A seventh person has contracted rat lungworm disease in Hawaii this year, the national Centers of Disease Control and Prevention confirms.

The adult fell ill in June while traveling on the west side of the Big Island and did not seek medical care until a month later after feeling symptoms of dizziness. The U.S. mainland hospital was unable to identify the source of infection, and this CDC laboratory confirmation comes nearly four months later.

The patient reported eating unwashed produce and herbs without washing them first, according to the Hawaii Department of Health.

Also known as angiostrongyliasis, rat lungworm disease has most often affected people in Hawaii who accidentally consumed small snails or slugs already infected with the parasitic roundworm. They can be hard to see, and any fresh fruits or vegetables should be thoroughly rinsed and inspected, according to Sarah Park, Hawaii state epidemiologist.

“When in doubt, cooking food by boiling for 3 to 5 minutes or heating to an internal temperature of 165 degrees Fahrenheit for at least 15 seconds can kill the parasite that causes rat lungworm disease,” she said.

This visitor was the fourth tourist to be diagnosed with rat lungworm by the CDC this year. Three other Hawaii residents were confirmed to have the disease this year.

Symptoms have varied, but most have included severe headaches and stiffness in the neck. Patients may experience debilitating effects on their brain and spinal cord, which can cause neurological problems, severe pain and long-term disability.