Why dengue fever prevention calls for attention to the big picture, not just the pests in our own backyards

Robert Peckham and Ria Sinha say Hong Kong can draw on both its history of epidemics and the talent and technological expertise in the Pearl River Delta region to tackle mosquito-borne diseases

PUBLISHED : Tuesday, 11 September, 2018, 12:03pm
UPDATED : Wednesday, 12 September, 2018, 3:14pm

With 28 local cases of dengue fever confirmed in August, Hong Kong’s fevered history is rebounding in the present.

According to the World Health Organisation, 40 per cent of the global population is at risk of dengue, with Asia at the epicentre. Last month’s outbreak in Hong Kong was the worst in recent times.

Despite the city’s much-vaunted epidemic surveillance system and a widely publicised anti-mosquito offensive, there is a public perception that health authorities have been caught off guard. For many, it appears to be a case of too little too late.

Could Hong Kong have been better prepared? The short answer is yes. There is always more to be done. Over the past two decades, data from the Centre for Health Protection has shown a marked increase in imported cases of dengue and other mosquito-borne diseases, with a rise in locally acquired infections over the past five years.

An outbreak of over 40,000 cases of dengue in Guangdong in 2014 shows the potential for a major epidemic in Hong Kong. The territory is no stranger to mosquito-borne diseases. They wracked the early colony, which had a reputation as a “fatal island”. Malaria was endemic and dengue outbreaks occurred periodically, with the first recorded epidemic in 1872. Japanese encephalitis, chikungunya and Zika are contemporary threats.

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Hong Kong’s changing environment has shaped its disease ecology. While development pushed the anopheline mosquitoes responsible for malaria transmission back to rural areas and local transmission was halted in 1998, the city has provided a favourable habitat for other disease-carrying mosquito species. One of the most successful urban dwellers is Aedes albopictus, a vector of dengue, chikungunya, West Nile virus and Zika virus among others.

Finding the balance between official and community responses will be key to an effective long-term disease management and prevention strategy

The recent dengue outbreak is a reminder that mosquito elimination alone is inadequate to meet the challenge. Responsibility for mosquito control has long been contentious.

Public health education primes Hongkongers to avoid mosquito bites and destroy potential breeding sites. Meanwhile, residents are asked to report localised mosquito problems to the Food and Environmental Hygiene Department, reinforcing the idea that disease control is ultimately the remit of the government. Finding the balance between official and community responses will be key to an effective long-term disease management and prevention strategy.

Then there is the relegation of mosquito-borne diseases to the second tier, particularly following outbreaks of bird flu in 1997 and severe acute respiratory syndrome (Sars) in 2003. Both outbreaks originated in Southern China and Hong Kong government health protection refocused on the urgent challenge of safeguarding borders and entry points. As a health threat, mosquitoes are viewed, at least by the public, as dead history.

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But Hong Kong’s proximity to countries with endemic diseases makes it exceptionally vulnerable. In Southeast Asia and beyond, under-resourced health systems are struggling and accurate data is lacking or obfuscated by politics. Drug and insecticide resistance are jeopardising global health goals.

Hong Kong is uniquely placed to develop a novel approach that marries cutting-edge know-how with historical experience

Most dengue cases in Hong Kong originate from Asian countries. Local insecticide spraying may have high media visibility, but it is a limited and short-term solution viewed in the larger context of growing worker mobility, mass tourism and environmental transformation across the region.

Enhanced vigilance and preparedness will be essential, not only to avoid a repeat of this year’s dengue outbreak but to tackle the longer-term threat of the disease becoming entrenched. It will be a wise investment, as the path cut by dengue could become a route for other regionally endemic or emerging vector-borne diseases, including Zika.

Moreover, Hong Kong is uniquely placed to develop a novel approach that marries cutting-edge know-how with historical experience. Improved cross-border health communication and new technologies, including digital sensing systems and next generation diagnostic tools, offer potential for pre-empting and managing disease threats.

What Hong Kong can learn from Taiwan in the battle against dengue

Today, the Pearl River Delta is recognised as a global technology hub. This innovation, and the talent that sustains it, should be harnessed for a radical public health agenda. Meanwhile, to grapple with the historical consequences of ecological change for disease emergence, we need to embrace the big view. Now more than ever, it’s time to remember the future.

Robert Peckham is professor of history and director of the Centre for the Humanities and Medicine at the University of Hong Kong. Ria Sinha is a senior research fellow at the Centre for Humanities and Medicine