Yellow fever deaths are spreading beyond emergency areas.
The Health Department of Minas Gerais released a report indicating 38 deaths from yellow fever in the state; two of the deceased lived in cities outside the areas considered to be under emergency alert; of the 393 suspected cases, 67 were confirmed – there were 58 previously.
Mines 247 - The Health Department of Minas Gerais released a report on Tuesday (25) indicating 38 deaths from yellow fever in the state. Two people who died lived in cities outside the areas considered to be in emergency. Of the 393 suspected cases, 67 were confirmed - there were 58. The patient's place of residence does not necessarily mean the place where they were infected by the disease.
One of the confirmed deaths is of a resident of Januária, in northern Minas Gerais. The other occurred in Delfinópolis, in the south. An additional 45 deaths are still under investigation, in addition to the 38 confirmed monkey deaths in 88 cities across various regions, including Ribeirão das Neves, in the metropolitan area.
Confirmed cases were defined as those that presented with a detectable laboratory test for yellow fever, a non-detectable laboratory test for dengue fever, a vaccination history (unvaccinated/vaccination unknown); signs and symptoms compatible with the case definition; and complementary tests that characterize renal/hepatic dysfunction.
Authorities are investigating the link between the yellow fever outbreak and the collapse of the Fundão dam in Mariana, in the central region of Minas Gerais, in November 2015.
Read the report from Agência Brasil:
A group of experts from different states in Brazil is working together to investigate the relationship between the yellow fever outbreak and environmental degradation. They believe that with more knowledge about the subject, the sudden spread of the virus from time to time could be prevented.
The yellow fever outbreak in Minas Gerais has already caused 38 confirmed deaths in 2017, according to the most recent epidemiological bulletin from the Minas Gerais Health Department (SES-MG), released yesterday (24). Another 45 deaths are under analysis.
Caused by a virus from the family flaviviridaeYellow fever is a disease that occurs in outbreaks, suddenly affecting groups of monkeys and humans. The reasons for this behavior of the disease are not yet well understood. But experts consider the influence of the environment to be certain. According to Sérgio Lucena, primatologist and professor of zoology at the Federal University of Espírito Santo (UFES), the yellow fever outbreak is an ecological phenomenon.
The disease is transmitted in rural and wild areas by mosquitoes. haemagogusIn urban areas, it can be transmitted by Aedes aegyptiThe same virus that transmits yellow fever is present in Brazil as in dengue fever, Zika virus, and chikungunya fever. However, there have been no records of yellow fever transmission in urban areas in Brazil since 1942. In the current outbreak, none of the confirmed or suspected cases in Minas Gerais are urban.
Sérgio Lucena explains that the yellow fever virus is established in some forests and wild regions with low incidence. Suddenly, for some reason yet to be discovered, it spreads rapidly, affecting monkeys and humans. The animals begin to die first. "They are sentinels. If the virus begins to spread in a certain area, the death of the monkeys will send us an alert," he explains.
According to the primatologist, Brazil could have a well-organized system to anticipate outbreaks, but there is no investment in this area. If there were more knowledge, Minas Gerais, for example, could have started the vaccination campaign earlier in the municipalities within the at-risk area, reducing the spread of the disease. Vaccination is the main measure to combat yellow fever.
Forests
Last week, experts studying yellow fever from an ecosystem perspective met in Belo Horizonte at a seminar organized by the Renova Foundation, linked to the Samarco mining company. During the event, they reviewed all current knowledge on the subject, aiming to take a first step towards changing the current situation.
One of the researchers' hypotheses is that deforestation over the years has left monkey species in very small fragments of forest, which has several consequences. "Impoverished ecological systems can favor the growth of mosquito populations. Infected mosquitoes finding large populations of monkeys in isolated patches of Atlantic Forest may be the origin of these outbreaks," warns Sérgio Lucena.
Scientific evidence also suggests that healthy forests, with high biodiversity, would hinder the proliferation of viruses. Although outbreaks can still occur, their intensity may be lower in a preserved environment. This is explained by Servio Ribeiro, a biologist and professor of ecology at the Federal University of Ouro Preto (UFOP).
