3Q: Elfatih Eltahir on what malaria and Dengue can tell us about Zika
Environmental management approaches may be key in combating mosquito-borne infectious diseases.
Like many engineers at MIT, Elfatih A. B. Eltahir builds models. But his models, numerically heavy and integrating satellite, atmospheric, and field intelligence, do not pop out of a 3-D printer.
He and his team simulate regional climate processes to understand land surface hydrology. It turns out that by understanding where water meets land can not only shed light on natural systems, but also reveal how infectious diseases spread and inform environmental management solutions.
A professor and associate department head in civil and environmental engineering, Eltahir has long set his sites on a particularly “nasty guy” — the Aedes aegypti mosquito — responsible for one of the most devastating of viruses, Dengue, and now the newsworthy Zika. The MIT School of Engineering asked him to explain how his research helps put the Zika virus outbreak into context and suggests some potential approaches to get ahead of its imminent approach to this country and elsewhere in the world.
Q: While you do not study Zika specifically, you have conducted extensive work on some of its “close cousins” such as malaria and Dengue. How does your research provide some context and clarity about what’s been happening with the rise of Zika?
A: My team is interested in the connections of infectious disease to the environment and climate. We have done work on malaria and studied its transmission by the Anophelesmosquito. We can move this expertise to look into similar viral diseases, like Dengue, and that, in turn brings us closer to Zika, as all three are like cousins in the same family.
The way Zika gets transmitted is similar to Dengue, as the same nasty guy, Aedes aegypti, is responsible. We have conducted extensive work in Singapore to understand the transmission of Dengue and that revealed how mosquitoes are able to breed outdoors, not just indoors as once assumed by many. Further, the Aedes aegypti eggs can resist desiccation. A female can throw some eggs in a body of water and even if that water dries up, once water is added, the eggs can then hatch. This means we are dealing with something that is much harder to control.
We also have some understanding of how Aedes aegypti relates to the environment. When the climate gets warmer the areas where these mosquitoes can exist are likely to expand and that may be potentially why we are seeing the increase in Zika now, but we haven’t studied those aspects yet. Dengue, for example, has a particular season; we have been trying to understand the determinants of that seasonal cycle in Singapore.
Q: Some might find it surprising that MIT engineers, not just biologists, are working to understand and combat the spread of infectious diseases. As an engineer, do you take a different approach to this problem?
A: In essence, you are asking, how do we get into the picture? We do not study the development of new vaccines (like our friends in the Broad Institute are doing) or try to understand the pathogenesis of a virus. In civil and environmental engineering we know how to model and monitor the environment, and we bring that modeling and monitoring capacity to bear on phenomena like infectious diseases. In our approach to disease control we emphasize environmental management: how to manage the environment to make life difficult for the mosquitos that carry the disease.
People now are running toward “let’s have a vaccine for Zika.” With a vaccine they are looking for a quick fix, a clean solution. The success stories fighting vector-borne diseases in the past tell us that while environmental management is tedious and dirty, it works. Think about it. If such an approach had been taken with the Aedes aegypti mosquitoes that carry Dengue we would have potentially not have seen Zika take hold!
Environmental management means eliminating the breeding sites and habitats of the mosquitoes. In the case of a parasite like malaria, that also means the screening of individual homes. In fact, malaria was practically eliminated in Italy and even here in Boston and some other parts of the world, mainly through environmental management. All of the success we have seen in the past with combating mosquito-borne infectious disease has been through environmental management.
By contrast, Dengue is the fastest growing infectious disease in the world, exacerbated by urbanization, increases in population, temperature warming, and the travel and migration of people. Despite decades of work, we still do not have a cure or a vaccine.
Q: When a vaccine is not available for Zika and similar viruses, what steps should be taken and what might this mean for all of us who live here?
A: The ultimate solutions for malaria, Dengue, and now Zika that I see are all local ones. They have to be. Regional public health authorities and governments will have to step up and coordinate if they want to get ahead of Zika. Moreover, these kinds of disease control activities have to be sustained. Why?
When you go after malaria in Africa, for example, and are able to reduce it significantly, you also reduce the population’s immunity. So if it comes back again, it hits hard. So it is important to sustain any infectious disease control activities over the long term.
I’ve had recent conversations with public health scientists in the state of Massachusetts about developing a collaborative, integrated research effort to study the potential spread of similar mosquito transmitted viruses (Dengue, Chikungunya, and Zika) in the area. Now is the time to go after new species of mosquitos and eliminate any new colonies of Aedes aegypti. If we wait for them to establish, it will be too late.