Mosquito bites left a woman with a West Nile virus infection that caused facial paralysis and diarrhea for 3 months

• A woman in New Jersey experienced partial facial paralysis as a symptom of West Nile virus.
• She also reported weakness in one arm and diarrhea due to the mosquito-borne illness.

A woman in New Jersey could not move the right half of her face for months after she was bitten by mosquitoes infected with West Nile virus, according to a case report published online July 14.

West Nile virus is the most common mosquito-borne disease in the US. It's usually transmitted during summer through fall, and it sickened more than 2,600 Americans in 2021, according to the Centers for Disease Control and Prevention.

The New Jersey woman sought medical attention for persistent diarrhea and a low-grade fever in late September. She told doctors that she had received "excessive mosquito bites" on a hike before she began feeling ill, and she was discharged with antibiotics.

The next morning, she woke up dizzy and had noticeable weakness in her right arm. Although she could feel her arm was not numb or tingling, her reflexes were not responding normally upon her admission to the hospital.

Doctors did not identify the woman by name, but noted in the case report that the patient was white and in her 40s. They did not find signs of stroke, and testing for various tick- and mosquito-borne diseases came back negative before the patient was finally diagnosed with West Nile virus infection.

Most people who are infected with West Nile virus do not show symptoms of disease, according to the CDC. About one in five people with the virus get a fever with aches or gastrointestinal distress, and an even smaller portion go on to develop neurological symptoms, such as paralysis.

Facial paralysis set in two weeks later

Although the woman's fever resolved with rest and IV fluids, the weakness in her right upper arm continued. She was discharged to a rehabilitation facility after nine days in the hospital.

A week into rehab, the patient said she could not move the right half of her face, doctors wrote in the case report. She was diagnosed with Bell's palsy, a condition characterized by temporary paralysis or weakness on one side of the face.

Several different viral infections — including shingles and herpes — have been associated with temporary facial drooping, but only one case of Bell's palsy related to West Nile virus was described in medical literature before this patient.

About one in 150 West Nile virus infections escalate to cause severe neurological symptoms, including muscle weakness and paralysis, according to the CDC.

If the virus reaches the brain or spinal cord, it may cause headaches, high fevers, neck stiffness, disorientation, tremors, loss of vision, or even coma. These symptoms may resolve over several weeks or months, but some effects are permanent.

The patient in New Jersey saw her facial paralysis resolve three months after it started, but she continued to experience some gastrointestinal troubles. The muscle weakness in her right arm only improved "moderately" in comparison to the facial palsy.

West Nile virus infection is fatal in about one in 10 cases involving the central nervous system, according to the CDC. People with certain medical conditions, including cancer and diabetes, as well as people over 60 years old, have a greater risk of developing severe illness with West Nile virus infection.