A relatively new mosquito-borne virus is prompting worldwide concern because of an alarming connection to a neurological birth disorder and the rapid spread of the virus across the globe.
The Zika virus is a flavivirus, part of the same family as yellow fever, West Nile, chikungunya and dengue. But unlike some of those viruses, there is no vaccine to prevent Zika or medicine to treat the infection.
Flaviviruses are named from the yellow fever virus, the type virus for the family; the word flavus means “yellow” in Latin. The name yellow fever originated from its propensity to cause yellow jaundice in victims.)
Zika is commanding worldwide attention because of an alarming connection between the virus and microcephaly, a neurological disorder that results in babies being born with abnormally small heads. This causes severe developmental issues and sometimes death.
ZIKA virus was first isolated in 1947, in a rhesus monkey at Uganda’s Zika Forest.
The World Health Organisation says the symptoms are usually mild and normally last two to seven days. Symptoms are similar to dengue and chikungunya and include:
- a mild fever,
- skin rash,
- aches and pains,
- headache, and
About one in five people infected with the virus become ill. Zika virus usually remains in the blood of an infected person for about a week.
Zika is spread by mosquitoes of the Aedes species, which can breed in a pool of water as small as a bottle cap and usually bite during the day. The aggressive yellow fever mosquito, Aedes aegypti, has spread most Zika cases,The Asian tiger mosquito, Aedes albopictus, is also known to transmit the virus, but it is not clear how efficiently.
Although the virus is normally spread by mosquitoes, there has been one report of possible spread through blood transfusion and one of possible spread through sex. The virus was found on one occasion in semen.
Babies with microcephaly have unusually small heads. In roughly 15 percent of cases, a small head is just a small head, and there is no effect on the infant, according to Dr. Constantine Stratakis, a pediatric geneticist and a scientific director at the National Institute of Child Health and Human Development.
But in the remainder of cases, the infant’s brain may not have developed properly during pregnancy or may have stopped growing in the first years of life. These children may experience a range of problems, like developmental delays, intellectual deficits or hearing loss.
The consequences can vary widely from child to child. Pinpointing an underlying cause helps clinicians to advise parents about their newborn’s prognosis.
Genetic abnormalities are a common cause. Microcephaly can also be triggered by infections of the fetus, including German measles (also known as rubella), toxoplasmosis (a disease caused by a parasite, often in cat feces) and cytomegalovirus.
Microcephaly may also result if a pregnant woman consumes alcohol, is severely malnourished or has diabetes. If the defect occurs in a child’s first years, it may be a result of a brain injury during labor.
There is no treatment for an unusually small head.
“There is no way to fix the problem, just therapies to deal with the downstream consequences,” said Dr. Hannah M. Tully, a neurologist at Seattle Children’s Hospital who specializes in brain malformations.