A MUM from North Carolina in the US is warning others about a little-known mosquito-borne virus that almost killed her young son.

LoriAnne Surrett said her 6-year-old son Noah and his brothers were at their grandparents’ house when he complained of a headache, FOX News reported.

Noah was given some pain medication and he appeared better until Surrett received a phone call from her in-laws that the boy was not quite right. The grandparents called 911 and Surrett rushed to the house to see her son.

The mother wrote in a Facebook post that her son was limp and had blue lips. Officials said the boy suffered a seizure. Noah underwent blood tests, a CAT scan, a chest X-ray and a spinal tap, which revealed that he was suffering from La Crosse encephalitis.

The Centres for Disease Control and Prevention said the rare virus “is transmitted to humans by the bite of an infected mosquito.”

“Many people infected with LACV (La Crosse encephalitis) have no apparent symptoms. Among people who become ill, initial symptoms include fever, headache, nausea, vomiting, and tiredness. Some of those who become ill develop severe neuroinvasive disease (disease that affects the nervous system). Severe LACV disease often involves encephalitis (an inflammation of the brain) and can include seizures, coma, and paralysis,” the CDC said.

The mother said her son was treated at the ICU at Mission Hospital in Asheville, where he was responsive just a few times a day.

“Noah is a spunky little dude that sickness never brings him down,” Surrett wrote in a Facebook post. “So this is breaking all of our hearts.”

Surrett said her son started responding to her on Thursday, and was opening his eyes. She warned others to wear bug spray to avoid the virus.

“I don’t want to see another baby go through this,” she said. “Use bug spray on your kids, check for bites. It’s not 100 per cent preventable obviously, but do what you can to try.”

The North Carolina Department of Health and Human Services said people can avoid contracting the virus by wearing long sleeves, insect repellent and spend less time outside when mosquitoes are active.