Human cases of West Nile virus disease are continuing to increase.

As of Tuesday, state health departments have reported at least 2,636 cases; 118 of them fatal, according to the Centers for Disease Control and Prevention.

These figures are the highest they’ve been through the second week of September for any year since 2003 in terms of total cases reported. Public health officials say aggressive random testing in 2003 boosted the overall figures for that year, but the number of severe cases in 2012 is the highest reported this time of year since West Nile virus was first detected in the U.S. in 1999.

“We still believe that this year’s outbreak is the largest to date and certainly the most serious,” said Dr. Lyle Petersen, director of the CDC’s Division of Vector-Borne Infectious Diseases.