An outbreak of pertussis in Albany County, N.Y., has infected 19 adolescents and adults so far this year. The county recorded just 15 cases of the illness for all of 2002. Health officials in New York are warning residents to be alert if they develop a chronic cough, because failure to treat pertussis could lead to serious complications and even death. Pertussis vaccinations are required for children; however, the vaccine is only 80 percent effective and it fades over time, according to county epidemiologist Carol Killian.