MoroniSorroche
Environmental Factors Determining the Rise of Acute Respiratory Infections in Tropical Fortaleza Brazil?
Introduction
This study was done for the determining and understanding of the factors and the prevalence of the seasonal pattern of Influenza infections for the city of Fortaleza, capital of the state of Ceara in Brazil.
Fortaleza is a city with 2,250,000 inhabitants at sea level, 4 degrees south of the Equator, with a tropical weather and with two very dissimilar seasons: the rainy season which is mostly characteristic of the first half of the year, usually from January to May, and the second half is the dry season when there is virtually no rain for most regions of the state. There is an unvarying high humidity level of 70% all year round. Rain in Fortaleza occurs regularly for short periods of 3 or 4 months, with weekly and daily variations in intensity of precipitation.
Because of the possibility of epidemic (and even pandemic), there is a great need of emphasis on observation and procedure of treatment. Influenza is in terms of respiratory viruses, the one that poses the utmost threat to the public of Fortaleza. Information on epidemiology of Influenza is of great prominence for the planning and prevention of the virus spread, and the measurements are to be considered based on the geography and other factors that would otherwise be conducive to the spreading of Influenza.
The center for the study was the Hospital Infantil Albert Sabin (HIAS), a public teaching hospital that serves the low-income families in the community. The study was conducted from the years of 2001-2007, (January of 2001 to December of 2007) on children and kids from 1 month of age up to 16 years of age who came to the HIAS and attended ambulatories, emergency rooms and wards with complaints of ARI within 7 days of onset.
Methods
The method used to detect the condition of the patients was by indirect immunofluorescence assay, performed on the nasopharyngeal aspirates collected from the pediatric out-patients with a suspicion of an ARI. Influenza virus was detected in 234 of the 3,708 specimen taken.
Sampleswere collected from Monday through Friday by a medical student who stayed at the hospital during 4 hours for each collection. Parents of the patients were informed of the study taking place, and then provided consent in accord with the Research Ethics Committee of the HIAS.An average of 10 specimens was collected per week.
The samples were observed and screened for influenza A and B, adenovirus, respiratory syncytial virus (RSV), and Para influenza viruses 1, 2, and 3 using an indirect immunofluorescence assay (IFA) which was implemented using the Respiratory Panel I Viral Screening and Identification.
The influenza season in Fortaleza, for the study, was determined to be in bloom when the positive samples being tested were more than 10%. The rainy season was determined to be the consecutive months that represented 70% of the year round volume of rain, with the beginning of the rainy season being the month when 10% or more of the year’s total rain volume occurred.
Results
From the samples taken through those 7 years, a total of 1,089 (29.3%) samples were positive for at least one of the viruses screened for and 234 accused positive for influenza type A, (89.3%) and B (10.7%). For all the years of the study, influenza A and B were going around during the same months with A being predominant by the same ratio compared to B, except for 2006 when A was the only type circulating. Among the considered viruses, influenza was the second-most frequently found, RSV being the most detected in all years of the study.
Most of the patients (61.5%) being tested showed infection of the upper airways. The median age of the same was 34 months, recalling that the age group was 1 month to 16 years of age. The gender sharing was 51.3% (120 people) male and 48.7% (114) female.
The influenza season in Fortaleza lasted from 1 to 4 months. Interestingly, in 2003, all cases of influenza occurred in the month of April. 94.4% of the overall yearly detection of the virus happened in the first half of the year. Of the remainder period, cases were detected only in July 2004, 2006, 2007 or September 2001, 2004, 2005, 2006 (only in 2007 was influenza season still in effect, all others were sporadic cases in the second half of the year.)
The peak of the season of influenza occurred from February to May, when 88.8% of the cases were confirmed.
Although there were variations of the rainy season with the status of the influenza season, evidence does show that there is a relation of the seasonal spread of ARI, especially of influenza and RSV, with environmental conditions. In temperate climates flu infections are marked at a low throughout the year, but rises greatly during the cold months of winter. In Fortaleza with its tropical weather and 70% humidity, the peak periods of the flu are definitely associated with the rainy season which was from February to June, inside these months, 93% of the cases were observed.
