BOGOTA, Feb 19 (Thomson Reuters Foundation) - The mosquito-borne Zika virus spreading through the Americas, linked to severe birth defects in Brazil, will not be controlled over the long-term unless governments improve poor living conditions in the region’s sprawling slums, experts say.
Across Latin America, poor neighbourhoods crammed with shacks built with bricks, scrap metal and wood, often surrounded by rubbish and without access to running water, are a common feature of the urban landscape.
Such an environment has fuelled the spread of the Zika epidemic and other diseases carried by the Aedes aegypti mosquito, such as dengue and chinkungunya, and poor communities living in slums often bear the brunt, experts say.
“People living in crowded circumstances, a lack of piped water, and poor sanitation have given rise to the perfect set of conditions for the transmission of mosquito-borne viruses like Zika,” said Amy Y. Vittor, assistant professor in medicine at the University of Florida’s Emerging Pathogens Institute.
“The lack of decent living conditions, which gives rise to not only epidemics such as Zika and dengue but also childhood diarrheal diseases, must be addressed,” she told the Thomson Reuters Foundation in a phone interview.
Around 113 million people across Latin America - or nearly one in five people - live in slums, partly a result of mass migration from rural to urban areas from the 1950s onwards as people moved to the city in search of jobs.
Such rapid urbanisation has often happened without proper urban planning, allowing slums to expand without basic infrastructure and services.
Many slum dwellers store water in buckets and collect rain water in root-top tanks, and water also collects in discarded tyres, making ideal breeding grounds for mosquitoes.
“You have a lot of places where water can be stored and where mosquitoes can lay their eggs, making people living in slums vulnerable,” said Ana Carla Pecego, an infectious disease specialist in Rio de Janeiro.
The Zika virus has spread to more than 30 countries and territories, with Brazil the worst hit by the outbreak, followed by Colombia.
Much remains unknown about Zika, including whether the virus actually causes microcephaly, a condition marked by abnormally small head size that can result in developmental problems. Brazil is investigating the potential link between Zika infections and more than 4,000 suspected cases of microcephaly.
The World Health Organization (WHO) said on Friday there was an increasing accumulation of evidence of an association between the Zika virus and microcephaly, a neurological disorder in babies, but it could take 4-6 months to prove.
The WHO declared the outbreak an international health emergency on Feb. 1, citing a “strongly suspected” relationship between the Zika virus and infection in pregnancy and microcephaly.
The WHO says the Aedes aegypti mosquito has shown “a remarkable ability to adapt to changing environments,” including rapid unplanned urbanisation.
Current efforts are focused on protecting people, especially pregnant women, from bites and eradicating the mosquito breeding sites in affected areas.
For the poor living in densely populated slum areas it is harder to avoid getting bitten, some experts say.
“When you have a lot of people living together in one small place it makes is easier for the Zika virus to spread and for mosquitoes to bite many people in a small space,” Pecego said.
People living in affluent neighbourhoods have access to running water and can protect themselves better by using insect repellent, pesticide-treated mosquito nets, screens on windows and air conditioning - options not often available to slum dwellers.
During heavy rainfall, slums often flood because of non-existent and or blocked drains, leaving puddles of stagnant water outside people’s homes where mosquitoes can breed.
In Colombia, an El Nino-related drought has meant more people have resorted to storing water. In Cali, Colombia’s third city, rationing of tap water due to drought has prompted residents to store more in containers.
In neighouring Brazil, tens of thousands of health workers are going door-to-door to eradicate mosquito breeding sites in homes, along with a massive insecticide-spraying operation to stem the Zika outbreak.
Pecego said previous dengue outbreaks have shown that such methods can control the number of cases only for “a brief period to time” and that the disease flares up again.
"To control the Zika virus over the long-term we have to invest in sanitation and health education, not throw garbage in the streets and rivers and cut out the necessity for people to store water," she said. (Reporting by Anastasia Moloney, editing by Ros Russell.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit news.trust.org)