Worry about the possibility of a measles outbreak in Arizona appears to be over, at least for now.

"This time, at least, it looks like we've dodged a bullet from this case," Arizona Department of Health Services director Will Humble writes in his director's blog.

"We haven’t found any secondary cases yet, which means Arizona may have come out of this without an outbreak."

State health officials had huge worries about an outbreak because measles is highly infectious and 90 percent of unvaccinated contacts become infected.

"While we can breathe a lucky sigh of relief, efforts now redouble to ensure that 95 percent of the population is vaccinated against measles," Humble wrote.

On an average day, 430 children – 18 every hour – die of measles worldwide. In 2011, there were an estimated 158,000 measles deaths.

Cases are rare in the U.S., but clusters of unvaccinated children are fueling a spike. Last year's caseload more than doubled over the year before.

A small but growing number of parents around the country, including Arizona, are ignoring evidence-based medicine on the effectiveness of vaccines. These parents, typically white, educated and financially stable, have very likely never seen a case of measles or its grave effects, and believe that vaccines are more harmful than the disease.