Whooping cough is causing the worst epidemic seen in the United States in more than 50 years, health officials said Thursday, and they’re calling for mass vaccination of adults.

The epidemic has killed nine babies so far and babies are by far the most vulnerable to the disease, also known as pertussis, the U.S. Centers for Disease Control and Prevention says. The best way to protect them is to vaccinate the adults around them, and to vaccinate pregnant women so their babies are born with some immunity.

“As of today, nationwide nearly 18,000 cases have been reported to the CDC,” the CDC’s Dr. Anne Schuchat told reporters in a conference call. “That is nearly twice as many as reported last year. We may be on track for a record high pertussis rate this year,” she added.

“We may need to go back to 1959 to find as many cases. I think there may be more coming to a place near you.”

The last record year was 2010, when 27,000 cases were reported and 27 people died. In 1959, 40,000 cases were reported.

In 2008, whooping cough killed 195,000 people globally, according to the World Health Organization.

Whooping cough is caused by a bacterial infection. It gets its name from the nagging cough it causes that can make children breathless. They often gasp for air, making a distinctive whooping sound. But it’s not so serious in adults and they may not realize that a persistent cough is being caused by pertussis.

Related: Obesity may increase adults' whooping cough risk

Washington state is having an especially bad time with whooping cough this year, with 3,000 cases so far, compared to 20 at the same time last year, said Mary Selecky, secretary of the Washington State Department of Health.  “For every case that we know about, we suspect that there are many people out there who have pertussis and don’t know it,’ Selecky said.

“In many cases, babies get this illness from their mothers or others close to them. It’s absolutely tragic.”

The state has distributed 27,000 doses of a booster vaccine for uninsured adults and has ordered more.  “This disease is very easy to catch,” Selecky said. “It has certainly gotten hold of our population in Washington state.”

The CDC is trying to figure out what's going on, but Schuchat said a couple of factors are clearly at work. The formulation for the whooping cough vaccine was changed in 1997, and kids hitting age 13 and 14 now are the first to have been fully vaccinated with five doses of the new vaccine. The new formulation causes less of a reaction, but it may also wear off sooner, Schuchat said.

The older vaccine was made using a whole pertussis bacterium. It was very effective, but it did cause swelling in some kids who got it, and sometimes caused a fever -- something that scared parents. It also was widely blamed for causing rare but serious neurological reactions, although Schuchat said studies have not confirmed this.

“Vaccines have done a good job of reducing the incidence of pertussis but our vaccines aren’t perfect,” Schuchat said. “We wish we had better ways of controlling pertussis. Given how dangerous pertussis is for babies, preventing infection in babies is our priority.”

Schuchat says people who are not vaccinated have eight times the risk of infection compared to people who are fully vaccinated against whooping cough. And if someone who’s been vaccinated does get whooping cough, the disease is usually less serious and they are far less likely to infect someone else.

The CDC says 95 percent of toddlers aged up to three years have received at least three doses of the vaccine and 84 percent have four doses. And in 2010 69 percent of 13- to 17-year-olds got a fifth booster dose. Kids should get five doses to be fully protected.

And while adults are supposed to have at least one dose of whooping cough vaccine, only 8.2 percent of U.S. adults have done so.

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The U.S. is on course for a record year for whooping cough, health officials said this week. And while vaccinating kids is clearly the most important defense, health experts say adults may not realize they’re supposed to be getting regular shots, too.

Whooping cough, also known as pertussis, is a bacterial infection best known for causing a deep cough in children. They cough so long and so hard that when they can finally catch a breath, they make a distinctive “whoop” sound on the intake. So far this year, the United States has seen more than 16,000 validated cases of whooping cough, said Stacey Martin, an epidemiologist with the Centers for Disease Control and Prevention.

That’s more than the 15,216 cases reported last year. The latest peak was 27,550 cases in 2010, when it killed 27 people, 25 of them babies.

“We are on track to have a record year, I think,” Martin said in a telephone interview.

