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Study refutes suspicion that dengue will increase threat of microcephaly related to Zika

Publicado em 20 julho 2021

A pregnant girl contaminated by Zika virus doesn’t face a larger threat of giving start to a child with microcephaly if she has beforehand been uncovered to dengue virus, in line with a Brazilian examine that in contrast information for pregnant ladies in Rio de Janeiro and Manaus.

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

According to this new examine by Brazilian researchers, two elements 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 instances divided by the whole inhabitants.

The examine was supported by FAPESP through two initiatives (16/15021-1 and 13/21719-3), and was performed beneath the aegis of the Network for Research 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 difficulty on Zika and being pregnant.

“The discrepancies between regions in terms of the numbers of reported cases of microcephaly during the Zika epidemic were puzzling. One of the hypotheses was that prior exposure to dengue might make Zika more severe, but in the state of São Paulo there weren’t many adverse effects of Zika even though the region is highly endemic for dengue, so we decided to try to find out what could explain the differences,” mentioned virologist Maurício Lacerda Nogueira, a professor on the São José do Rio Preto Medical School (FAMERP) in São Paulo, and co-principal investigator for the examine alongside Patrícia Brasil, a researcher at Oswaldo Cruz Foundation (FIOCRUZ) in Rio de Janeiro.

According to 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 instances of microcephaly have been reported, the variety of individuals 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 caused by Zika is a rare phenomenon, but when there are many cases of Zika in an area it becomes more apparent. It had been suggested earlier that contracting Zika in the first trimester of pregnancy might be relevant, and now we’ve proved that it was,” Nogueira mentioned.


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 ladies contaminated by Zika virus between September 2015 and June 2016. Infection was confirmed by RT-qPCR testing of blood and/or urine samples. The topics have been recruited at Heitor Vieira Dourado Tropical Medicine Foundation (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 objective was to discover potential associations between being pregnant outcomes and the Zika assault fee, outlined because the variety of instances formally reported through the examine interval divided by the inhabitants of every metropolis.

Overall, 31 ladies had adversarial outcomes (27 in Rio and 4 in Manaus). In this group, 4 infants died earlier than start and 27 have been born with mind anomalies. “Only Zika attack rates and infection in the first trimester of pregnancy were associated with adverse pregnancy and infant outcomes. Pre-existing immunity to dengue was not associated with outcomes (normal or abnormal) in patients with Zika during pregnancy,” the authors of the article state within the Abstract.

And they conclude, “The strengths of our study include a careful classification of infant outcomes, made possible through detailed assessments at birth by a multidisciplinary team. […] In addition, the use of a highly sensitive and specific [plaque reduction neutralizing antibody] assay to characterize pre-existing dengue immunity and the use of sera collected during the acute phase of RT-PCR-confirmed Zika infection lend credibility to our results. […] Our main limitations are the modest sample size and convenience sample selection.”

An earlier examine led by Nogueira in 2017 confirmed that sufferers contaminated by Zika after publicity to dengue didn’t turn out to be extra severely in poor health than different individuals. It was the primary scientific examine to indicate this in people. Prior research involving cells and rodents had prompt 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 growth within the womb. Children with microcephaly often endure from retarded or blocked psychological, bodily and motor growth.

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

During the epidemic in Brazil, Zika affected individuals of all ages and was related to the prevalence of numerous instances of microcephaly. In November 2015, Brazil declared a public well being emergency due to the rising variety of instances. The World Health Organization (WHO) then issued an epidemiological alert, stressing the opportunity of congenital neurological malformations in infants born to ladies contaminated by Zika.

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

In 2016 there have been some 214,000 possible instances of Zika. The quantity fell to 17,000 in 2017 and eight,000 in 2018. In the primary three months of this 12 months, it was 448, in line with the Ministry of Health’s epidemiological bulletin.

The signs of Zika are just like these of dengue. In most contaminated individuals, it causes fever, headache, crimson 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, significantly 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.

Dengue virus infection may cause severe outcomes following Zika virus infection during pregnancy

More data:
L. Damasceno et al. Why Did ZIKV Perinatal Outcomes Differ in Distinct Regions of Brazil? An Exploratory Study of Two Cohorts, Viruses (2021). DOI: 10.3390/v13050736

Study refutes suspicion that dengue will increase threat of microcephaly related to Zika (2021, July 20)
retrieved 20 July 2021

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