BOSTON >> There have been 10 confirmed cases of Zika virus in Massachusetts, but the mosquito-borne virus is not expected to spread here, state public health officials said.
"Based on all available evidence, we consider it extremely unlikely we will see local mosquito-borne transmission of Zika in Massachusetts," Dr. Catherine Brown, the deputy state epidemiologist at the Department of Public Health, told the News Service. "But that doesn't mean there is nothing for us to do in response."
Zika is a mosquito-spread virus that can cause fever, rash, joint pain, and conjunctivitis, according to DPH. About 80 percent of people who become infected do not show symptoms, but symptoms generally last up to one week and then go away without additional problems.
DPH has been working with the federal Centers for Disease Control and health care providers to identify any pregnant women who have traveled to areas where Zika has been transmitted, like South or Central America, in order to test them for Zika exposure, Brown said.
Zika infections in pregnant women in South America and Asia have been linked to cases of microcephaly — a fetal malformation that affects the size of a baby's brain and head — and Brown said pregnant women exposed to Zika could risk losing their fetus.
"Because of the particular risk of Zika virus to pregnant women, we're making the very strong recommendation that if you are pregnant or planning on becoming pregnant in very near future that you should avoid traveling to places where Zika virus transmission is ongoing," Brown said. "At this time the risk to pregnant women just isn't worth it."
Feeding into DPH's confidence that Zika will not spread in Massachusetts is the fact that the type of mosquito primarily responsible for transmitting the virus "has never been found in Massachusetts," Brown said.
But one other type of mosquito that can transmit the virus has been found in the state, she said, though it is not all that common.
"There have been kind of isolated findings in Massachusetts of that mosquito, but we do not have widespread, established populations of that mosquito," Brown said. "And that's one of the reasons we really consider it extremely unlikely we will see any mosquito-borne spread of Zika here."
That mosquito — Aedes albopictus — is native to Asia and first spread to the United States via a shipment of used tires from Asia that was offloaded in Houston in the mid-1980s, according to the CDC. As that species moved north, Massachusetts began to monitor its population here and has stepped up that monitoring in recent years.
"That surveillance started back in 2008 because of the recognition that this was a mosquito introduced in the southern tier of the United States gradually working its way northwards," Brown said. "We didn't want to wait until it was too late and be surprised by its arrival. That monitoring was quite enhanced in 2013-14 and we're going to continue that enhanced monitoring."
Online: DPH Presentation on Zika Virus