CLIMATE CHANGE, WEATHER TYPES AND DENGUE: a comparative
approach between Giruá (RS) and Maringá (PR) – Brasil.
MENDONÇA F., ROSEGHINI W.F.F., AQUINO JUNIOR J.,
Laboclima – Laboratory of Climatology – Department of Geography - UFPR /Curitiba, Paraná, Brazil.
chico@ufpr.br, feltrim@hotmail.com, zeaquinoju@yahoo.com.br.
Dengue is currently one of the most important worldwide public health problems. It is a disease of the tropical
world, in which most of Latin America is located, that provides ideal conditions for the Aedes mosquito (aegypti
and albopictus) in its physical and natural environments (particularly climate) in association with the sociocultural environment (urbanization and lifestyle) and the ineffectiveness of public health policies, resulting in
severe epidemics of the disease. The scenarios that predict the intensification of global warming, along with the
acceleration of urbanization in the South, make up a disturbing reality with regards to dengue control. The main
consequences of environmental change will significantly affect urban populations, introducing an urgency to
create institutional mechanisms able to cope with the forms of adaptation and mitigation of environmental
impacts, especially when considering the most vulnerable populations. Although several studies suggest that the
effects of environmental change tend to focus more on cities, because of the intensity and forms of urbanization,
the assessment of socio-environmental dynamics contributes to the identification of areas where there is greater
vulnerability and risk. In this context, this research turns to the analysis of the expansion of risk areas for dengue
fever in southern Brazil. A major objective is to highlight the favorable climatic conditions for the manifestation
of dengue epidemics and spread of this disease in the region. Among the counties selected for the study, the
following were highlighted: Giruá (RS), a city in which the onset of reported cases is very recent in a region
considered environmentally limiting to the development of the vector; and Maringá (PR), a city with a high
number of reported cases due to severe epidemics in recent years, and distinguished by a large influx of people
and products on interstate and inter-municipal scale. With regards to climate analysis, Rhythmic Analysis
techniques proposed by Monteiro (1976) were applied. On issues related to climate dynamics, this study showed
that high temperatures light winds and intermittent rain, especially during spring and summer, are the main
social and environmental conditions responsible for the outbreak of dengue epidemics. One important result of
this study was the identification of three particular weather types favorable for the breeding of the vector (I), the
transmission of the disease (II) and the outbreak of the epidemic (III), by comparing the problem in both cities
analyzed. Besides climatic factors, other social and environmental constraints were identified for the
development of dengue epidemics in the two cities, thus proving the multiple causes of disease; among these
elements are: the mobility of the population (inter and intra-flow intensive urban commuting), the circulation of
serotypes (on a local, national and international scale), the general way of life conducted by the population
(consumption and disposal of solid waste), the inefficiency of public policies (control of the problem and
programs to combat the disease), the indifference to situations of risk and vulnerability to the disease, in addition
to the already chronic local and country-wide concentration of wealth. An important point to highlight is that,
even in different cities, the epidemics and the series of weather types occurred in a similar way, emphasizing the
importance of detailed studies on both temporal and spatial scales. Finally, this research aims to assist the health
sectors in understanding and improving disease control actions.
INTRODUCTION
Dengue, arbovirus transmitted by mosquitoes of the genus Aedes, with predominance in many
countries, especially in tropical countries, is one of the most important epidemic diseases today.
It is an infectious disease caused by a virus of the family Flaviridae, Transmitted by the
mosquito Aedes aegypti. His infection is caused by 04 serotypes of flaviviruses: DEN-1, 2, 3 and 4,
which produce serotype-specific immunity. Can the disease manifest itself in the classic form, dengue
hemorrhagic fever or dengue shock syndrome, the latter being the two most severe forms, which can be
fatal. (BRAZIL, 2011)
In Brazil, there are reports of outbreaks of dengue since 1846, but the first Evidences are from
1982, when were DEN1 and DEN4 serotypes isolated in BoaVista (RO). The introduction of these
serotypes in Brazil took place by land, coming from the Caribbean and northern South America has not
spread this epidemic to other areas because the mosquito Aedes aegypti was not dispersed. The DEN-1
was reintroduced into Brazil in 1986, having been isolated in New Delhi. That year there were
notifications 33.500 and the following year, 60.000. From then on dengue began to dissipate a large
part of Brazil territory. (BARRETO & TEIXEIRA, 2008, apud Donalísio, 1995).
