West Nile virus spread slows in U.S.

While the number of people infected with West Nile virus in the United States is on the rise, the pace of the outbreak is slowing down, according to federal health officials.

The Centers for Disease Control and Prevention announced on Wednesday that 4,891 people have contracted the disease, an increase from 4,725 a week prior. The virus killed four people in the past week, increasing the death toll from the outbreak to 223, Reuters reports.

The outbreak appears to be slowing, however, with 166 new cases reported in the past week, a decrease from 199 cases the previous week. The death toll was down as well, dropping from 36 the prior week.

"We're still seeing new cases, but we're seeing the pace slow down quite a bit," Chris Van Deusen, a spokesman for the Texas Department of State Health Services, said, according to Reuters.

More than half of the cases reported to the CDC were the severe neuroinvasive form of the disease, which can lead to complications like encephalitis and meningitis. The less severe form, West Nile Fever, is rarely deadly and causes flu-like symptoms.

More than 70 percent of the cases are concentrated in 10 states - Colorado, Nebraska, Oklahoma, Michigan, South Dakota, Illinois, Mississippi, Louisiana, California and Texas. More than a third of all cases have been reported in Texas, Reuters reports.