Whooping cough has returned with a vengeance, and Californians are feeling its brute force. Last week whooping cough, or pertussis, was officially named an epidemic in California by the California Department of Public Health.

As of June 10, there have been 3,458 cases of whooping cough reported in California, according to a statement released by the CDPH which is more than all the cases reported in 2013. More than 800 new cases were reported in just the last two weeks, and the Centers for Disease Control and Prevention says there have been nearly 10,000 cases—including two infant deaths—reported this year nationwide. That may sound pretty bad, but the actual truth may be even worse since many believe less than 10 percent of all cases ever get reported.

An epidemic? Of whooping cough? Isn’t that something our grandparents had to worry about? You know, back before they had vaccines? Sadly, it’s true. The disease that was more or less eradicated in the United States is making a comeback, thanks to all those genius parents that think vaccinations are worse than the diseases they prevent. Of course that’s mostly coming from people who never suffered from the illnesses thanks to their own vaccinations.

Regardless of the reason, whooping cough is here. Since whooping cough can be serious business, here’s what you need to know about it, how it spreads and how to prevent it.

Why Is It Spreading Now, And Who Is At Risk?

Pertussis is a cyclical epidemic, and it peaks every three to five years. The last serious bout of whooping cough came in 2010, so another peak seems imminent. It’s also a highly-infectious bacterial disease that is easily spread through — what else — a vicious cough, which is why it’s so easy for it to spread so rapidly. Both children and adults can contract it, making it even easier for contamination to happen within families and other large groups of people, like schools or community groups. The CDPH says that infants too young to be immunized are the most vulnerable to severe and fatal cases of pertussis, and two-thirds of pertussis hospitalizations have been children aged four months or younger.

What Caused The Epidemic?

Although whooping cough is cyclical, as mentioned above, instances have soared in recent years, much due to parents foregoing their children’s vaccinations. Studies show that unvaccinated children are eight times more likely to contract the illness when compared to children who received the vaccine. And it’s certainly making a difference. In fact, 2012 saw 48,277 cases—the largest number in 50 years. According to the CDC, parents who choose not to vaccinate their children have already driven a measles outbreak across the United States. Still, some studies indicate the pertussis epidemic is only in part due to nonvaccinated children. The other culprit? The current whooping cough vaccine—Dtap—which has been in use since the 90s, is only strong enough to protect against the illness for a few years. Therefore, it is now recommended to receive a second vaccination—a booster shot—even for those who have already been infected with pertussis, since the illness does not leave its host with lifelong immunity the way the chicken pox and measles viruses do. Once a person contracts whooping cough, he or she can get the illness again after just 10 years.

How To Spot Whooping Cough

According to the CDC, pertussis generally starts with cold-like symptoms, a mild cough and possibly a fever. But after one to two weeks, it progresses to severe coughing. The violent, rapid and continuous coughing can leave the lungs starved for air, causing the ill to inhale with a loud “whooping” sound. The coughing can also induce vomiting and leave the ill extremely tired. The series of coughing fits, in fact, can continue for weeks—the Chinese refer to the disease as the “100-day cough.” Pertussis is most dangerous to infants, who may not even develop a cough, but may have a more dangerous symptom known as apnea, which indicates a pause in the child’s breathing pattern.

How Can You Prevent It?

Regardless what a faction of parents may claim, the easiest and singularly most effective way of preventing whooping cough is to be vaccinated. The Tdap vaccine, which also protects against tetanus and diphtheria, can be administered to pregnant women to protect their infants who are too young to receive the vaccination themselves. At six weeks old, infants are old enough to be vaccinated individually. Older children and adults can all receive this vaccination, and it comes highly recommended if you will be around newborns in any form or fashion. Doctors say that it’s the most efficient way to fight against the highly contagious and dangerous disease. Still unsure the vaccination might cause something worse than what it prevents? Let’s put it this way: What’s worse than death?