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 declining.
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 was conducted between October and December 2019. Additional immunization activities have been conducted in January to target the 1-9 year olds.
Note: Refer to earlier SITREPS for further detail of the initial cases and response.
2. Current Situation
As of 29 Jan 2020, 652 confirmed or suspected cases of measles have been reported in Tonga including 72 labconfirmed cases. Of these, 574 (88.0%) cases occurred on Tongatapu and 66 (10.1 %) occurred on Vava’u Island. Cases have mostly presented with mild symptoms. Till date there have been twenty (20) hospitalisations (none since 25-December-2019), and all cases have been discharged. No deaths have been reported till date. Majority cases have been managed by home isolation.
There is ongoing transmission of measles virus in Tongatapu and Vava’u. Onset of illness for most recent case in Tongatapu was 20 Jan 2020. Onset of illness for last reported case in Vava’u was 8 Jan 2020 (14 days todate). Islands of Ha’apai, Eua and Niuas have interrupted transmission (Table 1).
Between 23rd and 29th January 2020, five additional cases were reported, including two cases which were included retrospectively. All cases are from the island of Tongatapu. The three new cases were in one female (12yo), and two siblings living in the same household (a 21yo male and 16yo female). Vaccination status is pending verification.
Figure 1 shows the epidemic curve for the current outbreak in Tonga. Majority of cases are from the island of Tongatapu (in blue).
Figure 2 presents the epidemic curve by gender. Of the 656 cases till date, majority (452, 69.3%) of cases have been in males. This is consistent with early transmission occurring in male boarding schools.
Figure 3 presents age and gender graph for all cases of measles in the current outbreak. Majority (435, 66.7%) cases have occurred in persons aged 10 to 19 years (Figure 3 and Table 2).
Vaccination records have been verified for 560/652 (85.9%) cases.