Compared with previous years, "we're definitely better off," said program spokeswoman Amanda Witman. But she cautioned that the situation could "change on a dot."
"We're coming into the time of year where we will see the number get exponentially higher," she said, adding that the severity of the season is "extremely hard to predict."
In Bucks County the new positives were found from samples tested in Bristol Township and Morrisville Borough; in Delaware County, the City of Chester, and in Montgomery County, Abington Township.
Of the 64 positive samples, 13 have been found in the five-county region, according to the state.
West Nile virus is a mosquito-borne disease that, in extreme cases, can result in encephalitis. First detected in New York in 1999, it showed up in Pennsylvania the following year.
In 2013, there were 11 cases reported in humans across Pennsylvania. In Montgomery County, three people tested positive. There were two in Delaware County and one in Bucks County, but none in Chester County.
To prevent the spread of the virus, officials suggest eliminating standing water when possible by making sure that rain gutters are clean and that tires, tin cans, plastic containers, and pots are kept dry. They advise turning over wading pools, wheelbarrows, and birdbaths when not in use.