1. Summary of Situation
An outbreak of measles in Tonga occurred following the return of a squad of Tongan rugby players from New Zealand where one player had developed the illness. A further 12 players developed measles on their return to Tonga. Samples from 6 of these cases were laboratory confirmed as measles. The outbreak has involved mainly teenagers from schools on Tongatapu as well as students from Vava͛u High SĐhool. Cases are epidemiologically linked to the initial imported cases. The Ministry of Health Epidemic Task Force has been convened comprising public health, clinician and laboratory representatives to advice on the management of the outbreak.
Note: Refer to earlier SITREPS for further detail of the initial cases and response.
2. Current Situation
As at 5th November, 177 cases of confirmed or suspected measles have been identified in Tonga. Clinicians have reported that most cases are experiencing a mild illness.
The attached charts outline the results of analysis of current case information. The epidemic curve reflects a propagated outbreak matching the incubation period for measles (Figure 1). Figure 1 demonstrates the cases in Vava͛u high sĐhool studeŶts (in red) stemming from measles in two of the returned rugby players. Figure 2 demonstrates that while males predominate, consistent with the transmission of disease through the boys schools, females have contracted measles as the outbreak has gone on. Four cases have been reported in infants less than 12 month of age, one case in a two-year old child and two cases in children 5-9 years of age (Figure 3). Predominate symptoms include rash (98% of cases) and fever (82% of cases) (Figure 4). Cases in females have occurred mainly in the 15-19 age group followed by the 10-14 age group as for the males (Figure 5). Identifying vaccination history for cases has proved challenging. Of 177 cases, vaccination history has been found for 63 cases. Of these 63 cases, 43 (73%) have a two-dose history with MR vaccine and the remainder have a one dose history. The remaining cases are awaiting verification of vaccination histories.
There is currently no evidence to suggest that new lines of transmission have occurred.
Key events/ issues since last SITREP
FourteeŶ Đases have ďeeŶ reported froŵ Vava͛u, all in the 15-19 year age group and linked through the school. This is a co-educational high school and it is of note that 5 of the cases are in girls.
Measles occurred in a touring Tongan Futsal team which travelled to New Zealand on 14th October where one of the team became unwell on 19th October and was subsequently diagnosed with measles. The team was staying in shared accommodation. While this case remained in NZ, the remainder of the squad went onto New Caledonia prior to their infectious period. Public health in New Caledonia administered post exposure vaccination to 4 members of the squad who did not report a history of two doses of MCV. The other members described a two dose MCV vaccination history and were not vaccinated. By 1st November, 6 of the boys became unwell with measles including 4 boys with a reported two-dose vaccination history and 2 of the boys given PEP in New Caledonia. The unwell boys have remained in New Caledonia until the infectious period has passed while the remainder of the squad returned on 4th and 5th November. Public health action has been taken to quarantine and provide education. Full details of the squad and vaccination histories are being collated. Serology results for 5 of the cases show IgG+/IgM- while the other is IgG+/IgM equivocal. PCR results to follow.
Given preliminary evidence of non-protective immunity in the teenage cohort, contacts of cases which have a two-dose history of vaccination with MCV may be considered at risk of measles and should be managed accordingly.
Advice has been received from MFAT that goods requested to support the measles outbreak had been despatched and should arrive in Tonga 6-7th November.
A supply of N95 masks and hand gel was received from WPRO.
A supply of Capon swabs for sampling due to arrive from WHO DPS on 7th-8th November.
Samples from 18 people suspected of having measles were sent to VIDRL on 29/10.
2500 doses of MR vaccine ordered through UNICEF arrived 29/10