A second round of aerial mosquito spraying is set to be conducted in two areas of Rhode Island this week as part of an effort to prevent additional cases of Eastern equine encephalitis.

One of the areas contains all of West Warwick as well as parts of Cranston, Warwick, East Greenwich, West Greenwich, Coventry and Scituate. A large portion of this area was included in the first round of spraying that took place earlier this month.

The other area is centered in Westerly and included parts of Charlestown, Hopkinton, Richmond and South Kingstown.

“The areas to be sprayed have been identified using several factors, including information about new human cases of EEE, cases of EEE in non-human mammals, positive mosquito samples in Rhode Island and in neighboring states, and information about the habitats in which mosquitoes most readily breed,” reads a joint statement from the departments of Health and Environmental Management.

The new spraying plans were unveiled after health officials announced on Sept. 17 that two more Rhode Islanders – a 10-year-old from Coventry and a Charlestown resident in their 50s – have been diagnosed with EEE. Both are believed to have contracted the illness in late August and have been released from the hospital.

The first person in Rhode Island diagnosed with EEE this year – a West Warwick resident over the age of 50 – died on Sept. 9.

In addition to the diagnoses in people, officials said a deer in Exeter was found to have EEE this week. A horse in Westerly was diagnosed with the disease late last month.

“This has been a year with significantly elevated EEE activity, and mosquitoes will remain a threat in Rhode Island until our first hard frost, which is still several weeks out,” Ana Novais, deputy director of the health department, said in a statement.

The new round of spraying was initially scheduled for Monday night, but officials advised Monday that it would instead likely take place either tonight or Wednesday based on weather conditions. Calm conditions and temperatures above 58 degrees are required for aerial spraying.

The advisory issued Monday reads: “Spraying here will begin as soon as the aviation company that the state has contracted with can return to Rhode Island after completing in-progress work in Massachusetts and the weather is suitable for spraying operations here. [Monday night’s] forecast calls for rain and winds up to 15 to 20 MPH, which means the flight crew might not finish spraying Massachusetts tonight and will likely finish tomorrow night. This would result in spraying beginning in Rhode Island on Wednesday.”

As in the first round of spraying, the pesticide to be used was listed as Anvil 10+10. The first round of spraying resulted in the treatment of 115,179 acres, according to the state, and approximately six-tenths of an ounce of the aerosolized version of the pesticide was used for each acre.

Officials said no spraying would take place over fish hatcheries, certified organic farms, drinking water supplies, open bodies of water or coastal areas.

“The Commonwealth of Massachusetts has used this same pesticide when spraying this year,” a statement reads. “No adverse health risks are expected with this product’s use for mosquito control. However, it is generally good for people to limit their exposure to pesticides. While spraying is occurring, it is best to err on the side of caution and limit time outdoors and keep windows closed. DEM and RIDOH will work with the Rhode Island Emergency Management Agency to urge the 12 affected communities to activate ‘code red’ alerts to update residents with this information, and additional information about spraying.”

Health officials describe EEE as a “rare but serious” illness that can affect people of all ages and is spread through mosquito bites. Symptoms of the illness include headache, high fever, chills and vomiting, which can progress into seizures and coma. Swelling of the brain can also occur, and the disease proves fatal in roughly 30 percent of cases, according to the Centers for Disease Control and Prevention.

“The foundation of all risk reduction remains personal protection (mosquito repellent, long sleeves and pants, avoiding outdoor activities between dusk and dawn, repairing window and door screens, and dumping standing water),” a statement from health officials reads. “If possible, people should limit their time outdoors at sunrise and sunset. If they are going to be out, people should wear long sleeves and pants and use bug spray. Aerial spraying effectively reduces the risk of mosquito-borne disease but if does not eliminate the risk completely. In addition, fewer mosquitoes are active as evening temperatures get cooler, but those mosquitoes that are active are more likely to be infected with EEE.”