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

Researchers in contrast information for pregnant girls in Rio de Janeiro and Manaus who have been contaminated by zika virus in 2015-16. Elements that influenced the chance of fetal malformation have been the excessive zika assault fee within the space and being contaminated within the first trimester of being pregnant. Credit score: TV Brasil

A pregnant lady contaminated by Zika virus doesn’t face a larger danger of giving delivery to a child with microcephaly if she has beforehand been uncovered to dengue virus, based on a Brazilian examine that in contrast information for pregnant girls in Rio de Janeiro and Manaus.

A Zika epidemic broke out in Brazil in 2015-16 in areas the place dengue is endemic. Each viruses are transmitted by the mosquito Aedes aegypti. Among the states affected by the Zika epidemic reported an increase in circumstances of microcephaly, a uncommon neurological dysfunction wherein the infant’s mind fails to develop utterly. Others noticed no such rise.

Based on this new examine by Brazilian researchers, two components clarify the rise in microcephaly in just some areas: The excessive Zika assault fee, and the mom’s having contracted the virus within the first trimester of being pregnant. The time period assault fee in epidemiology refers back to the variety of circumstances divided by the entire inhabitants.

The examine was supported by FAPESP by way of two tasks (16/15021-1 and 13/21719-3), and was performed beneath the aegis of the Community for Analysis on Zika Virus in São Paulo (Rede Zika). The outcomes are described in an article in Viruses, a peer-reviewed open-access journal printed by the Multidisciplinary Digital Publishing Institute (MDPI). The article appeared in late April in a particular problem on Zika and being pregnant.

“The discrepancies between areas by way of the numbers of reported circumstances of microcephaly through the Zika epidemic have been puzzling. One of many hypotheses was that prior publicity to dengue may make Zika extra extreme, however within the state of São Paulo there weren’t many adversarial results of Zika despite the fact that the area is very endemic for dengue, so we determined to attempt to discover out what might clarify the variations,” stated virologist Maurício Lacerda Nogueira, a professor on the São José do Rio Preto Medical College (FAMERP) in São Paulo, and co-principal investigator for the examine alongside Patrícia Brasil, a researcher at Oswaldo Cruz Basis (FIOCRUZ) in Rio de Janeiro.

Based on Nogueira, their consideration was drawn to the assault fee once they analyzed the info for the 2 state capitals. In Rio de Janeiro, the place many circumstances of microcephaly have been reported, the variety of folks contaminated by Zika virus corresponded to 10 per 10,000 inhabitants, whereas in Manaus, the place comparatively few infants have been born with microcephaly, the assault fee was 0.6 per 10,000.

“Microcephaly attributable to Zika is a uncommon phenomenon, however when there are lots of circumstances of Zika in an space it turns into extra obvious. It had been recommended earlier that contracting Zika within the first trimester of being pregnant is perhaps related, and now we have proved that it was,” Nogueira stated.


The researchers got down to perceive the variations within the adversarial outcomes of being pregnant and within the infants of the 2 populations by finding out 114 pregnant girls contaminated by Zika virus between September 2015 and June 2016. An infection was confirmed by RT-qPCR testing of blood and/or urine samples. The themes have been recruited at Heitor Vieira Dourado Tropical Medication Basis (FMT-HVD), an infectious illness hospital in Manaus, and FIOCRUZ’s acute febrile sickness clinic in Rio de Janeiro.

Prior publicity to dengue was assessed by serological assessments to detect neutralizing antibodies, amongst others. The purpose was to discover potential associations between being pregnant outcomes and the Zika assault fee, outlined because the variety of circumstances formally reported through the examine interval divided by the inhabitants of every metropolis.

Total, 31 girls had adversarial outcomes (27 in Rio and four in Manaus). On this group, 4 infants died earlier than delivery and 27 have been born with mind anomalies. “Solely Zika assault charges and an infection within the first trimester of being pregnant have been related to adversarial being pregnant and toddler outcomes. Pre-existing immunity to dengue was not related to outcomes (regular or irregular) in sufferers with Zika throughout being pregnant,” the authors of the article state within the Summary.

And so they conclude, “The strengths of our examine embody a cautious classification of toddler outcomes, made potential via detailed assessments at delivery by a multidisciplinary group. […] As well as, using a extremely delicate and particular [plaque reduction neutralizing antibody] assay to characterize pre-existing dengue immunity and using sera collected through the acute section of RT-PCR-confirmed Zika an infection lend credibility to our outcomes. […] Our major limitations are the modest pattern measurement and comfort pattern choice.”

An earlier examine led by Nogueira in 2017 confirmed that sufferers contaminated by Zika after publicity to dengue didn’t grow to be extra severely in poor health than different folks. It was the primary scientific examine to indicate this in people. Prior analysis involving cells and rodents had recommended the other.


Microcephaly is a uncommon neurological situation wherein an toddler’s head and mind are considerably smaller than regular because of alterations within the formation of the nervous system throughout improvement within the womb. Kids with microcephaly often undergo from retarded or blocked psychological, bodily and motor improvement.

The causes of microcephaly embody genetic components and publicity to chemical compounds, micro organism and viruses. Scientists have just lately proven that Zika contracted throughout being pregnant can impair fetal improvement.

Throughout the epidemic in Brazil, Zika affected folks of all ages and was related to the incidence of numerous circumstances of microcephaly. In November 2015, Brazil declared a public well being emergency due to the rising variety of circumstances. The World Well being Group (WHO) then issued an epidemiological alert, stressing the potential of congenital neurological malformations in infants born to girls contaminated by Zika.

In 2015 alone, greater than 2,400 circumstances of microcephaly have been reported in Brazil. They occurred in about 540 municipalities in 20 states. Within the interval 2010-14, the entire variety of reported circumstances was 781.

In 2016 there have been some 214,000 possible circumstances of Zika. The quantity fell to 17,000 in 2017 and eight,000 in 2018. Within the first three months of this yr, it was 448, based on the Ministry of Well being’s epidemiological bulletin.

The signs of Zika are just like these of dengue. In most contaminated folks, it causes fever, headache, pink eyes, joint ache and rash. On common, the signs disappear in ten days.

The researchers are continuing with their evaluation of the interactions between Zika and dengue, notably to see if Zika modulates an infection by dengue virus. Nogueira additionally participates in a global group that’s engaged on fashions to foretell epidemics of Zika, dengue and yellow fever.


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