By Jeanne Kim,
Zika virus, a mosquito-borne pathogen transmitted by Aedes aegypti and Aedes albopictus mosquitoes, has had prominent and devastating effects in the past several months, primarily in Latin American countries.
In the early weeks of February, a Zika case was reported in Yolo County. The person who tested positive was said to have contracted the virus while out of the country, and could have transmitted the virus if bitten by an Aedes mosquito in a country with said mosquitos.
A similar virus, chikungunya, is also found in regions where Zika is prominent, and has similar symptoms. This past July, senior Sarah Sherwin contracted chikungunya when she traveled to Nicaragua on a trip with Global Glimpse.
“The symptoms I had were extreme tiredness, my joints were really tired and sore, I had a mild cold, a fever and once I got back to the U.S. I began to get a rash that covered most of my arms and legs,” Sherwin said. “I didn’t get severe symptoms until back in the U.S., but my friend […] also had it and was diagnosed by a doctor in Nicaragua. I knew I had it once I got the exact same symptoms as her.”
Zika can be spread from human to human through the bites of Aedes and through sexual intercourse. Zika’s main threat has been to pregnant mothers.
Microcephaly, a birth defect which is defined by a small head and small brain in newborn infants, has been reported at high rates in areas with active Zika transmission, and evidence is growing that Zika may be the cause.
“Scientists suspect that Zika virus may cause microcephaly, but at this point, a causation has not been proven,” said Lark Coffey, Assistant Professor in the Department of Pathology, Microbiology and Immunology at UC Davis. “More studies in pregnant women and their infants and animal models of human disease will help determine causation.”
Although cases have been tracked and recorded more readily than ever before in these Latin American countries, no cases originating from transmission have been reported and recorded in the United States at the moment. There is no evidence that Zika virus has been transmitted in California, and all reported cases have been people infected while out of the country.
The California Department of Public Health says Zika is less likely to be transmitted in the United States than in other countries.
“Because of housing conditions, water management and mosquito control practices in California, there is generally much less contact between humans and Aedes mosquitoes than in other countries,” said Gil Chavez, Deputy Director and state epidemiologist at the California Department of Public Health. “While there have been small clusters of local transmission of other diseases transmitted by Aedes mosquitoes [such as] dengue and chikungunya in other U.S. states, there has not been widespread transmission.”
Chavez stresses the importance of avoiding mosquito bites when in areas with active Zika, dengue and chikungunya transmission.
“It is very important that Californians avoid mosquito bites while traveling to affected areas to prevent these illnesses and their importation to California,” he said. “It is also important that California residents, particularly those living in counties where the Aedes mosquito has been found, avoid being bitten by mosquitoes.”
Coffey says it is difficult to determine why Zika became prominent in the past year.
“Most likely Zika virus was simply not introduced from Africa or Asia into the Americas prior to 2015,” she said. “Infected people and mosquitoes carry it, so maybe they just didn’t bring it into the Americas prior to recently. An alternate possibility is that it was introduced earlier but didn’t amplify to epidemic levels or went undetected.”
The fear is that if not reported and recorded, these cases may lead to transmission of Zika from human to mosquito to another host. Another concern arises from the fact that the virus is a highly mutable RNA virus.
“When it replicates, because the viral polymerase that copies the genome cannot error-correct, it makes on average one mutation per replication cycle,” Coffey explained. “This high mutability results in high adaptability…the capacity to change over time. A capacity to change can result in adaptation to new hosts or modified disease in people.”
Davis is currently in a zone under “invasive mosquito surveillance,” but neither Aedes aegypti nor Aedes albopictus have been detected here.
The California Department of Public Health provides various cautionary advice for people planning on traveling to countries with active Zika transmission.