With the introduction of serotype DEN3 in 2001, the result was an epidemic of more than
385,000 cases and 700,000 the following year. In recent years, intense epidemics stood out. In 2007
just over 450.000 cases, approximately 560.000 notifications in 2008 and 2009 more than 400.000.
(SINAN, 2010).
In Brazil, the disease currently develops in all states, and the appearance in the South and the
rise of the case numbers has been intensified in the last decade. Specifically in the States of this region,
from the late 1990s on, some municipalities started to record outbreaks of the mosquito infestation and
consequently positive autochthonous cases of the disease. According to Mendonça (2009), the first
records of autochthonous cases date back to 1993 and epidemics began to happen after 1995. Over the
past 10 years, there are the epidemics of 2003 and 2007 that reached nearly 9,500 cases and 45,000,
respectively.
According to Mendonça (2009, p. 36), climate becomes a major epidemic constraint in this
region, because the "occurrence of most indigenous and imported cases of dengue in the South shows a
seasonal behavior of the disease, with the biggest records in March and April, "unlike other states in the
rest of the country, which can display cases throughout the year. There is, in this example, the
importance of climatic aspects, since, according to the author, the occurrence of dengue notifications at
the end of the summer season may be associated with the accumulation of heat and humidity.
It is noteworthy that until the early 1990s, the state of Parana, located on the North of the
southern region of Brazil, was considered to limit the advance of dengue to the South of the country,
but cases are being registered in northern Argentina.
From the perspective of developed through Health Geography, this study analyzes, in specif
cases and by comparison, the social and environmental conditions from two cities in southern Brazil:
Maringa, located in the north of Parana State, and Giruá, located in the northwestern state of Rio
Grande do Sul (figure 01).
Figure 01: Maringá and Giruá – Location of the municipality, States of Paraná and Rio Grande do Sul.
Maringa and Giruá are located in a transition region between the tropical superhumid with no
semi-drought and super humid without drought (IBGE, 2010). They have annual average temperatures
between 17 and 22ºC, with absolute maximum above 30°C and absolute minimum below 5°C. The
relative humidity is around 70% with precipitation between 1500 and 1700mm.
According to IBGE (2010), Maringá has approximately 357,117 inhabitants; its economy is
geared to the farming sector, mainly from soybeans.
The appearance of positive cases reported Maringá dengue is currently in a major public
health problem in the municipality. Within the urban perimeter of Maringá, an outbreak in 2002
reached 637 confirmed cases, followed by two years with a decrease in occurrences, when in 2004
were only five confirmed cases. In 2005 there was a further increase of cases followed in 2006 which
added a total of 199 confirmed cases. In 2007, an epidemic totaled more than 8000 confirmed cases, of
those, with record of two deaths (AQUINO JUNIOR, 2007).
On the relationship of dengue fever and climate variability, the notifications of the disease
during the periods from 1995 to 2000 and 2002 to 2006 had direct relations with the temperatures,
when the number of positive cases reported increased by months of high temperatures and frequency of
rainfall.
Giruá, with 17,139 inhabitants (IBGE, 2010), located in the northwestern state of Rio Grande do
Sul , 490 km from Porto Alegre, is predominantly rural.
Although the number of dengue cases in Giruá are not considered to be high compared to other
municipalities, the city was chosen among others because it presented the highest incidence rate of
dengue in 2007 in Rio Grande do Sul, with the equivalent of 1500 notifications for every 100 thousand
inhabitants, a rate considered high according to World Health Organization In addition, the city prior to
this epidemic was harmless disease, thus justifying the relevance of the study.
MATERIALS AND METHODS
The collection of data related to cases of dengue occurred near the State Departments of Health
of Paraná and Rio Grande do Sul, requested by letters of request in order to formalize the request.
