State officials plan to conduct aerial spraying of a pesticide Wednesday morning in part of the Philadelphia area to kill larval mosquitoes that could transmit the West Nile virus.

The Department of Environmental Protection said a helicopter would spray along I-95 at wastewater treatment plants near Penrose Ferry Road and the Betsy Ross Bridge, and in the wetlands east of Philadelphia International Airport.

Officials said the spraying was needed because the mosquito population could be large this year after heavy rainfall. The virus can cause humans to contract West Nile encephalitis, an infection that can result in swelling of the brain. For more information about West Nile virus and state efforts, visit www.westnile.state.pa.us. - Robert Moran