Pertussis has reached epidemic levels in the state of Washington, with more than 2,700 cases so far this year, and CDC is following outbreaks in 18 other states: Wisconsin, Minnesota, New York, New Jersey, Illinois, Idaho, Montana, Texas, Ohio, Iowa, Missouri, Florida, Arizona, Maine, New Mexico, Pennsylvania, Kansas, and Oregon.

"This time last year we had about 200 cases, which was a lot," said Tim Church, a spokesman for the Washington state department of health. "So to have 2,700 this time is just the most we have seen in my lifetime."

The problem is caused by a number of factors. Babies less than two months old are too young to get the vaccine, so they are especially vulnerable. And the formulation of the vaccine was changed in the 1990s to make it safer, but that also made it a little less effective, Martin said.

“We went to safer vaccine with fewer side effects but the duration of protection is not as good,” she said. Church adds that in Washington state, many parents have opted not to have their children vaccinated -- another factor that could affect the epidemic, although he said there is not data to demonstrate just how badly.

The good news is that 95 percent of U.S. children are vaccinated, Martin says. The bad news is that only 10 percent of adults are.

Children need five doses by age 6 to be fully protected and even then they may need a booster in their teens. Every adult should get at least one dose of the combined tetanus, diphtheria and pertussis vaccine, CDC says in its latest guidelines. The Infectious Diseases Society of America recommends the shot once every 10 years. 

"That’s been our big push in Washington state -- to help adults understand they need to get vaccinated too," Church said.

This is extra-confusing because there are several vaccines on the market, some of which contain just tetanus and diphtheria and some that also protect against pertussis, said Dr. Kathryn Edwards, who directs the Vaccine Research Program at Vanderbilt University in Nashville and who is a board member of the Infectious Diseases Society of America.

To protect the youngest babies, pregnant women should be vaccinated in the later stages of pregnancy, the CDC says. “I think it is hard to vaccinate pregnant women, because pregnant women have this feeling that they aren’t supposed to put anything in their body,” Edwards says. While this is understandable, studies have shown it’s very safe and the mothers-to-be pass on their immunity to their newborns, she said. This is the same for flu, too.

Even health experts often don’t realize the need for adults to be vaccinated. Edwards and colleagues surveyed 1,800 health care workers in 2007, and only 13 percent planned to get a whooping cough shot, with most saying they were unaware they even needed one. Half the time, when babies get whooping cough, a parent is the source, Edwards said. And whooping cough can make adults very sick, as well.

“Adults get whooping cough, and they cough and cough,” Edwards said. The cough can persist for weeks, but doctors and patients alike often don’t even think to check for pertussis. “Certainly, whenever adults need their booster for tetanus and diphtheria, they should include pertussis,” Edwards advised.

It’s not just whooping cough that adults need to be vaccinated against.

The CDC just released updated its adult vaccination recommendations to say adults should think about getting vaccines to prevent a range of diseases: chickenpox; measles, mumps and rubella (German measles); influenza (every single year); hepatitis A and B; and meningitis. Younger adults also need vaccinations against HPV or human papillomavirus, which causes cervical, penis and head and neck cancers (after about age 26 it’s too late), while adults older than 60 need a dose of vaccine against shingles and also should get a shot that protects against a batch of bacterial infections called pneumococcal diseases every five years.

More on Vitals: 

• Big jump seen in Oregon parents delaying vaccines
• Calif. cuts whooping cough deaths to zero
• Extra whooping cough booster might protect more kids

Dr. Tyeese Gaines, an emergency medicine physician and health editor for theGrio.com, answers your questions about everything from shingles to concussions. Got a question you'd like her to answer in an upcoming column? Send it to askdoctorty@gmail.com.

Q: Is it normal for a child to develop a food allergy all of a sudden (in this case, shellfish)?
- Elizabeth C.
A: Yes. Allergies can develop at any time. They’re more likely to start in childhood, but anyone -- even adults -- can become allergic to foods that that person has eaten his or her entire life.

Q: I’m pregnant with our second child and due in August. Both my obstetrician and my son’s pediatrician recommend that my husband and I get a pertussis booster shot (for whooping cough).  My husband was in the ER and given a tetanus shot. Do all tetanus shots come with pertussis in them?
- Sarah D. J.
A: No. There are vaccines with tetanus alone, and others with both tetanus and pertussis. We get excited about pertussis vaccination because pertussis -- the bacteria that causes whooping cough -- is highly contagious and dangerous to infants. The current recommendation is to give pertussis when adults get tetanus vaccines because it decreases the chances of adults passing pertussis onto the children.

