Patricia Schnabel Ruppert, the health commissioner of an outlying New York suburban county, is feeling “overwhelmed.” Since October she has been waging an uphill fight to quell one of the worst US measles outbreaks in 20 years. Among her daily battles: having to constantly repeat that the vaccine does not cause other diseases, that it does not lead to autism, and that the practice of using fetal tissue to produce the vaccine ended decades ago.Pushing back against such “junk science” absorbs a good deal of her energy as she works to educate and persuade the 300,000 residents of Rockland County to cooperate with health authorities and alert them to any new cases of disease. In 27 years of practicing medicine, Ruppert said, this is “one of the most challenging health crises I have had to deal with.”As of Friday, measles — officially eliminated from the United States in 2000 — had struck 167 people in this county along the Hudson River, including nine new cases this week. Among the six regional outbreaks of measles reported by the Centers for Disease Control (CDC), the leading public health institute in the US, Rockland County’s is the most concentrated.And yet the county has not skimped in throwing resources at the problem. Unprecedented measuresSince October, each case has been systematically investigated to determine how many people have been exposed to the ultra-contagious virus.Those exposed are then contacted to ensure they have been immunized, and if they haven’t been, they are then vaccinated.Dozens of free vaccination clinics have been organized around the county — including one Friday in the town of Haverstraw — with 17,654 doses of vaccine administered to date. The objective is to raise the vaccination rate from the current 72 percent, Ruppert said. A 95 percent vaccination rate is considered necessary to prevent epidemics. On Monday, county executives will meet with legal and health professionals to identify more possible new strategies to tackle the outbreak.