County vector control crews will begin treating San Diego area waterways Wednesday to try to eliminate mosquito larvae in an effort to reduce the risk of potential transmission of the West Nile or Zika viruses.
The aerial larvicide drops will target nearly 50 rivers, streams, ponds and other waterways in the region. According to the county, the larvicide is harmless to people and pets but kills mosquito larvae before they can turn into biting adults.
The exact number of waterways that receive drops varies, depending on whether or not they have dried up, but vector control flies over 48 areas. The drops will continue monthly through October.
RELATED: 86 People Diagnosed With Zika In San Diego
Another 1,400 potential mosquito-breeding areas each year are treated by hand. The vector control program also gives out free mosquito-eating fish to the public, tracks down and treats neglected swimming pools and tests dead birds for West Nile.
Mosquitoes breed in standing water. County officials have issued several recent calls for the public to help by dumping out water that may have gathered from the rains over the past few months, such as clogged rain gutters, overturned toys or inside old tires.
Native mosquitoes spread the West Nile virus, while an invasive form of the species is capable of carrying Zika.
However, no mosquitoes in San Diego County have tested positive for Zika, and the only locally acquired cases of the illness have been sexually transmitted, according to county health officials.
