CDC Investigates Second Case of Local Zika Transmission as Researchers Discover New Potential Vector

As a second case of non—travel-related Zika infection comes to light in Florida, researchers from Brazil discover another mosquito that they believe may be spreading the virus.

On Wednesday, July 20, 2016, the Florida Department of Health (DOH) confirmed that they are working with the Centers for Disease Control and Prevention (CDC) to investigate what seems to be the first case of locally transmitted Zika infection, in Miami-Dade County. The individual had no travel history to Zika-endemic regions.

Now, a second case of non—travel-related Zika infection has been identified in Broward County, Florida. Governor Rick Scott has requested that the CDC send a medical epidemiologist to the state, in order to assist with the ongoing investigation and response to the non–travel-related Zika cases. Through their investigations, the DOH will be collecting blood and urine samples from residents and visitors, to be tested for the Zika virus.

Although the virus is known to be mainly transmitted through the bite of infected Aedes mosquitos, according to CNN, researchers from the Oswaldo Cruz Foundation (Fiocruz) now believe that a common house mosquito in Brazil, known as Culex quinquefasciatus, may be a potential vector for the virus. The scientists collected a total of 500 mosquitos from Recife, Brazil, that they grouped into 80 pools, which had between one and ten mosquitos each. Through RNA tests, mosquitos in three of 80 pools were found to carry Zika.

In two of the three groups that tested positive, mosquitos did not feed, which led scientists to believe that the mosquitos were natural carriers of the virus, and not simply infected hosts. Although the prevalence of Cx. quinquefasciatus mosquitos in Recife is 20 times greater than that of Aedes mosquitos, the study did not confirm that Cx. quiquefasciatus mosquitos had the ability to infect humans with the Zika virus.

In another recent study, CDC researchers studied Culex pipiens and Aedes triseriatus as potential vectors of the Zika virus. Through lab tests, the researchers found that plaque assays for Cx. Pipiens mosquitos tested negative, meaning that the species cannot serve as a host for the virus. On the other hand, although Ae. triseriatus mosquitos were able to become infected, they were not able to transmit the virus.

These recent discoveries are only further proof that efforts to combat Zika need not be stalled. To that end, in an exclusive interview with Contagion, Stephen Redd, MD (RADM, USPHS), Director of the office of Public Health Preparedness and Response (OPHPR) at the CDC stated, “There are scientific questions that really won’t get answered unless we have the funding. We really won’t be able to protect American people to the extent we can, from the technology standpoint, without that funding.”

Fiocruz researchers note that further studies are needed regarding the role of Cx. quinquefasciatus as a Zika vector.