Four more people have come down with the measles, according to the Department of Health in Pinellas County, adding to three cases announced by officials earlier this month.

Before the first case was announced on Aug. 13, there had been no cases of measles in the county for 20 years. The total number of people infected now stands at seven. None of them had been vaccinated, the health department said.

Some were related to another infected person who had traveled internationally, one of the most common ways to contract the disease.

PREVIOUS COVERAGE: In Pinellas, three cases of the measles revive concerns about those who don't vaccinate

Health officials conducted interviews at doctor's offices, schools and other places where people had come in contact with those who were initially infected. The four new cases were identified after the unvaccinated people were no longer contagious, said Maggie Hall, a spokeswoman with the health department.

The department's investigation will continue.

The disease had once been eradicated in the United States through immunizations, but as some groups have challenged the necessity and safety of routine vaccinations, it has returned in certain places.

Some parents believe there is a link between vaccinations and autism, contrary to prevailing scientific findings. Health officials strongly urge people to get vaccinated if they haven't been already.

"Our message continues to be that immunization is the best protection against diseases such as measles," said Dr. Ulyee Choe, an infectious disease specialist and director of the Department of Health in Pinellas.

"Measles is highly contagious and can have potentially serious health effects. We have not seen measles in 20 years in Pinellas because of the success of the safe, effective vaccines that prevents it."

Unvaccinated people who are exposed to measles may be excluded for up to 21 days from public places such as school and work where they could infect others, the department said.

Those infected with the disease will experience a fever that may spike to 105 degrees Fahrenheit, cough, runny nose and red, watery eyes. The blotchy red rash that is normally associated with the disease usually appears three to five days later.

More information about measles is available at the Florida Health Department website.