According to the researcher, with each outbreak, the monkey population is significantly reduced and recovers slowly in the following years. "A new outbreak likely occurs when the virus finds monkeys in nature with the right number, conditions, and genetic characteristics. And when there are many infected animals, it's easy for the disease to reach humans," he explains.
A forest with a greater availability of fruit and shade, and where there is no pollution, allows monkeys to develop healthier and without stress, with a more efficient immune system, offering greater resistance to disease. Servio Ribeira points out that genetics also plays a role.
"During periods when the virus is rare, monkey populations reproduce without this selective pressure. This means that, for a period of years, being resistant or not to the yellow fever virus is not a factor that changes the reproductive success of the monkeys. However, living in small fragments of forest, without corridors connecting the woods, these populations grow with relatives interbreeding. In this way, the individuals are very genetically similar. When a virus reaches a monkey in a population without genetic diversity, it spreads rapidly."
For this reason, the existence of corridors connecting the forests can help contain yellow fever. Through these corridors, groups of monkeys can mix. Interbreeding between distinct groups would lead to the exchange of genes and create populations with greater genetic diversity. In this context, a spread of the virus would be less likely to cause yellow fever in many monkeys at once.
Mariana tragedy
Other lines of research aimed at elucidating the reasons that lead to the start of each outbreak seek to understand whether changes in forest areas are exposing people to infected mosquitoes and whether climatic factors favor the growth of the mosquito population.
On the other hand, Servio Ribeiro considers the possibility of the Mariana (MG) tragedy influencing this yellow fever outbreak in Minas Gerais to be remote. Some of the municipalities affected by the disease's circulation are located in the Rio Doce Valley. A portion of the 60 million cubic meters of tailings released in the collapse of the Samarco mining company's dam in November 2015 flowed throughout the Rio Doce and reached the coast of Espírito Santo.
"Yellow fever is a disease of the interior of the forest. The mosquito that transmits it lays eggs in tree cavities and bromeliads. It is a mosquito of the forest structure. It doesn't relate much to large bodies of water and rivers. The cities affected by the disease are in a region where the tailings didn't arrive with enough force to destroy the forest," says the biologist.
According to Servio Ribeiro, the hypothesis would be stronger if the outbreak had occurred near Mariana (MG), where the impact of the tragedy was more aggressive and led to deforestation. "In the Rio Doce Valley, this tailings accumulated on the banks. Of course, there is degradation. But this degradation, based on our knowledge, should not be affecting the relationship between the vectors and the monkeys inside the forest," he added.
Endangered species
According to the SES-MG epidemiological bulletin, there are 18 municipalities with monkey deaths under investigation. Another 70 report rumors of deaths among the primates. For Sérgio Lucena, these data do not convey the full extent of the animal mortality. "Monkeys are dying in large numbers. I was with a team of researchers in the rural area of Caratinga (MG). We walked in the forest, talked to people, and confirmed the high mortality rate," he says.
According to the primatologist, the phenomenon began in Minas Gerais, but is already occurring intensely in Espírito Santo. The situation puts endangered species at risk, such as the muriqui monkey. However, the most affected are the howler monkeys. According to Sérgio Lucena, studies conducted during the 2009 outbreak in Rio Grande do Sul showed that howler monkey populations were reduced by 20%. "While seven people died that year, about 2 monkeys perished," he states.
The researcher points out that howler monkeys are precisely the biggest victims of yellow fever. "They are highly susceptible to the disease, unlike humans. In the human population, few people develop a severe case and many infections are asymptomatic. The person doesn't even know they contracted the virus," he explains.
One concern raised by the state's Health Department relates to violence against monkeys, recorded in some municipalities. This is because some people believe that sacrificing the animals can help prevent the disease in humans. The agency published on its website... blog A post aims to demystify this idea and clarify that animals are, in fact, allies that help map the disease. "The viral infection lasts only three to five days. After that, the monkeys die or become immune. Therefore, attacks generally target healthy animals that have not had contact with the virus or that are already immune and do not pose a risk," the text adds.