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Source: https://www.scidev.net/america-latina/news/dengue-avanza-en-brasil-en-areas-que-estaban-protegidas/
12/20/21
Dengue advances in Brazil in areas that were "protected"
The area of dengue transmission in Brazil has changed in the last decade
Vector control should also focus on areas at risk of future outbreaks.
Other Latin American countries, such as Argentina and Peru, are also experiencing a similar situation.
By: Renata Fontanetto
Certain areas of Brazil that were previously protected by geographic barriers to the transmission of dengue — such as remote locations in the Western Amazon, high-altitude points in the Southeast, and southern regions — are now at higher risk.
This is suggested by research published in the journal Plos Neglected Tropical Diseases that studied the spread of dengue outbreaks in Brazil to understand what is accelerating the spread of the disease.
The study's finding reinforces the importance of monitoring for public managers to design prevention strategies, knowing the areas where dengue has already been detected and are at risk of future outbreaks.
According to the research, climate change, global mobility and increasing urbanization are factors that contributed to the global incidence rates of the disease doubling every decade for 30 years.
The analysis collected data from January 2001 to December 2020, used a statistical model that calculated different variables, and used monthly dengue case notifications for the 5,570 Brazilian municipalities.
In addition, they recorded the monthly average temperatures of each studied locality, the percentage of inhabitants who lived in urban areas in each decade and the mobility of people according to each city by size and link with other localities.
“In areas that have not had previous outbreaks, people do not have immunity to the virus. If this is the first time the virus has been present in the area, residents are particularly at risk, ”says Sophie A. Lee, first author of the research and scientist at the Center for Mathematical Modeling of Infectious Diseases at the London School of Hygiene & Tropical Medicine.
The study warns because the four serotypes of the dengue virus are endemic to Brazil and, as it has a tropical and subtropical climate, there are favorable conditions for the transmission of the virus through its best-known vector, the Aedes aegypti mosquito, which is very present in regions urban. To reproduce and transmit the virus, the insect needs temperatures between 17.8 and 34.5 ° C.
There is also another common species in rural environments, Aedes albopictus, which, according to other research, may be involved in the introduction of dengue in these areas. This species prefers lower temperatures (between 16.2 and 31.4 ° C).
By observing how many months of the year each municipality had an average temperature between 16.2 and 34.5 ° C, they evaluated whether the temperature influenced changes in the area of dengue transmission.
The results indicate that the geographical transmission barrier has changed in the last decade. In the south, the states of Paraná and Santa Catarina entered the transmission area. In the north, the states of Acre and Amazonas are at higher risk of outbreaks and, in general, the geographical limits of the region have practically disappeared.
According to the research, "municipalities that had already experienced an outbreak were twice as likely to have subsequent outbreaks." In terms of connectivity and mobility, the study identified that cities "with many transport connections increased the chances of an outbreak", since the mosquito could be transported or a traveler could be infected with the virus.
“Dengue transmission barriers are eroding very rapidly. I hope that the results can inform public policy, because vector control should focus on areas at risk of future outbreaks, as well as areas that are already known to have outbreaks, to try to avoid future expansion, "warns Lee.
12/20/21
Dengue advances in Brazil in areas that were "protected"
The area of dengue transmission in Brazil has changed in the last decade
Vector control should also focus on areas at risk of future outbreaks.
Other Latin American countries, such as Argentina and Peru, are also experiencing a similar situation.
By: Renata Fontanetto
Certain areas of Brazil that were previously protected by geographic barriers to the transmission of dengue — such as remote locations in the Western Amazon, high-altitude points in the Southeast, and southern regions — are now at higher risk.
This is suggested by research published in the journal Plos Neglected Tropical Diseases that studied the spread of dengue outbreaks in Brazil to understand what is accelerating the spread of the disease.
The study's finding reinforces the importance of monitoring for public managers to design prevention strategies, knowing the areas where dengue has already been detected and are at risk of future outbreaks.
According to the research, climate change, global mobility and increasing urbanization are factors that contributed to the global incidence rates of the disease doubling every decade for 30 years.
The analysis collected data from January 2001 to December 2020, used a statistical model that calculated different variables, and used monthly dengue case notifications for the 5,570 Brazilian municipalities.
In addition, they recorded the monthly average temperatures of each studied locality, the percentage of inhabitants who lived in urban areas in each decade and the mobility of people according to each city by size and link with other localities.
“In areas that have not had previous outbreaks, people do not have immunity to the virus. If this is the first time the virus has been present in the area, residents are particularly at risk, ”says Sophie A. Lee, first author of the research and scientist at the Center for Mathematical Modeling of Infectious Diseases at the London School of Hygiene & Tropical Medicine.
The study warns because the four serotypes of the dengue virus are endemic to Brazil and, as it has a tropical and subtropical climate, there are favorable conditions for the transmission of the virus through its best-known vector, the Aedes aegypti mosquito, which is very present in regions urban. To reproduce and transmit the virus, the insect needs temperatures between 17.8 and 34.5 ° C.
There is also another common species in rural environments, Aedes albopictus, which, according to other research, may be involved in the introduction of dengue in these areas. This species prefers lower temperatures (between 16.2 and 31.4 ° C).
By observing how many months of the year each municipality had an average temperature between 16.2 and 34.5 ° C, they evaluated whether the temperature influenced changes in the area of dengue transmission.
The results indicate that the geographical transmission barrier has changed in the last decade. In the south, the states of Paraná and Santa Catarina entered the transmission area. In the north, the states of Acre and Amazonas are at higher risk of outbreaks and, in general, the geographical limits of the region have practically disappeared.
According to the research, "municipalities that had already experienced an outbreak were twice as likely to have subsequent outbreaks." In terms of connectivity and mobility, the study identified that cities "with many transport connections increased the chances of an outbreak", since the mosquito could be transported or a traveler could be infected with the virus.
“Dengue transmission barriers are eroding very rapidly. I hope that the results can inform public policy, because vector control should focus on areas at risk of future outbreaks, as well as areas that are already known to have outbreaks, to try to avoid future expansion, "warns Lee.