Thus, it was sent by the surveillance team of both States to information regarding cases of dengue. For
the spatial georeferenced notifications, we used the ArcGIS software.
Afterwards, a more specific study was made about the elements that characterize the climate of
the South, which also sook a theoretical and methodological base that enabled the detailed analysis of
the climatic characteristics in agreement with data from reporting cases of dengue epidemic period
from March to May of 2007, based on Monteiro’s rhythmic analysis model (1971).
According to Monteiro (1971), the method of analysis allows a sense of rhythmic momentum
climate, and uses the analysis of daily climate data/time elements such as temperature, atmospheric
pressure, precipitation, relative humidity, prevailing weather systems, wind direction and speed.
However, for this research used only one approach adapted to the pace of climate study, which
considered the study of weather elements in the daily scale associated with the data of dengue
notifications, allowing a sense of place and climate dynamics of the epidemic.
RESULTS
Dengue in Maringá
The epidemic episode occurred between 2006 and 2007 recorded a total of 7,919 dengue cases
and within these, 3,512 cases were male and 4,407 female. It was confirmed the seasonal pattern of
disease in the area, because it focused during the months January to May, both caused the outbreak in
2006, and for the epidemic occurred in 2007. The months of March and April are still characterized as
a risk because they are the focus of dengue notifications.
From December to late February, a period regarded as the beginning of the epidemic episode,
Maringá recorded a total of 794 positive reported cases (figure 02). Only in February were reported 734
dengue infections, demonstrating the rapid growth in the number of cases. This fact showed high
mosquito infestation and spread of the virus.
Figure 02: Maringá, 2007 - Dengue Cases - Dec/2006 to Feb/2007
Source: SINAN. Organization: Aquino Junior, J.; Marangon, FHS
During March, the number of records of dengue rose more than 68% over the previous month.
In March were recorded as positive a total of 2,341 dengue cases.
The epidemic peak was identified in April, when the city reached the highest values in
infection and transmission rates. The development of the epidemic during the months of March and
April shows the spread of disease throughout the perimeters of the municipalities surveyed. However,
the disease was characterized by the most densely populated neighborhoods and low income as the
highest risk of dengue infection.
Just as the beginning of the epidemic, its end was also quick. During the month of May, the
number of new cases fell from 3478 to 1202, a decrease of 34% compared to the previous month. From
May to the month of June fall in the number of new cases has been more abrupt, as throughout the
month were recorded only 98 cases, overcoming a fall of 90%.
On the rhythmic analysis of the epidemic occurred in 2007 in the city Maringá, confirmed the
seasonal pattern of disease in the area, because it focused during the months January to May, both
caused the outbreak in 2006, and for the epidemic occurred in 2007. The months of March and April
are still characterized as a risk group because it is there that the focus of dengue notifications.
Concluded that the average and maximum temperatures were favorable to analyze the rise of
cases and epidemiological peak performance. Since the minimum temperatures were used as a
parameter of analysis for the development environment to limiting mosquito breeding. Importantly, the
high number of cases the disease runs in proportion, the temperature variations recorded in local and
regional scale.
Another climatic element that served as a useful tool in studying the determinants of the
disease was rainfall. It was evident that the hot months of the rainy season (December and January)
have become essential for mosquito infestations.
For the spreading of dengue vector, concentrated rainfall in March and April was important
because combined with the temperature, served as agent’s maintenance of the biological cycle of
A.aegypti. It is noteworthy how the intermittency factor of rainfall -- with a concentration of rainfall at
intervals of 3 to 10 days at the end of the rainy season -- makes a good indicator for the formation of an
excellent environment for mosquito breeding.
Using the rhythmic approach (figure 03) to analyze of the peak months of the disease and ,
climatic conditions varied on following cycle: entry of Atlantic tropical mass with sunny days followed
by continental equatorial mass and succeeded by the arrival of the cold front. In the days of the cold
front, concentrated rainfall and small drops in temperature have focused on the reduction of dengue
cases in the study area.
Figure 03: Maringá, 2007 - Dengue cases and types of climate.
