An Iowa resident is believed to have died from Lassa fever, a rare virus in the U.S. that causes one in three cases to experience permanent hearing loss and 95% of infected pregnant women to miscarry.

The patient, whose identity has not been publicly released, had recently traveled to West Africa, where the virus originated and can be found in the region's rats, health officials said.

The infected person, who returned to the United States from West Africa earlier this month, had been hospitalized in isolation at the University of Iowa Health Care Medical Center before his death.

On Monday, preliminary testing by the Nebraska Laboratory Response Network revealed that the Iowa resident tested positive for Lassa fever – which would be just the ninth known case of the viral disease in the U.S. since 1969, the year it was first documented in Lassa . Nigeria.

The U.S. Centers for Disease Control and Prevention is assisting local health authorities in identifying close contacts of the patient after they exhibited symptoms. The patient showed no symptoms during the trip, so fellow travelers will not be screened because their risk is “extremely low,” CDC officials said.

Anyone found to be in close contact with the deceased patient will be monitored by health authorities for 21 days.

Symptoms of Lassa fever can include fever, fatigue and headache in mild cases and bleeding, difficulty breathing, vomiting, facial swelling, shock and pain in the chest, back and abdomen in more severe cases, the CDC says.

Lassa fever can cause permanent hearing loss and deafness in patients in both mild and severe cases. According to the CDC, about one in three cases experience hearing loss of varying degrees.

Meanwhile, pregnant women are at serious risk if infected, with 95% of women losing their pregnancy and fetus.

Those infected with Lassa fever usually experience the first symptoms within one to three weeks of becoming infected with the viral disease.

The disease cannot be transmitted until the infected person shows symptoms or through casual contact such as hugging or shaking hands.

Although the virus is spread primarily through rodents — particularly West African multimammary rats and their feces and urine — it can be spread through contact with an infected person's bodily fluids, according to the CDC.

According to preliminary information, investigators believe that the Iowa patient had contact with the West African rats.

In West Africa, there are approximately 100,000 to 300,000 cases of Lassa fever each year, with an average of 5,000 deaths.

With post wires