Yuba River Charter School in Nevada County, Calif., has been shut down and quarantined after school officials learned that an unvaccinated child with measles had attended school prior to spring break.

The Nevada County Public Health Department revealed that the child had travelled overseas and became sick after returning to the United States. The child has since recovered from the illness, but since he showed symptoms while attending school earlier this month, officials decided to err on the side of caution and quarantine the campus - especially due to the contagious nature of measles which can easily be spread through air or direct contact.

Based on records, Nevada County is highly susceptible to measles, ranking among the lowest in terms of vaccination rates in California. Only 77 percent of incoming kindergartners have been fully vaccinated by the start of the 2015-2016 academic year, with YRCS being particularly vulnerable, as only 43 percent of kindergarten students are fully vaccinated.

As such, even though the school re-opened Wednesday, only students who have provided sufficient documentation of an immunity to measles will be allowed to attend classes. These documents include a documentation of at least one measles vaccination two weeks prior to March 17 (the last day the affected child attended school while showing symptoms) or later, or a blood test report showing IgG antibodies to measles.

If the infected child, or any other child for that matter, fails to present these documents then they will be barred from going to school.

Excluded students students can resume school on April 8 once the Health Officer from the Nevada County Public Health Department affirms that the period of surveying the outbreak of measles is done and no new cases of measles have sprouted in the vicinity. In the meantime, they have been urged to remain quarantined.

California is no stranger when it comes to measles. Despite the disease being declared eliminated in the U.S. in 2000, pockets of unvaccinated children have led to outbreaks in recent years including a 2015 outbreak that started in two Disney theme parks in Southern California and wound up leaving 130 people infected across the state.

That outbreak - along with several other, smaller cases from later that year - led to legislation being passed that makes it more difficult for parents to leave their childen unvaccinated. Unfortunately for YRCS, it only goes into effect for the 2016-17 school year.