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Rural-to-Urban Transition May Explain Viral Outbreaks: Vietnam Study

A dirt path winds through the forest in Phu Quoc, Vietnam. The nation is rapidly urbanizing, which brings risk of contact between humans and infected animals.

Vietnam has a possible lesson for the world as the global community copes with the COVID-19 emergency — monitor the places where odds of an outbreak are highest. Research indicates these are not the most urban or the most rural areas, but rather those that are in transition.

Scholars from the East-West Center in Hawaii based this assessment on a review of Vietnam’s response to an avian flu outbreak in 2003. In researching that outbreak, the scholars found that infection rates were highest in areas that were in the process of urbanization, and thus had a mix of conditions, such as different rates of toilet access and diverse bird populations near national highways.

Thus, governments may have higher odds of detecting a viral outbreak early and efficiently if they monitor such urbanizing areas, say James Spencer, Sumeet Saksena and Jefferson Fox, all senior Fellows at the Center, which is a nonprofit organization for research and education.

“On a practical level, information on the link between urban development and disease outbreaks can help government agencies identify which locations are most likely to experience an outbreak of avian influenza so that prevention efforts can be less costly, more targeted, and more effective,” the Fellows wrote in a joint analysis April 1 for the Center.

They added, “The concepts and methodology that were developed for this study could easily be adapted to many other disease threats, ranging from SARS, Ebola, and dengue fever to the current pandemic of COVID-19.”

The authors were referring to a study, first done in 2017, which identified regions of Vietnam that were at risk of infection because as they urbanized, they had uneven levels of sanitation and a high chance of interaction between humans and animals.

Those factors are relevant for the coronavirus in 2020 because some scientists believe that today’s disease originated in a transmission from animals to humans in China, which borders Vietnam and shares its experience of an uneven transition to urbanization.

Bill Gates’ warning

Philanthropist Bill Gates also discussed viruses and the rural-urban contrast in a TED talk that went viral for its seeming prescience. In 2015, he examined an Ebola emergency that killed 10,000 people, mostly in rural areas in West Africa.

“It didn’t get into many urban areas, and that was just luck,” he said. “If it had gotten into a lot more urban areas the case numbers would have been much larger. So next time we might not be so lucky.”

Expanding on the point made by Gates about Ebola, the East-West Center Fellows explained how Vietnam’s move from rural to urban development affected its avian flu cases, and what that could mean as the world fights the coronavirus.

A hen tends to her chicks outside Ho Chi Minh City, Vietnam.
A hen tends to her chicks outside Ho Chi Minh City, Vietnam.

The 2017 study, conducted with Vietnamese colleagues Nong Huu Duong and Chinh Tran, noted that as cities grow in developing countries, the demand for eggs and chicken increases.

“Much of this demand is being met by large farms in the peri-urban areas surrounding cities,” the study said. “In Vietnam and other countries of Southeast Asia, numerous intensive chicken farms have sprung up in these areas.”

These “peri-urban” areas transitioning from rural to city life have a variety of birds, a location near highways to help with transporting goods, and sanitation inequality among those who have toilets that flush and those who don’t.

“This uneven process can be characterized as a period of confusion and social and environmental instability,” the study said. “One important result is a heightened risk of infectious disease in both humans and domestic animals.”

Farmers raise chickens outside cities to serve urban customers; if those farmers contract avian flu, the disease could be transported into the nearby city, where the denser population would help it spread even faster. That could have been the case with COVID-19 as well.

The scholars recommend that governmental authorities target their monitoring in these peri-urban areas, so they can see early signs of an outbreak and respond, such as by culling chickens. And then if authorities agree that “discrepancies in sanitation” cause outbreaks, they “might reduce disease risk by increasing efforts to standardize community infrastructure,” Spencer and his colleagues said.

“For example, they might prioritize the introduction of flush toilets more widely in communities where access to modern sanitation is currently mixed,” they said.

Millions of chickens were slaughtered in Vietnam and elsewhere to stop the avian flu from spreading.