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Study refutes suspicion that dengue increases risk of microcephaly associated with Zika

Publicado em 20 julho 2021

A Brazilian study comparing data from pregnant women in Rio de Janeiro and Manaus shows that pregnant women infected with Zika virus are not at increased risk of giving birth to a baby with microcephaly if they have previously been infected with dengue virus. ..

The Zika epidemic occurred in Brazil in 2015-16. Dengue fever I have endemic disease. Both viruses are transmitted by Aedes aegypti. Some of the states affected by the Zika epidemic Microcephaly, A rare neuropathy in which the baby’s brain does not fully develop. Others did not see such a rise.

According to this new study by Brazilian researchers, two factors explain the increase in microcephaly only in some areas. The high incidence of Zika virus and the mother’s infection with the virus during the first semester of pregnancy. The term epidemiological incidence refers to the number of cases divided by the total population.

This study was supported by FAPESP through two projects (16/15021-1 and 13/21719-3) and was carried out with the support of the Zika virus research network in São Paulo (Rede Zika).The results are described in the article Virus, A peer-reviewed open access journal published by the Multidisciplinary Digital Publishing Institute (MDPI). This article was published in a special issue on Zika fever and pregnancy in late April.

“Regional disagreements regarding the number of cases of microcephaly reported during the Zika epidemic were puzzling. One hypothesis is that previous exposure to Zika could make Zika more severe. It was said to be sexual, but not so much in the state of São Paulo. Despite the fact that the area is very prevalent in Zika, the negative effects of Zika can explain the difference. I decided to find it, “said Mauricio La Serda Nogueira, a virologist at the University of São Paulo Sedrio Preto Medical School (FAMERP). Co-principal researcher for research with Sao Paulo and Patricia Brazil, a researcher at the Oswaldo Cruz Foundation (FIOCRUZ) in Rio de Janeiro.

According to Nogueira, when analyzing data from the two state capitals, their attention was directed to attack rates. In Rio de Janeiro, where there are many cases of microcephaly, the number of people infected with Zika virus is equivalent to 10 per 10,000 inhabitants, and in Manaus, where there are relatively few babies born with microcephaly, the incidence rate is 0.6 per 10,000 people. It was a person.

“Microcephaly due to Zika fever is a rare phenomenon, but it becomes clear that there are many cases of Zika fever in some areas. Previously, it may be related to infection with Zika virus in the early stages of pregnancy. It was suggested by, but now it seems to be proven. “


Researchers attempted to understand the harmful consequences of pregnancy and the differences between the two populations of babies by investigating 114 pregnant women infected with the dicavirus between September 2015 and June 2016. I did. Infection was confirmed by blood RT-qPCR test. Or a urine sample. Subjects were recruited at the Heitor Vieira Dourado Tropical Medicine Foundation (FMT-HVD), a hospital for infectious diseases in Manaus, and at the FIOCRUZ Acute Fever Disease Clinic in Rio de Janeiro.

Previous exposure to dengue fever was assessed, among other things, by serological tests to detect neutralizing antibodies. The goal was to investigate the potential association between pregnancy outcomes and the incidence of Zika fever. This is defined as the number of cases officially reported during the study period divided by the population of each city.

Overall, 31 women had unfavorable results (27 in Rio and 4 in Manaus). In this group, four babies died before birth and 27 were born with brain abnormalities. “Only the incidence and infection of Zika in early pregnancy were associated with adverse outcomes of pregnancy and infants. Outcomes (normal or abnormal) of pregnant Zika patients were associated with existing immunity to dengue. I didn’t, “the authors said. The state of the abstract article.

And they said, “The strengths of our research include a careful classification of infant outcomes made possible through detailed birth assessments by interdisciplinary teams. […] In addition, very sensitive and specific use [plaque reduction neutralizing antibody] The assays that characterize existing dengue immunity and the use of serum collected during the acute phase of Zika infection confirmed by RT-PCR provide confidence in our results. […] Our main limitations are modest sample size and convenient sample selection. “

An early study led by Nogueira in 2017 showed that patients infected with Zika after being exposed to dengue were less severe than others. It was the first scientific study to show this to humans. Previous studies involving cells and rodents He was proposing the opposite.


Microcephaly is a rare neurological condition in which the baby’s head and brain become significantly smaller than normal as a result of changes in the formation of the developing nervous system in the womb. Children with microcephaly usually suffer from delayed or blocked mental, physical and motor development.

Causes of microcephaly include exposure to genetic factors, chemicals, bacteria, and viruses. Scientists have recently shown that Zika fever that develops during pregnancy can impair fetal development.

During the Brazilian epidemic, Zika fever affected people of all ages and was associated with the occurrence of numerous cases of microcephaly. In November 2015, Brazil declared a public health emergency due to an increase in the number of cases. The World Health Organization (WHO) then issued an epidemiological warning, highlighting the possibility of congenital neurological malformations in babies born to women infected with Zika virus.

In 2015 alone, more than 2,400 cases of microcephaly were reported in Brazil. They occurred in about 540 municipalities in 20 states. The total number of cases reported during the 2010-14 period was 781.

In 2016, there were about 214,000 possible cases of Zika fever. According to the Ministry of Health’s epidemiological bulletin, the number decreased to 17,000 in 2017 and 8,000 in 2018. There were 448 people in the first three months of this year.

The symptoms of Zika fever are similar to those of dengue fever. Most infected people cause fever, headaches, red eyes, joint pain, and rashes. On average, the symptoms disappear in 10 days.

Researchers are proceeding with an analysis of the interaction between Zika and dengue, especially to see if Zika regulates infection. Dengue virus.. Nogueira also participates in an international group working on models to predict epidemics of Zika, dengue and yellow fever.

Dengue virus infection can have serious consequences after Zika virus infection during pregnancy

For more information:

L. Damasceno et al. Why do different regions of Brazil have different ZIKV perinatal outcomes? Exploratory study of two cohorts, Virus (2021). DOI: 10.3390 / v13050736

Quote: The study refutes the suspicion that dengue fever increases the risk of microcephaly associated with Zika (July 20, 2021).

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