Aedes aegypti mosquito poses risks to 885 Brazilian cities

Figures published today (Nov. 24) by the Health Ministry reveal that 855 Brazilian cities are facing alarming risks of an outbreak of dengue, chikungunya, and Zika. The number represents 37.4% of the municipalities surveyed by the ministry in the Quick Survey of Rates for Aedes aegypti (LIRa, in the original acronym), the mosquito that transmits these illnesses.

Among the 22 state capitals covered by the study, Cuiabá, in Mato Grosso state, was reported as facing a risk situation and nine others are said to be on alert, and 12 were described as satisfactory—among which São Paulo, Rio de Janeiro, and Brasília.

Water barrels, drums, and tanks were the main breeding sites mentioned for the Northeast and the South. Predominant in the Southeast, however, was household, a category which includes plant vases, bottles, swimming pools, and gutters. In the North and the Central West, most sites were to be found in trash.

Reduction in dengue cases

The data show a 5.5% decline in the cases of dengue fever. Altogether, 1,458,355 cases were reported by 22 October this year, and 1,543,000 by the same date in 2015.

The highest incidence of the illness was observed in the Southeast and the Northeast, with 848,587 and 322,067 respectively, followed by the Central West (177,644), the South (72,114), and the North (37,943).

The study also registered 601 deaths stemming from the disease this year, compared to 933 in the same period last year—a reduction of 35.6%. The cases of severe dengue also underwent a major fall, from 1,616 to 803, whereas dengue with warning signs shrank from 20,352 to 7,730.

Chikungunya on the rise

The survey reports 251,051 suspected cases of chikungunya fever identified in the country this year, 135,910 of them confirmed. In the same period last year, suspected and confirmed cases added up to 26,763 and 8,528 respectively. Deaths from the disease totaled 138 throughout the country.

Thus far, 2,281 of the 5,570 Brazilian municipalities have reported infection with the chikungunya virus.

Incidence of Zika

Concerning the Zika virus, 208,867 suspected cases were reported in the country until October 22. This number represents an incidence rate of 102.2 cases per 100,000 inhabitants. Three deaths caused by the disease were also confirmed this year, in addition to 16,696 suspected cases of infection among pregnant women.

The autochthonous transmission of Zika virus in Brazil was confirmed in April 2015. Only in February 2016, it became mandatory to report cases of Zika infection to the Ministry of Health. Thus, there are no previous data to make comparisons.

Respondents

A total of 2,284 cities of the 3,704 cities that would be able to respond to the Quick Survey of Rates for Aedes aegypti (LIRAa in the original acronym) have responded to this year's edition—equivalent to 62.6% of the total.

Conducted between October and November, the study is considered an essential tool for the mosquito control. Based on information collected, the health agent can identify the most common type of breeding site and propose measures that give priority to preventing the virus vector from spreading the infection in the municipality.

Currently, participants voluntarily  respond to the survey, but the government expects to make the participation mandatory for cities with over 2,000 properties.

Translated by Amarílis Anchieta / Fabrício Ferreira