Assessments are the district's only source of income. If voters approve the hike, which requires only a simple majority, the vector control district hopes to raise an additional $4 million for this year's budget.

The amount of increase will vary according to the type of property being assessed. For single-family homes the assessment will go from $5.08 to $13.44, an increase of $8.36. The last assessment hike was in 1996.

In contrast to property taxes, funds raised through assessments are dedicated specifically for the purpose they were raised.

"This money will only go to vector control," said Kriss Costa, communications specialist with the Santa Clara County Vector Control District. "No one else can get their hands on it."

The mail­only ballots were sent out to residential and commercial property owners last week. They must be returned to C.G. Uhlenberg, Santa Clara County Vector Control District, 333 Twin Dolphin Drive Suite 230, Redwood City, CA 94065 by June 21. Ballots can also be hand-delivered to the vector control district office at 976 Lenzen Ave., San Jose, 95126.

The district is currently operating with a budget shortfall and is tapping into its reserves. It has revenue of $2.7 million with a budget of $3.3 million.

Without the hike, the district will find it difficult to deal with what is expected to be a heavier and longer mosquito season this summer, Costa said. The abundance of rain and mild temperatures have created ideal breeding conditions for mosquitoes, which carry the virus.

"All the experts in the state say that this year Northern California and Silicon Valley will be the epicenter of the West Nile virus epidemic," she said. "It'll look like Southern California did last year."

She said Southern California had 800 cases of the disease and 28 deaths last year.