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A study conducted in Salvador shows that the fear of a dangerous interaction between dengue and Zika viruses in the body of infected people is probably unfounded, reveals a zika epidemic in 2015.
Blood samples taken from nearly 1,500 inhabitants of the Pau da Lima district in the Brazilian capital, Brazilian and American scientists concluded that the heavy circulation of the dengue virus before the arrival of zika in the region not aggravate the impact of the new disease. 19659002] In fact, the reverse seems to have happened: people who carried a lot of antibodies (molecules of defense of the organism) against dengue were more likely to d & # 39; avoid the new disease. That is, in practice, dengue has been protected several times previously against zika. The results are described in an article that just appeared in the journal Science.
"Such epidemiological studies are expensive and take time to bear fruit, and it was more or less clear that we would not understand better than what was happening in the case of zika when the epidemic was getting weaker. suggests that the disease is now present in Brazil, so it is important to understand it, "he told the virolologist Folha Mauricio Lacerda Nogueira, co-author of the research and professor at the Faculty of Medicine from São José do Rio Preto. Federico Costa, of Fiocruz (Oswaldo Cruz Foundation) of Bahia, and Albert Ko of the School of Public Health, Yale University, USA
Specialists use the acronym ADE (antibody-dependent potentiation) for describe the phenomenon that could define an infection aggravated by another previous infection
The ADE process seems to be at the origin of the risk that exists when a person is affected by two different forms of the dengue virus, for example. In the second infection, the possibility of severe symptoms leading to death increases (19659002). In these cases, it appears that antibodies produced by the body during the first infection can connect to the new virus, but can not neutralize it.
Since the zika virus is a close relative of the cause of dengue (both belonging to the flavivirus group), it is possible that it happened to exist. And the data to directly badyze the phenomenon were also available because Albert Ko and his colleagues were conducting a long-term public health research project in Salvador (Yale's doctor had resided in Brazil since then). 15 years old) [19659002] Thanks to this, the team badyzed both the presence of antibodies against the zika virus, indicative of infection by the pathogen, and the antibodies directed against dengue (in a sub- smaller group of inhabitants of Pau da Lima, totaling 642 people).
The first major conclusion of the survey is that the new virus would have spread with extraordinary force by 2015. According to the population, about 70% of the inhabitants of the region had zika during this period (This is an estimate and not a certainty, since antibody badysis has a certain margin of error.)
Of the 642 subgroup, 86% had at least some antibodies against dengue fever. This was not enough to make these people immune to zygaxis; the higher the amount of anti-dengue antibodies in their body, the less likely they were to be infected with zika.
divided into three parts depending on the level of antibodies in the body, one-third of people with more dengue antibodies were 44% less likely to contract zika than a third of those with less antibody or having no defense against dengue
According to Ko, the result is good news for current and future trials on the dengue vaccine. The role of vaccines being precisely to stimulate the action of the body's defense system and the production of antibodies, there was a fear that they could cause the effect not intentional of the potentiation of zika. "This would be the worst case considering conbad anomalies, such as microcephaly, that the disease can cause during pregnancy," he says.
And the data could help quantify why thousands of microcephaly appeared in the country, and particularly in the northeast, after the peak of the epidemic, with a return to the expected level of the problem. "The incredibly high rate of infection in communities such as our study was certainly the main reason," says Ko.
"If the proportion of 70% of the population is even representative, imagine what this represents for the Northeast: as a whole, "added Mauricio Nogueira. There would be 40 million people. "With so many cases, the relatively rare effects of infection are beginning to be visible."
After the first infection, it seems that the person becomes immune to new attacks of the zika virus, which would prevent the phenomenon from repeating itself with the same intensity in the years to come. However, over time, after the birth of people whose body has not been in contact with the pathogen, a reservoir of possible victims is created. This is why it is important to prepare for future attacks.
Antibodies against one of the parasites may protect against the other
- The dengue virus and the Zika virus are part of the flavivirus group, which also includes the cause of yellow fever. The relationship between the first two parasites is particularly close
- Since dengue fever is an endemic disease in many Brazilian populations, it was feared that the infection of people already affected by the Zika virus would potentiate the effects of the new disease. This is what happens sometimes in those who already had a dengue subtype and whose body was attacked by another subtype of the same virus.
- Analysis of blood samples taken from nearly 1,500 inhabitants of a community of Salvador, collected during the zika epidemic. of 2015 showed that this probably did not happen: the risk that individuals with high titers of dengue antibodies also taking zika would be 44% lower than those with low prevalence. 39, antibody against dengue or never having suffered from the disease
- This is good news for future dengue vaccine trials: in theory, the risk that immunization against the disease potentiates the effects of zika is weak
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