Q: Why is it that when I go to the emergency room for a mega migraine everyone assumes I am a pill popper or drug addict? If I wasn’t in such unbearable pain and vomiting, I wouldn’t go.
- Aron B.
A: Unfortunately, there are people looking for prescription pain medication for the wrong reasons -- not because they have pain, but because they either want to get a euphoric high or sell the pills illegally. The problem is, it can be difficult to tell the difference. If you have two patients writhing in pain, but one is being deceptive, how do you know? And, in your case, patients who come in frequently do tend to raise flags. The best thing to do is get a good primary physician who knows you well. Either he or she can prescribe you pain medication and help you avoid the emergency room altogether or that physician can call the ER and “vouch” for you and the fact that you’re not drug-seeking. 

Q: Black spots keep coming up on my face, and my neck is darker than the rest of my body, what can I do to clear it up?
- Nic-nak J.
A: The neck can be darker than the rest of the body, especially in the folds, in a condition called acanthosis nigricans. Sometimes, it is benign, other times it means there is an underlying health problem. Acanthosis nigricans affects people of African descent more often, and tends to run in families. Obesity and other hormonal problems can lead to this discoloration. And, it is often seen in obesity-related diabetes -- sometimes as a warning sign long before the patient develops diabetes.  The darker discoloration can spread to the armpits, groin and finger joints. It fades once the underlying cause is treated.

The spots that appear on the skin with age are usually signs of long-term sun damage. It also appears to be related to genetics. Visit your physician or a dermatologist to figure out whether those are aging spots or discoloration to be concerned about.

Q: I am not a drinker. I may have a drink once or twice a month. Sometimes, when I drink, I get the “blood pressure headache.” Is it safe to pop another pill prior to having a drink in order to control my blood pressure?
- Lynn E. P.
A: This concept of people developing a headache when their blood pressure is high is often debated. The problem is, pain can increase a person’s blood pressure, so simply having a headache can make one’s blood pressure go up. If the blood pressure is taken at that point, who knows which caused which?

With respect to your headache, some people do develop headaches when drinking alcohol. Some are very sensitive to the dehydration that comes with even a small amount of alcohol intake. Others are affected by the chemicals in certain types of alcohol, such as red wine -- a well-known trigger in migraine sufferers.

Talk to your doctor and don’t assume that taking an extra blood pressure pill will prevent the headache. It may not be caused by your blood pressure at all.

Q: If it’s late at night, or on a weekend, can you help parents decide if they should take their child to the ER as opposed to calling their on-call pediatrician or waiting until office hours?
- Michelle V. S.
A: If the child is having difficulty breathing, or some other life-threatening condition, call 911 immediately. Otherwise, call the pediatrician. There is always someone on call for their patients. The truth is, many pediatric ER visits can wait until the morning when the pediatrician’s office is open. Allow the doctor to help with that decision. He or she may even call in the prescriptions you need to the pharmacy without you having to come in.

Dr. Tyeese Gaines is a physician-journalist with over 10 years of print and broadcast experience, now serving as health editor for theGrio.com. Dr. Ty is also a practicing emergency medicine physician in New Jersey. Follow her on twitter at @doctorty.

Note: The information included in this post is for educational purposes only. It is not intended nor implied to be a substitute for professional medical advice. The reader should always consult his or her healthcare provider with questions. Reading the information on this website does not create a physician-patient relationship.

More from Dr. Tyeese Gaines:

The doctor is in: Shingles, teen concussion and an itchy breast

An increasing number of parents may be choosing to delay or limit certain vaccinations for their young children, a new study shows, even as cases of pertussis, or whooping cough, continue to rise nationwide, with recent outbreaks in California and Washington.

The study, which examined medical records for 97,711 Portland children, found an almost four-fold increase between 2006 and 2009 in the percentage of parents who delayed or skipped vaccinations, researchers reported in the journal Pediatrics. Experts say that by delaying certain vaccinations, parents may be putting their children -- and those of others -- at a far greater risk of contracting deadly diseases, such as pneumonia and pertussis.