Interestingly again, the years of 2003 and 2005, 100% and 74% of the cases were observed in the fourth month of the rainy season. For 2002, 2004, 2006 and 2007 the cases did not come until after the first month of the rainy season had passed, and not one year of the study showed a single case of the flu appearing before the beginning of the rainy season. It was also observed that the flu seasons were always shorter than the rainy seasons.
A possible explanation for the random detectionof the virus in July and September is the entry of tourists from southeast and south regions of Brazil to visit Fortaleza, (influenza peak in those regions being between June and August), representing potential sources of the virus at a different location and at apparently irregular times of the year.
Conclusion
Until this study, there was nothing substantial yet done concerning the study of season trends of the spread of influenza in the city of Fortaleza in Brazil. The fact that the study included likewise consideration of influenza in upper and lower respiratory airways of patients allowed the group of researcher to eliminate biases in the selection of patients to be studied. It was clear that in the first half of the year, representing the rainy season, there was a greater number of visits from patients being seen for ARIs, not necessarily influenza. The study confirmed previous data that RSV contributes to that higher number of visits during that period.
Because of unestablished data from the rest of the northeastern regions of the country, there cannot be a safe determining of the pattern of influenza as of yet, although intraregional variations are shown. With studies in other northeastern states like Bahia and Alagoas being conducted, there may soon be an elimination of some hypotheses (and confirmation of others) as these surveys are publicized.An accepted theory right now about the pattern is the climate variation and humidity, plus climatic variables with a narrow range in Fortaleza. Evidence also addresses the Hope-Simpson model which considers the forming of vitamin D in the skin, by ultraviolet B radiation from the sun. To briefly explain, this phenomenon has an effect on the innate immunity of the individual which proves to play animportant role in protecting the respiratory tract from infections. The decrease and impairment in the synthesis of vitamin D3 for individuals in temperate regions comes about during the seasons when hours of sunlight are reduced also. There is still need for a study on the impact of the rainy season, the reduction on sunlight, UVB radiation, and vitamin D synthesis in tropical regions like Fortaleza.
All these studies contribute to the understanding of the seasonality of influenza in primarily Fortaleza, but also of the entire country of Brazil; with it, the complexity of the problem and the factors to be monitored of intra and inter-regional range.
In Addition
Immunofluorescence Assay seemed to be effective in the determining of which virus is present in the patient at the time of diagnosis, and it seems that determinacy and testing for several kinds of viruses, as opposed to testing for just Influenza, isn’t any sort of deterrence for the efficiency of the study. In the article it is mentioned that there are similar studies going on still in the states of Bahia and Alagoas. I’m uncertain of how revealing these studies can be since neither Bahia norAlagoasshare immediate borders with the state ofCeara(though they do lie close to each other). I think those states were chosen for the study because of the size of their capital city and readier medical assistance, although poorer and less accessible regions in between should be considered just as important. I feel that to get better and more accurate results, much need to be implemented. A similar and simultaneous study of the surrounding region should be done. There needs be coinciding observance for the virus in all the big cities in the northeast of Brazil, and to also take into consideration the smaller cities too. There needs to also be an awareness of how much of the population does not seek medical attention and how they are treating these conditions from home without expert assistance. However minimal, these number should also contribute to showing the level of prevalence of the virus.
Another suggestion for future consideration I think could be door to door sample collection and treatment by an expert, or surveyor that is able to determine with few mobile resources if the virus possibly exists in the sick of these poor surrounding small cities, thus conveying treatment to the patients.
This choice of article for me is in part because I am from the country of Brazil and because I am interested in understanding how the passing on of viruses from person to person happens. It is exciting to learn the differences in patterns due to regional climates and the weather, and geographical factors that contribute to the spread of ARIs, or of any other disease for that matter.
Figure 1.Monthly detection of influenza infections by year of study.
Figure 2.Monthly occurrence of acute respiratory infections caused by influenza viruses and rainfall in Fortaleza, Brazil, from January 2001 to December 2007.