Living Smart

010 011 I ENGINEERING & TECHNOLOGY Small blueprint for erasing dengue bite Prof. Angela WU Assistant Professor, Division of Life Science, and Department of Chemical and Biological Engineering M ore than 20 cases of dengue fever were diagnosed in Hong Kong in the recent outbreak. Although there were no deaths, dengue fever can sometimes become severe dengue or dengue hemorrhagic fever, which has no known cure and could be fatal. Luckily, dengue fever is not very common in Hong Kong (there are typically fewer than 100 cases per year), especially compared to our Southeast Asian neighbors like Singapore (between 5,000 and 23,000 cases per year). Many Hongkongers are concerned about staying safe from dengue fever. Among the potential strategies for prevention, one cutting- edge solution is the use of “gene-drive” mosquitoes. A gene is a small section of the DNA blueprint that makes us who we are. Normally, a gene from one parent is inherited in only half of the children, and in nature, if a gene is harmful it will quickly be erased from the population. Gene drive, however, is a cleverly engineered gene that is inserted artificially into an organism’ s DNA, which is then passed down from one parent to all of its children, even if that gene is harmful to the population. One dengue-fighting mosquito gene drive works by making a toxin in the mosquitoes that kills them while they are young. By releasing these mutant mosquitoes into the wild and letting them breed, the toxin-producing gene drive will eventually kill the whole population of mosquitoes leaving no carriers to transmit the disease. Gene drive is a powerful tool indeed, but will it work? Could genetically engineered insects harm the environment or cause other problems? In Brazil, over one million people get dengue fever every year. To fight the disease, gene-drive mosquitoes were released in a few test cities in 2016. No severe ecological effects have been observed so far. The mosquito population in the cities was reduced by over 60 percent, and the number of dengue cases was also reduced by about 50 percent. However, could mosquitoes develop resistance to the engineered gene, meaning that it would no longer kill them? Could the engineered gene accidentally spread and kill other species that cause no harm to people? Could the dengue virus be spread by other species in the future? One final consideration for Hong Kong is cost. Brazil paid over HK$8 million for two years of mosquito deployment in just one city. There are less costly and less risky options to prevent dengue fever, like surveillance and insect repellent, which are highly effective if deployed correctly. Given that the number of dengue cases in our city is relatively low and the potentially unknown risks of gene drive, the most high-tech option may not be the most cost- effective and most sensible solution for us. Published on November 21, 2018