The new study examined the vaccination histories of children born in the Portland area between 2003 and 2009. Between 2006 and 2009, the number of parents who rejected government recommendations and made up their own vaccine schedules rose from 2.5 percent to 9.5 percent.

While the researchers could not say how typical the Portland results are compared to other areas around the country -- Portland schools reportedly have some of the highest vaccine exemption rates in the U.S. --  a 2011 study published in Pediatrics found that 13 percent of parents nationwide were using alternative schedules. Another study published in Public Health Report in 2010 found that almost 22 percent of parents were deviating in some way from the CDC's recommendations for infant vaccinations -- either by delaying shots, leaving out certain vaccines, or skipping vaccinations altogether.

The vaccine delays may not completely explain recent whooping cough outbreaks in states such as California and Washington, but “they certainly don’t help,” said Dr. Jaime Deville, a UCLA professor of infectious diseases in the pediatrics department.

The main reason parents give for delaying shots is fear their children will be harmed by receiving multiple vaccines at the same time, according to the study’s lead author, Steve Robison, an epidemiologist at the Oregon Health Authority. The vaccines most likely to be delayed by 9 months were for hepatitis B and pneumococcal disease (pneumonia).

For example, at both the two- and six-month visits the CDC recommends kids get a total of six vaccines. Even with some of them combined that adds up to a lot of shots. By age 4, children receive up to 28 vaccinations, based on the CDC immunization schedule.

Some parents believe they’ll get the same benefit if they spread the vaccinations out over more doctors’ visits rather than getting them all at once.

“There are rumors out there that your body can’t handle that many vaccines, that your body won’t be able to respond appropriately if you get several all at one time,” Robison said.

Experts say vaccines pose no harm to babies; even though multiple shots can be painful for a few moments, they say the consequences of delaying vaccinations can be much worse.

There are reasons for concern over the delayed vaccines. According to the Centers for Disease Control and Prevention there were 2,325 cases of pertussis in Washington state through June 9, 2012, compared to 171 during the same time period in 2011. A 2010 outbreak in California led to 9,143 cases -- including 10 infant deaths --  the most cases in that state since 1947.

"We’d like parents to know that the recommended number of doses of a vaccine is what is needed to build adequate protection levels both for their child and for the community," Robison said. "One dose of a vaccine, such as for pertussis, doesn’t build enough protection."

By 9 months, infants on an alternative vaccine schedule had fewer injections than those with parents following the government recommended schedule -- an average of 6.4 versus 10.4 shots -- and more doctors’ visits for vaccinations.

What’s more, few had caught up with the recommended number of vaccinations by the end of the study.

One big problem with the modified schedule is that parents are bringing children who haven’t been appropriately vaccinated into the doctor’s office more often  -- thus putting other kids at greater risk, said pediatrician Dr. Andrew Nowalk, an assistant professor at the Children’s Hospital of Pittsburgh at the University of Pittsburgh Medical Center.

Deville is especially concerned about parents who are choosing to delay the pneumococcal vaccine until age 2. Infants are most vulnerable to pneumonia during the first year of life. "Parents who delay the vaccine until age 2 are leaving their children vulnerable during the period where it occurs at its highest frequency,” Deville said.

An added advantage of the pneumococcal vaccine is that it lowers the amount of bacteria living in kids’ noses and throats, Nowalk said. “So the children who aren’t getting vaccinated are more likely to be carrying the bacteria without being infected and spreading it to others,” he added. “When you don’t vaccinate your child you’re not only putting your child at risk but also those of others.”

Further, Nowalk said, there are lots of kids out there with immune deficiencies -- those with leukemia, or depressed immune systems because of organ transplants, for example -- who can't get vaccines. So they have to rely on everyone else getting vaccinated.

“When enough of the population is immunized, transmission is essentially stopped,” Deville explained. “The bottom line is that immunizations are extremely safe. They have the most value of any of our interventions when it comes to prolonging life and preventing diseases – not only for our own children but also for the community.”

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