简体中文
Zika virus infection in pregnancy is "the most likely explanation" behind congenital brain abnormalities in babies including microcephaly, the World Health Organization says.Another study ofWashington University School of Medicine in St. Louis, published Sept. 6 in Cell Reports, also describes the effect of Zika virus infection in the eyes of mouse fetuses, newborns and adults.
"Based on observational, cohort and case-control studies there is strong scientific consensus that Zika virus is a cause of GBS, microcephaly and other neurological disorders," the agency said in a statement on Wednesday. The Zika virus is spread by mosquitoes and can also be sexually transmitted.
Across Brazil hundreds of infants have been born with microcephaly. The World Health Organization has now declared the Zika virus a "public health emergency of international concern" Photo: independent.co.uk
In February, WHO declared that the clusters of cases of microcephaly and neurological disorders occurring in areas with Zika virus transmission an international public health emergency. Last week, it said the outbreak remains an international health emergency and the virus is continuing to infect new countries, such as in Southeast Asia.
Zika infections in pregnant women have been shown to cause microcephaly — a severe birth defect in which the head and brain are undersized — as well as other brain abnormalities.
Zika virus causes mild disease in most adults but can cause brain damage and death in fetuses. About a third of all babies infected in utero with Zika show eye disease such as inflammation of the optic nerve, retinal damage or blindness after birth. In adults, Zika can cause conjunctivitis -- redness and itchiness of the eyes -- and, in rare cases, uveitis.
The study, in mice, helps explain why some Zika patients develop eye disease including a condition known as uveitis which can lead to permanent vision loss.
Researchers have found that Zika virus can live in eyes and have identified genetic material from the virus in tears.The researchers now are planning complementary studies in human patients infected with the virus.
Eye infection raises the possibility that people could acquire Zika infection through contact with tears from infected people. The researchers found that the tears of infected mice contained Zika's RNA -- the genetic material from the virus -- but not infectious virus when tested 28 days after infection.
Zika researchers are increasingly considering alternative routes of transmission because the virus is spreading more quickly than would be expected by mosquito-borne transmission alone. Epidemiologists can predict the spread of a disease based on known rates of transmission for related viruses and the viral level in the bloodstreams of infected people. By those calculations, Zika is moving unusually fast.
The connection between Zika and microcephaly first came to light last fall in Brazil, which has since confirmed more than 1,800 cases of microcephaly.
Travellers are advised to protect themselves from mosquito bites at all times. The vast majority of people infected with Zika have a mild infection and about 80 per cent have no symptoms. The symptoms include mild fever, rash and red eyes.
(APD)
