The new lab study shows that previous exposure to DENV can drive greater ZIKV replication, and potently enhance ZIKV infection. The study was published in the journal Nature Immunology.
Zika virus is an enveloped virus that is transmitted to man by Aedes mosquitos. It belongs to the Flavivirus genus in the family Flaviviridae, which also includes the human pathogenic dengue viruses. DENV exists as four serotypes, and dengue infections are caused by four closely related viruses named DEN-1, DEN-2, DEN-3, and DEN-4.
Most ZIKV infections are asymptomatic, and symptomatic cases of ZIKV resemble mild cases of dengue fever, with symptoms of fever, muscle pain, joint pain, headache, conjunctivitis and rash.
Zika virus infection can cause strong neurological complications such as Guillain Barré syndrome, which was first reported following the outbreak in French Polynesia in 2013. Dramatic spikes in the incidence of microcephaly in Brazil were reported in 2015, coincident with a large increase in zika virus infection.
Aedes aegypti is believed to be the principal species responsible for the current outbreaks. In parts of Brazil, A. aegypti is also spreading dengue virus concurrently with ZIKV. DENV has spread through areas of South America, and the seroprevalence of DENV in some areas affected by ZIKV exceeds 90%.
Three-dimensional cryo-electron microscopy structures of the mature ZIKV particles show that the virus has essentially the same organization as dengue virus.
There is difficulty in distinguishing DENV infection versus ZIKV infection serologically, and this shows a degree of antigenic similarity between the viruses.
These features help to explain why the two viruses have extensive serological cross-reaction between each other. The zika virus differs from the dengue virus by around 41–46% (in the sequence of the envelope protein). But the similarities are enough to cause cross-reaction of antibodies to DENV with ZIKV and to drive antibody-dependent enhancement of ZIKV infection.
This study has implications for the design of a zika vaccine, and of a dengue vaccine. There could be a possibility of developing a universal vaccine protecting against all the viruses from the Flavivirus group.
There is an even more urgent need to develop safe and effective vaccines against these 2 viruses, and to intensify efforts to prevent infection from the dengue virus by other mean such as mosquito eradication, and the use of mosquito repellants. And of course, such efforts will also help to prevent zika infection.
How to protect yourself against zika and dengue
Based on this new study, if you have previously had dengue fever, it’s very important to avoid countries and areas with zika outbreaks. If you go to these areas, you might be infected with the zika virus, and your infection could be worse than the usual cases.
Even if you never had dengue fever, you must use measures that protect you from mosquitoes that carry zika and dengue viruses.
The CDC recommends you use products with these ingredients:
If you travel to outbreak areas, wear long-sleeved shirts, long pants, boots, and hats. Tuck in shirts, tuck pants into socks, and wear closed shoes.
Use bed nets treated with a pyrethroid insecticide. If nets don’t reach the floor, they should be tucked under mattresses.
The CDC states
- “Do not use insect repellent on babies younger than 2 months old.
- Do not apply insect repellent onto a child’s hands, eyes, mouth, and cut or irritated skin.
- Adults: Spray insect repellent onto your hands and then apply to a child’s face.
- Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under 3 years old.
- Cover crib, stroller, and baby carrier with mosquito netting.’’
Please note that zika can be passed through sex from a person who has zika to his or her sex partners.
Until we have effective vaccines, take the above measures to protect yourself from the zika and dengue viruses.