1. Summary of Situation
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. The early outbreak involved mainly teenagers from associated schools on Tongatapu and Vava’u Islands. Since the initial two waves of the outbreak, cases were widely reported in all age groups but are now waning.
An inter-disciplinary Ministry of Health Epidemic Task Force (ETF) 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 has been completed.
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 [Table 1].
Since the last situation report, 6 new measles case-patients were reported in Tongatapu and 3 cases were added retrospectively to the cumulative number of cases. They were 7 males and 2 females between the ages of 6 months and 19 years old.
As of 16 Jan 2020, 639 confirmed or suspected cases of measles have been identified in Tonga including 52 labconfirmed cases. The majority, 561 (87.8%) cases have occurred on Tongatapu, and 66 (10.3 %) have occurred on Vava’u Island. Case presentations have been reported to be mild with 20 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 99% of the 639 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 gender. 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 105 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 - 500 (78%) cases occurring in people aged 10 to 24 years (Table 2 and Figure 3).