Diseases may emerge and cause worldwide pandemics

Publicação: 10 de January de 2013

Doenças podem emergir e causar pandemias em nível mundial

Clustering within households and a lack of basic hygiene are a reality in large tropical cities


“The next pandemic to confront us will probably come from wildlife”. This statement was made by the American scientific writer David Quammen, in the book Spillover: animal infections and the next human pandemic. In an interview with the magazine Epoca, Quammen discusses his book, which is the result of interviews with experts who have fought outbreaks of diseases such as bird flu, swine flu, AIDS, yellow fever and Ebola.

Dr. Carlos Costa, doctor of tropical medicine and president of SBMT, believes the author is right to consider the possibility of a pandemic originating from wildlife. “Although deeply damaged by man, forest ecosystems are still abundant with wildlife and zoonoses that, eventually, may make contact with humans”, explains Dr. Costa. This contact can occur in several ways, such as working in or visiting wild places, for example.

Costa points out that viruses are very plastic, adaptable and transmit rapidly. “Cities are currently heavily populated. There is a great interaction of people indoors, and in precarious living conditions, especially in tropical cities”, he says.

In the opinion Harvard trained doctor, conditions are favorable for the occurrence of an epidemic. “We do not know when or where, but it is a very reasonable possibility”, he notes. Current conditions, especially the high level of interaction between people and international travel, favor the quick spread of a disease. “People who are still in the incubation period, patients, those who are indoors, inside these aircraft, as well as hospitals that are not always prepared to receive this type of emergency”, he says. Although he does not believe this epidemic will be restricted to tropical countries and populations, he does note that tropical cities are much more vulnerable, especially their slums.

Viruses spread easily
“Imagine, for example, the environment of a shopping mall, an airplane, a bus, a subway; the possibilities for dispersion of parasites and viruses by air are rife, mainly from respiratory infection”, says Dr. Costa. He believes it is impossible to predict which mutations will occur in a pathogen that will facilitate its adaptation to humans. According to him, depending on the mutation, this transmission may be through respiratory airways or other routes.

Costa thinks that this is a possibility that will always exist. “When most of humanity lived in the countryside, our interaction with the environment was more profound. Humans hunted, planted and fed themselves. These days, with mechanized agriculture and capitalist exploitation, this has decreased slightly. But in the niches of family and subsistence farming, the interaction with the wild remains”, he highlights. He believes that the most likely location for an outbreak is in a city.

Potential reservoirs
Primates, rodents and bats are reservoirs of disease, according to Quammen. “They are potentials, but there are others”, explains Dr. Costa. “The genomic proximity of monkeys to humans means that some pathogens jump more easily from these species, as happened with HIV. Bats, due to the huge variety of species, may also be vehicles, as well as rodents due to their proximity to people”, he says. He adds that where there are humans there are rodents, primarily, the house mouse.

Although vertebrates are reservoirs that can transmit viruses directly to people, he warns that we must not forget insects. “Aedes aegypti is an example. The occurrence of West Nile Encephalitis across theUnited States, also shows that even in developed nations such epidemics can become uncontrollable”, he warns.

Collective solution
“The world is a global village. It has its backyards, its niches of poverty, but there is hardly a place that is unreachable, unobtainable. So we need to create schemes and ensure that large health surveillance laboratories are attentive”, defends Costa. He says we cannot expect poorer countries that lack scientific and technological competence to monitor these emerging diseases. He says this is a global problem, and as such all nations must work on it.

Although Quammen mentionsChinaas having a promising future, Costa retorts that this is just one example of an emerging nation. “BrazilandIndia, perhaps, are better examples of countries with great scientific competence”, says Dr. Costa, who claims thatBrazilis already showing clear signs of entering a period of scientific Enlightenment.

Costa says that nowadays there are reasonable funds for science, technology and education. “We are hoping that the newly discovered oil [from the pre-salt layer] will also boost resources for this field”, he confesses. He thinks that the Science Without Borders Program will have a positive effect on the Brazilian scientific community in terms of its level of competence and international competitiveness.

“LikeChina,Brazilis the prototype of a scientifically and technologically developing nation, and as a tropical country we are even better equipped to address tropical dilemmas, including the emergence of new diseases”, concludes the doctor of Tropical Medicine.…