Dengue messaging reached more people every year — but knowledge and weekly larva control did not follow

Thailand has run dengue campaigns through mass media for decades. Across three years (2013–2015) that bracket the large 2013 outbreak, this study asks how often Thai people saw dengue information in the media, how accurately they understood the mosquito, and whether they destroyed breeding sites weekly as recommended — and whether those three things moved together.

Three survey rounds in 2013, 2014 and 2015 across 25 provinces (24 chosen by high and low incidence, plus Bangkok). 7,772 respondents in total (2,323 / 2,842 / 2,607), aged 15 and over and literate, recruited by accidental sampling — each round was a different set of people, not the same people followed over time. Media exposure was measured as the frequency of seeing dengue information on five levels from every day to never; knowledge with three true/false statements; behaviour as how often respondents eliminated breeding sites. Year-to-year means were compared with repeated-measures ANOVA and t-tests.

• Media exposure rose every year. The mean frequency score went from 2.84 (2013) to 3.31 (2014) to 3.37 (2015), a significant difference (p = 0.001). In 2013 the largest group saw dengue information only once a month (32.4%); in 2014 the largest group saw it more than three times a week (35.2%).
• Knowledge did not climb with it. The average share of correct answers went 73.6% → 81.5% → 73.3% — up for one year, then back down. The authors read 2014 as the alert that followed the 2013 outbreak, fading once the recovery period set in.
• The most stubborn misconception concerns water. Only about a third (33.5% in 2013, 30.0% in 2015) knew that the dengue mosquito does *not* lay eggs in dirty, smelly water; the authors suspect people conflate malaria control with dengue control. Other statements were answered correctly by more than 90%.
• Action went backwards. The share eliminating breeding sites weekly, as recommended, fell from 61.2% (2014) to 48.3% (2015), while the share doing so less than once a week rose from 28.0% to 35.2%.
• The authors' conclusion is blunt: a media campaign aimed only at raising awareness, without community participation, proved ineffective at controlling dengue. Concern about dengue in Thailand is episodic — it rises with imminent danger and subsides afterwards.

For health communicators the lesson is that reach is not a success measure: the media reached more people each year while behaviour slipped. The “dirty water” misconception survived two years of rising exposure, which suggests the messages being sent did not confront that specific error — a campaign should first find out what people actually get wrong, then aim there. The authors recommend a year-round campaign rather than outbreak-driven bursts, a move towards the social media people actually use, and tying media work to community programmes that get people to act.