The Dangers of Whooping Cough (Pertussis)

Are you at risk?

Medically Reviewed by Roy Benaroch, MD on May 14, 2012
Written by Matthew Hoffman, MD
7 min read

Whoopingcough might sound like a disease from another era. But the illness, also called pertussis, is alive and well in the U.S.

Known as a childhood illness, whooping cough is actually most common in adolescents and adults. They pass whooping cough to other family members without realizing that their cold-like symptoms are really pertussis.

For siblings and spouses, catching pertussis might mean a severecough and missed work days. But when the recipient is an unvaccinated infant, whooping cough can spell serious trouble.

“Most of the severe disease and complications from pertussis occur in very young children, who either haven’t been vaccinated or haven’t completed their vaccinations yet,” says Harry Keyserling, MD, professor of pediatric infectious disease at Atlanta’s Emory University and a spokesman for the American Academy of Pediatrics. In 2012, there were 18 reported deaths from pertussis nationwide.

Most of these vulnerable children catch whooping cough from a family member at home. Although pertussis symptoms are mild in vaccinated people, it’s still highly infectious. And, mild pertussis in an adult easily becomes severe illness in an infant.

Bordetella pertussis is a bacterium that can live in the human respiratory tract. Pertussis is passed through secretions, so sneezes and coughs spread the bug around. Symptoms generally start a week or so after B. pertussis lands in the nose or mouth.

The classic course of whooping cough is rarely seen today, except in incompletely vaccinated children. In its initial phase, pertussis looks just like any of the many common colds children experience in their early years. Runny nose, sneezing, and low-grade fevers are typical.

Unlike a cold, though, pertussis infection doesn’t clear up in a week or so. The nasal congestion resolves, but is replaced by periods of intense coughing. In this second phase of pertussis, coughing fits occur once every one to two hours and are worse at night. The cough can be so severe that it can cause vomiting or passing out.

In older infants and toddlers, a gasp for air after a coughing fit can sometimes produce a loud “whoop.” Many infants younger than 6 months of age don’t have the whoop, but they may develop gagging or shortness of breath. Teens and adults also usually do not have the ‘whooping’ sound in their coughs. The intense coughing phase can last from one to 10 weeks.

Symptoms start to ease in the third stage of whooping cough, called the convalescent phase. Coughing fits become less frequent and eventually subside over a few weeks.

To a parent, a child’s coughing fits from pertussis can be disturbing to see. Children often cough themselves beet-red in the face. They may vomit or pass out after a spasm of coughing. Exhausted by coughing, small children can stop breathing for a few moments after a fit. Infants may stop feeding, resulting in weight loss or malnutrition. Hospitalization is often necessary in young children with pertussis.

Prior to the vaccine introduced in the 1950s, whooping cough was a common cause of death in young children. Since then, serious cases of pertussis have plummeted, but haven’t disappeared. If anything, whooping cough may be on the rise, experts believe.

Between 2000 and 2006, there were 156 deaths from pertussis reported to the federal government, according to Tami Skoff, MS, an epidemiologist at the CDC National Center for Immunization and Respiratory Diseases. “More than 90% of those were in children less than 1 year old,” Scoff tells WebMD. “And, fully 120 of the 156 deaths [77%] were newborns less than 1 month old.”

The vast majority of children survive whooping cough, even if unvaccinated. But Skoff tells WebMD that in children less than 1 year old, serious illness is the rule rather than the exception:

  • More than half must be hospitalized
  • More than half momentarily stop breathing
  • One in eight develop pneumonia
  • 1% have seizures

According to Keyserling, pertusssis is even more dangerous in infants under two months old:

  • Nine in 10 babies are hospitalized
  • 15% to 20% develop pneumonia
  • 2% to 4% have seizures
  • One in 100 will die from complications of pertussis

Babies in the U.S. are typically immunized against pertussis in a series of four injections: at 2 months old, 4 months old, 6 months old, and at 15 to 18 months. Until infants receive the third dose of pertussis vaccine at age 6 months, they’re particularly vulnerable to serious illness, experts say. Older children are given a fifth DTaP injection at 4 to 6 years old. And teens should receive a booster shot called Tdap at age 11.

“After that third dose, they have about 80% immunity,” says Skoff. And, if they become infected despite the vaccine, “the partial protection generally results in mild illness.”

“The real danger of pertussis is in unknowingly transmitting the illness to a vulnerable baby, either directly or through other people,” Skoff says. Most whooping cough infections in children come from family members, most of whom have no idea they have the disease, studies show.

Currently, about 80% to 90% of people in the U.S. have been vaccinated against whooping cough. No doubt many of them believe that means they’re immune to whooping cough indefinitely. But they’re not. Unlike some vaccines, which offer near-lifelong immunity, the pertussis vaccine wears off after 3-5 years.

That’s plenty of time to get children through their most vulnerable phase of life. After that, though, “it’s easy, and relatively common, to catch pertussis again,” says Keyserling.

Thanks to residual protection from the vaccine, whooping cough in adolescents and adults is usually mild. “Most often, it’s mistaken for a cold,” with a bothersome cough that lasts days to weeks after initial symptoms subside, according to Keyserling.

Serious illness or complications from whooping cough are almost unheard of in these age groups. Most people never seek medical attention. If they do, doctors may misdiagnose pertussis symptoms as bronchitis or asthma.

Despite the mildness of their illness, however, adults with pertussis are still infectious. An unvaccinated person in the household stands up to a 90% chance of catching pertussis if a family member brings the bacterial infection home.

In the rare instances when adults are diagnosed with pertussis, it’s usually after they develop a cough. But transmission is most likely to occur early in the illness, during the sniffling that’s indistinguishable from a common cold. So by the time of diagnosis, “exposure to others in the home has probably already occurred,” says Keyserling.

It can be extremely difficult to identify whooping cough in adults and vaccinated children because there may be minimal or no cold symptoms at first, and few severe coughing fits -- just an annoying cough that lasts for up to two months. Only 20% to 40% of adolescents and adults will have a “whoop.”

In unvaccinated children, whooping cough may be easier to detect because symptoms are more severe. You should suspect pertussis in your child if a seemingly normal cold develops into a severe cough after cold symptoms subside. Hearing the “whoop” suggests pertussis, but that classic whooping cough sound needn’t be present.

By testing a child’s nasal secretions, a pediatrician can potentially diagnose pertussis within a few days. The chances of correct diagnosis are highest if a child is tested during the first few weeks of cough.

Whooping cough poses little danger to children after their first birthdays, and almost no serious risk to older children and adults. But whooping cough does pose a serious danger to children under 1 year old. And even mild whooping cough in older children and adults can cause plenty of lost sleep and days missed from school and work.

For these reasons, the CDC recommends that everyone between the ages of 11 and 64 receive a pertussis booster shot. It's also recommended that pregnant women be vaccinated, preferably between 27 and 36 weeks' gestation. Called Tdap, the booster vaccine provides about 90% renewed immunity against whooping cough. Tdap booster shots also provide boosted immunity against tetanus and diphtheria.

Pertussis is treatable. The antibiotics erythromycin, azithromycin, clarithromycin, and trimethoprim/sulfamethoxazole are all effective against the Bordetella bacteria. However, by the time the cough becomes severe and pertussis typically diagnosed, antibiotic therapy may be too late to relieve the symptoms.

Treatment may not ease symptoms, but it can reduce the chance of spreading pertussis. When one person in a household is known to have whooping cough, experts recommend everyone in the home receive antibiotic treatment as well. Daycare and school contacts may also need to be treated preventively.