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 and February 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 5 th February 2020, 656 confirmed and suspected cases of measles have been reported in Tonga. Till date, 98 specimens have been tested for measles, of which 78 (79.6%) have been PCR laboratory confirmed.
Of 656 cases, 578 (88.1%) cases occurred on Tongatapu and 66 (10.1 %) occurred on Vava’u Island. Figure 1 shows the epidemic curve for the current outbreak in Tonga.
Ongoing transmission of measles virus in Tongatapu and Vava’u. Onset of illness for most recent case in Tongatapu was 1 st February 2020. Onset of illness for last reported case in Vava’u was 8 Jan 2020 (28 days todate). Islands of Ha’apai, Eua and Niuas have interrupted transmission (Table 1).
Throughout the course of the outbreak, most cases presented with mild symptoms, and were mostly managed by home isolation.
Between October 2019 and 25th December 2019, there were 20 measles related hospitalisations. All cases recovered completely and were discharged. No deaths have been reported till date.
Between 30th January and 5th February 2020, four additional cases were reported. Of these, clinical confirmation for two cases is pending. All reported cases were from the island of Tongatapu. The two suspect cases were females aged 15 and 24 years.
Of the 656 cases, majority (452, 31.1%) of cases have been in males. This is consistent with early transmission occurring in male boarding schools.
Figure 2 presents age and gender graph for all cases of measles in the current outbreak. Majority (435, 66.7%) cases occurred in persons aged 10 to 19 years (Figure 2 and Table 2).
Vaccination records have been verified for 560/652 (85.9%) cases. In-depth results will be available following complete verification.