An epidemic of dengue 3 in far north Queensland, 1997-1999
Hanna, J.N.; Ritchie, S.A.; Phillips, D.A.; Serafin, I.L.; Hills, S.L.; van den Hurk, A.F.; Pyke, A.T.; McBride, W.J.; Amadio, M.G.; Spark, R.L.
Medical Journal of Australia 174(4): 178-182
2001
ISSN/ISBN: 0025-729X PMID: 11270758 Document Number: 526545
Epidemiological and laboratory investigation of cases, entomological surveys and phylogenetic analysis of dengue virus isolates were conducted to describe an epidemic of dengue type 3 that occurred in far north Queensland during 1997-99 and its influence on the further development of dengue prevention and control strategies. Main outcome measures were numbers and characteristics of confirmed cases; Breteau Index (BI; number of containers breeding Aedes aegypti per 100 premises); effect of control measures on mosquito populations; genetic homology of epidemic virus with other dengue virus isolates. The epidemic lasted 70 weeks and comprised 498 confirmed cases in 3 towns (Cairns, Port Douglas and Mossman); 101 patients (20%) were admitted to hospital. Median interval between symptom onset and notification was 7 days (range, 0-53 days), and cumulative duration of viraemia of public health significance was 2072 days. BIs in affected areas were high, particularly in Mossman (45) and Port Douglas (31). Control measures significantly reduced mosquito populations assessed as number of ovitraps containing A. aegypti eggs and mean number of eggs per trap (P<0.05 for both). However, transmission persisted in several foci, in part due to undetected waterfilled containers breeding A. aegypti. The epidemic virus belonged to serotype 3; phylogenetic analysis suggested it was imported from Thailand. The epidemic had greater morbidity than other recent Queensland epidemics of dengue and was harder to control, necessitating substantial revision of the Dengue Fever Management Plan for North Queensland. The epidemic's severity supports the hypothesis that dengue viruses from South East Asia are more virulent than others.