So far this year, the number of human cases of West Nile virus in Harris County has exceeded the record set in the 2012 outbreak. "Everything is looking like it's going to be a record year, which is a big surprise," said Dr. Scott Weaver, scientific director at the Galveston National Laboratory, where emerging diseases like West Nile virus are researched. Weaver said the sudden outbreak is surprising because, with the exception of 2012, the trend has been downward for the virus since 2003. Researchers at UTMB are working with Harris County to unravel the mystery of why and where outbreaks occur, said Dr. Alan Barrett, a director of UTMB's Sealy Center for Vaccine Development. This year's outbreak could be caused by a spate of rain during the spring and summer that created ideal breeding conditions for the mosquito that transmits the virus from birds to humans, Barrett said in an emailed response to questions. Researchers at UTMB and other institutions are working on a vaccine for West Nile, but are finding human testing difficult because they never know when the disease will surface, Barrett said. There is a possibility that the U.S. Food and Drug Administration will allow the effectiveness of a vaccine to be tested in animals with subsequent testing of its safety for humans, he said.