A study of 3,000 children during an outbreak in Nicaragua showed that those previously infected with dengue were less likely to develop Zika symptoms. Both Zika and Dengue viruses are, transmitted by the same type of mosquitoes and cause similar symptoms.
The dengue virus has been present in the Americas for decades, while Zika did not appear in Brazil until 2015, before spreading rapidly. The dengue and Zika viruses are transmitted by the bite of the Aedes aegypti mosquito and cause similar symptoms to the flu: fever, muscle, and joint pain, etc. There may also be redness in the skin.
However, in pregnant women, a Zika infection can lead to serious disturbances in the development of the fetus, especially microcephaly. Neurological complications (Guillain-Barré syndrome) are also possible in infected women. However, Zika infection is often asymptomatic.
When someone becomes infected with dengue for the second time, it often happens that the second infection is more severe than the first. Since Zika viruses and dengue are similar, it is questionable whether a Zika infection following a dengue infection would be more serious.
Cross Immunity between two closely related viruses
In a study published in PLOS Medicine, the authors analyzed an epidemic of Zika in Managua, Nicaragua. They examined over 3,000 children from 2 to 14 years of age, many of whom had previously been infected with dengue fever. Using blood samples, the researchers were able to detect a Zika infection even without symptoms.
Between January 2016 and February 2017 there were 1,356 Zika infections in this cohort of children, 560 of which led to symptoms. The researchers had the medical history of 3,027 children, 743 of whom were infected with dengue fever at least once. The results show that children infected with dengue before March 2015 had a significantly lower risk of developing Zika symptoms (about 40% less risk).
Therefore, being previously infected with dengue does not lead to a worsening of Zika’s symptoms, as the opposite seems to be the case. Therefore, there would be some kind of mutual protection between these two viruses, even if an infection with the dengue virus would not prevent a Zika infection. Dengue could thus protect against Zika’s neurological complications.
This work was carried out by research institutes in the United States and Nicaragua.