On May 5, the Santa Clara County Vector Control District began a campaign to notify Palo Alto residents of a species of small, invasive mosquitoes that are new to the area.

According to the University’s biosafety manager, Ellyn Segal, these Yellow Fever Mosquitoes were eradicated from an area near the San Francisco airport in 1979. However, they were discovered in Los Angeles in 2011 and first reappeared in Northern California in Fresno and San Mateo in 2013. In August, they were found in a residential area of Menlo Park, close to the Palo Alto border.

Although being bitten by one of the mosquitoes is not in itself dangerous, the species has the ability to carry pathogens foreign to the area, such as dengue, yellow fever and chikungunya. Dengue in particular can have severe effects for someone who has been previously infected with the virus.

Segal explained that residents should take the same precautions that they would against normal mosquitoes, such as wearing long sleeves and pants, using insect repellent and getting rid of standing water. However, one distinctive characteristic sets yellow fever mosquitoes apart from other species in the area.

“The difference between these mosquitoes and California mosquitos is that they are active during the day,” Segal said.

At only a quarter of an inch in size, the Yellow Fever Mosquito is also distinguishable by the white dots on its black body. Due to their small size, members of the species do not need much water to plant their eggs — a supply as small as dew on a leaf would be sufficient.

Although the species has not yet been detected in Palo Alto and all cases of dengue in the area have affected overseas travelers, the district has placed traps along the border to detect mosquito activity. The district has also requested that any sightings of the mosquitoes or daytime bites be reported to the county.