Source: ECPM / SINAN. Organization Aquino Junior, J.; Roseghini, WFF
The role of mass Tropical Atlantic, with sunny days and days of intermittent rains
concentrated, became major factor for the manifestation of dengue. On the other hand, the performance
of cold fronts and mass Polar Atlantic influenced the biggest decreases in temperature and these, in
turn, caused the decrease of the records of new cases.
Dengue in the town of Giruá
In 2007, 215 cases were external, and the large majority of reports (around 80% of cases)
occurred in April, when there were 174 confirmed cases, according to data from SINAN (2010). Even
with a number of reports much smaller compared with the city of Maringa, the epidemic period was the
same, thus demonstrating the seasonality of the disease.
According to a document sent by the 14th Health Regional Coordination, health surveillance
division, the municipality showed an average of 0.89 of infestation rates (IIP) of Aedes aegypti in 2007.
As Aquino Junior affirms (2007), IIP "it is the percentage of households with the presence of the
mosquito that transmits dengue based on the total number of houses visited in order to investigate the
presence of the mosquito and the magnitude of this presence." According to the same author , "the
PNCD (National Dengue Control) characterizes the strata or counties with rates below 1% as being at
low risk for spread of dengue, medium risk between 1.1% to 7.9% and high risk above 7.9%. "This
means that the city has low risk of proliferation of the vector.
In the distribution of autochthonous dengue cases in 2007 (figure 04), the red dots mark
notices within the city of Giruá, the blue dots are the result of cases outside the city limits of the city. It
should be noted, however, that some cases were not scored as they occurred in the same place doing the
overlay, which does not favor the display cases.
Figure 4: Giruá, 2007 - spatialization of reported dengue cases;
Org Marangon, FHS and Cordero, UD
Analyzing the image and based on the city plan (Giruá, 2010), it is clear that there was a greater
concentration of cases in Residential Zone, specifically in Hortêncio District (highlighted). This
district, located in the eastern city, is at the limit of the urban area and has at least 04 high-risk areas of
infection, for example, junkyards and abandoned buildings. It was in this region, even where the first
cases were reported native of the year. Importantly, some points were located near a road linking the
city to neighboring cities. In other words, there may be an influence of inter-city movement, because of
this road.
With regard to climate, and with some analysis of weather data (FEPAGRO) State Foundation
for Agricultural Research (2010) for the year 2007 Giruá, it was found that the municipality provides
optimal environment for the development of the vector. The average minimum temperature was 14.8
C, mean maximum of 24.9 º C and an average of 19.9 º C.
In the monthly analysis of the same data, showed that the maximum temperatures for February,
March and April (30.1 ° C, 29, 1 º C and 26.7 º C, respectively) and rainfall (151.3 mm, 121.3 mm and
160.2 mm, respectively) were favorable for the greatest number of cases in March, and especially in the
month of April, way we perceive the occurrence of cases seasonally in the warmer months of the year.
For the rhythmic analysis (figure 05), according to information Cptec (2010), during the
epidemic period of dengue in Giruá (1 March to 15 May), we observed the performance of three
different air masses: Polar Atlantic Mass (MPA), Continental Tropical Mass (TCM) and Continental
Equatorial Mass (MEC).
Figure 05, Giruá, 2007 - daily climatological analysis of the epidemic period.
Org: Roseghini and Bello, 2010.
In March, there was a predominance of activity of the MTA, with high temperatures. Although
30 cases of dengue have been reported, in March was characterized by providing favorable conditions
for the evolution of the vector, from the egg to adulthood - with temperatures between 25 ° and 29 °
and intermittent rainfall. After the rains that occurred between 10 and 15 March, there was a long
period marked by low rainfall (4.8 mm) and high temperatures (daily average of 20 ° to 30 ° C)
between days 16 and April 2, suitable to development, proliferation and bites result mosquito. As a
result the conditions of March and early April, this month was the highest number of reported cases,
with 15 in 19 days and 173 in total.
