Two mosquito samples collected in Hyde Park and West Roxbury tested positive for West Nile Virus— the first positive samples in Boston this summer. Mosquitoes carry West Nile Virus, which spreads to humans through bites from infected mosquitoes. The risk of transmission is low, but on Tuesday the city urged residents to take precautions.

Mosquito samples collected in six areas in Allegheny County have tested positive for West Nile Virus, according to the county's health department Friday.

On Friday evening, the Allegheny County Health Department announced that West Nile Virus had been found in mosquito samples across six Pittsburgh neighborhoods.