Columbus Public Health on Friday reported 19 confirmed measles cases, after revising their numbers to exclude suspected cases.
The outbreak began in June with the first recorded measles case in Columbus in over 20 years.
Since then, there have been nine hospitalizations. All but one of the patients have been children under the age of 4 (one child is 6 years old).
Columbus Health Commissioner Dr. Mysheika Roberts says case numbers will likely continue to grow.
"We are doing all we can to get individuals vaccinated who need to be vaccinated," she said. "But you know, there are a lot of individuals that don't believe in this vaccine, and that's why we're in the situation we are right now."
The measles-mumps-rubella, or MMR, vaccine is not recommended for children under 12 months. Dr. Roberts said much of the spread has been in child care centers, especially those that do not separate kids by age group.
"If you have a child who has cold-like symptoms, keep them home, don't send them to daycare, don't send them to, you know, your neighbors to play. Keep them home to avoid that spread," Roberts said.
The Centers for Disease Control and Prevention is sending a team of epidemiologists who are scheduled to arrive in Columbus on Thanksgiving weekend to aid in the investigation.