The month of April was characterized by being the wettest of the period analyzed, the MPA
was the most active mass especially in the last day of the month, 28 days in the daily minimum
recorded was 07 °C. Between the days 16 and 21 there was a predominance of the MTA, from April
24, the entry of a cold front and an MPA shortly thereafter, primarily caused the decline in minimum
temperatures and can be considered an inhibiting factor vector decreasing the number of bites and
resulting drop in reported cases in May.
During the month of May, the frontal system that stood in Santa Vitória do Palmar, RS, caused
rain on 06 days in 36.4 mm and 32.4 on day 07. This cold front was intense, and this system was
responsible for the first episode of chill and the lowest temperatures of the year in various locations in
Brazil, in 09 days the minimum temperature reached in Giruá 4 °C below the temperature resistance of
the vector.
The analysis of the chart showed that environmental conditions were favorable for the
development of the vector (mosquito from egg to adult) in the rainy period of 09 days, 10 and 15
March, followed by a dry period with temperatures not less than de minims 15 °C.
Upon entry of a frontal system in early April, despite a slight decline in temperatures, the
conditions remained appropriate, characterizing the period conducive to infection and resulting in the
peak notification recorded in the second half of April.
Thus, can be inferred for the city studied, the average and maximum temperatures were
favorable and the rising cases of vector operations. Since the minimum temperatures were used as a
parameter of analysis for the development environment to limiting mosquito breeding.
Social and environmental constraints of dengue
Faced with the problem of dengue installed in southern Brazil, specially its advances in recent
years, this research shows that the climatic seasonality was essential for the maintenance of the disease
epidemic in both cities. An important point to stand out is that, even in different cities, epidemics and
the succession of types of weather occurred in a similar way, explaining the importance of detailed
studies in both temporal and spatial scale.
By comparing the two cities, it became clear identification three types of time responsible for
maintaining the ecology of the dengue vector, the reproduction of the vector (I), transmission of the
disease (II) and the outbreak of the epidemic (III).
The mean and maximum temperatures were favorable to analyze the rise of cases and
epidemiological peak performance since the minimum temperatures were used as a parameter of
analysis for the development environment to limiting mosquito breeding sites.
Another climatic element that served as a useful tool in studying the determinants of the
disease was rainfall. It was evident that the hot months of the rainy season (December and January)
have become essential for mosquito infestations. For the dispersal of dengue vector, concentrated
rainfall in March and April were important because combined with the temperature, served as agents in
maintaining the biological cycle of A.aegypti. Noteworthy is the intermittency factor of the rains. The
concentration of rainfall, with intervals of 3 to 7 or 10 days at the end of the rainy season, features the
work of the MTA, has become a good indicator for the formation of an excellent environment for
mosquito breeding.
Both Giru and to Maringa are worthy of noting that the climate conditions are not the only
factors responsible for the temporal evolution of dengue. It is necessary to think of climatic elements
together with the profile of those infected, among other social and environmental elements. In the
spatial distribution of reports, the epidemic of 2007 showed concentrations of indigenous cases and
outbreaks of these pathways possibly related to inter-municipal access, risk areas established by the
control programs, and the entry of imported cases.
About policies public, the ineffectiveness of dengue control programs, which often act in a
palliative, the lack of planning and optimal resource utilization characterized as the main conditions for
the manifestation of dengue. It is noteworthy local policies in its municipal level, important for
controlling the disease, because through them the resources to fight dengue will be made.
The way of life for residents can also be considered as a condition for the manifestation
dengue, because regardless of the purchasing power of residents, there are differentiations of the type
of treatment that they have with containers that favor the development of breeding of the mosquito
vector of dengue.
Finally, this research aims to assist the health sectors in understanding and improving actions
to control the disease. proposed for public policy and health sectors to develop new studies and disease
control programs that aim not only of the risks of emergency, because there must be an a priori
understanding of the vulnerabilities, particularly when the intention is installed policies for the
prevention of diseases in the long term.
REFERENCES
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município de Maringá, PR, de 2002 a 2006. Monografia – Universidade Estadual de Maringá, Setor
de Ciências Humanas, Letras e Artes, Departamento de Geografia. 2007.
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