Another “yellow fever mosquito” has been found in Chula Vista, near the place where the potentially dangerous mosquitoes were found last October.

The Aedes aegypti mosquito was discovered in an office in Chula Vista, the first such one discovered this year. Four of the mosquitoes were found last fall in offices on Naval Base San Diego and also at a Chula Vista home.

At total of nine mosquitoes and two larvae sources have emerged since last October, according to county environmental officials.

The tropical disease that the mosquito is best known for carrying are rarely seen here: yellow fever, chikungunya and dengue fever. There hasn’t been an outbreak of yellow fever in the United States in more than a century, according to the county.

Still, health officials want to prevent the spread of these potentially dangerous mosquitoes and have been putting up and monitoring traps for them.

Yellow fever mosquitoes are more common on the East Coast but started appearing in California in 2013, officials said. The mosquitoes have recently been found in Commerce and Pico Rivera in Los Angeles County.

Unlike native California mosquitoes, these insects feed during the day. They can breed almost anywhere there’s standing water, including indoors, according to the county.

To help prevent mosquito breeding, the county is urging residents to dump out anything that can hold water – such as plant saucers, buckets or wheelbarrows – and report any standing water or dead birds to Vector Control.