A woman in her 30s who lives in Middlesex County is the ninth Massachusetts resident infected this year with West Nile virus, state health officials said Wednesday. The woman has recovered from the illness. The Department of Public Health also reported that it has raised the West Nile virus threat level to “critical” in Chicopee and to “high” in Granby, Holyoke, Springfield, South Hadley, and West Springfield, after a horse in Hampden County was found infected with the virus, which is spread by mosquitoes. Mosquitoes infected with West Nile have been found in 101 cities and towns in nine counties this year. Six human cases were reported all of last year.