Two babies in California have been born with the severe birth defect microcephaly after their mothers were infected with the Zika virus while traveling in foreign countries where the virus is common, state public health officials announced Thursday.
Because of privacy concerns, state officials would not release any more information about who the mothers are, where they live and where they traveled, other than to say the cases occurred this year. They are the first reported cases of babies born with microcephaly in the state in connection with the Zika virus.
As of July 28, 15 babies had been born in the U.S. with Zika-related birth defects, according to the Centers for Disease Control and Prevention. It’s not clear whether the California babies are included in the CDC tally.
Another six babies with Zika-related birth defects in the U.S. were miscarried or stillbirths, according to the CDC.
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One of the California mothers has returned with her affected infant to her home country, said Dr. Karen Smith, director of the state Department of Public Health. State officials would not identify that country but said Zika is actively transmitted there.
The two primary mosquito species capable of transmitting Zika – Aedes aegypti and Aedes albopictus – are found in 12 California counties, but they have not been detected in Sacramento County, according to the Sacramento-Yolo Mosquito and Vector Control District. The mosquitoes have been found as far north as Hayward and Menlo Park in the Bay Area and in Central Valley cities such as Madera, Fresno and Clovis.
The virus can also be spread through sexual contact.
“We have recognized since the beginning of the Zika event that we could see limited local transmission within California but we do believe that would be a very limited local transmission,” Smith said.
Babies with microcephaly are born with abnormally small heads and suffer neurological defects. In severe cases, people with microcephaly may experience seizures, learning disabilities and a shortened lifespan. In mild cases, a person might live a full life but experience hearing loss or have trouble swallowing.
The condition occurs when exposure to a chemical or virus impairs an infant’s brain development, usually within a mother’s first trimester of pregnancy, according to the National Institutes of Health. Alcohol, malnutrition and the virus rubella are associated with microcephaly, according to the CDC.
About 25,000 infants are born every year in the U.S. with microcephaly, according to a 2009 study by researchers at Loma Linda University School of Medicine.
Between 1 and 13 percent of women who became infected with Zika in the first three months of pregnancy will give birth to a baby with microcephaly, according to the CDC.
“It’s a big range, and that’s a problem because that’s what people want to know,” said Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children’s Hospital.
Local doctors have been fielding questions about microcephaly risk for much of this year, since a Zika outbreak was reported in Brazil and then much of Latin America and the U.S. territory of Puerto Rico.
The state has reported 114 cases of travel-associated Zika infections as of July 29 in 22 California counties. Last week, Sacramento County reported its first case of Zika virus, also transmitted during travel.
There have been no reports of locally transmitted Zika virus in California.
The California Department of Public Health this week received a $720,000 grant from the CDC to identify and treat babies born with microcephaly. Smith said the state will be monitoring the two women and their infants for a year. Before Thursday’s announcement, the state had already been following the cases of 21 pregnant women confirmed to have Zika, including those of the two women who gave birth to microcephalic babies.
In the 50 U.S. states, 1,657 cases of Zika infections have been reported as of July 27, the CDC reports. Four locally transmitted cases have been confirmed in Florida.
Another 4,729 cases of locally transmitted Zika and 21 cases of travel-associated Zika have been reported in U.S. territories, according to the CDC. There have been no babies born with a Zika-related birth defect in any U.S. territory.