representatives of churches, village and town officers and other organisations to continue to postpone mass gatherings wherever possible

  • Ensure collection of additional samples as the outbreak wanes and timely turnaround time of results