Alternative name: pertussis
Whooping cough is an infection of the respiratory system that’s caused by infection with bacteria known as Bordetella pertussis (B. pertussis).
Whooping cough causes severe coughing in spasms or spells, which usually end with a “whooping” sound when the child breathes in at the end of the coughing spell. In some children, especially young infants under the age of 6 months, whooping cough can be a serious illness.
This illness is sometimes known as the “one hundred day cough” because of its long duration.
Children and adults who have whooping cough spread the illness by coughing and sneezing contaminated droplets, which are highly infectious. These infected droplets are breathed in by people who may be in close contact.
Once inside the airways of the lungs, the Bordetella pertussis bacteria produce toxins that interfere with the normal ability of the respiratory tract to eliminate bacteria. These bacteria also cause inflammation and damage to the lining of the airways of the lung.
Whooping cough was once considered to be a rather old-fashioned illness, only dangerous to children. Now, however, it seems to be making a comeback, not only in young children, but also in older children and adults who had been vaccinated as infants. It appears that the vaccination may start to lose its effectiveness at about 11 or 12 years, leaving older children and adults susceptible to the illness.
Whooping cough often goes undiagnosed or is misdiagnosed in both children and adults. The cough may be misdiagnosed as bronchitis or asthma.
Before the pertussis vaccine was developed in the 1940s, whooping cough killed close to
10,000 people in the United States each year. Today, the annual number of fatalities in the US has dropped to less than 30, with more than half of these being babies younger than 12 months.
During the late 1970s and early 1980s, there were many severe epidemics of whooping cough at a time when fewer babies were immunised against pertussis (many parents chose not to vaccinate their children). Also, the level of protection offered by the vaccine declines steadily during childhood and booster vaccinations are required to offer continued protection against this illness.
Bacteria known as Bordetella parapertussis cause an illness called parapertussis. This is usually a milder form of whooping cough, although the symptoms are very similar to pertussis itself.
Who gets whooping cough?
Whooping cough was one of the most common and serious childhood diseases, and a major cause of death in children (especially infants), before the pertussis vaccine was introduced in the 1930s and 1940s.
Pertussis still remains endemic throughout the world, and epidemics tend to occur every four years in most countries. Whooping cough remains a major health risk for children in non-vaccinated populations.
Natural immunity doesn’t persist for life, even after a person has had whooping cough. But repeat illnesses are uncommon, usually mild and most often go undiagnosed. Most infants are now routinely immunised against pertussis, but this immunity usually fades by about 12 years.
Once someone in a household contracts whooping cough, there’s an almost 90% likelihood of non-immune family members also contracting this illness. Infected teenagers and adults who may not be diagnosed as having the illness are regarded as the major source for spreading whooping cough to infants and children.
Whooping cough cases mainly occur in unvaccinated or incompletely vaccinated infants. Many cases however, are adolescents and adults who were previously vaccinated, but in whom protection from the pertussis vaccine has decreased over time.
Symptoms of whooping cough
Whooping cough may last from 10-12 weeks. There are three distinct stages of this illness:
1. Catarrhal stage
This stage of whooping cough resembles a cold and usually lasts 2-3 days. It starts off with sneezing, red watery eyes, and a runny nose. Loss of appetite, listlessness and a dry cough, first at night and then also during the day, are early symptoms. There’s usually no fever.
This stage is the most contagious part of the illness.
2. Paroxysmal stage
Next, the cough usually worsens after 3-4 days, with bouts of distressing coughing spasms, followed by the characteristic “whoop” at the end of a coughing spell. The bouts of coughing are often worse at night and may result in vomiting.
During these coughing bouts, a child may go red or blue in the face and stringy, white mucus may flow from the nose and mouth. Nosebleeds and small bleeds in the whites of the eye may occur due to the severity of the coughing spells.
(Source: US Centres for Disease Control and Prevention)
In infants, it’s more common to see choking spells than whooping. Severe coughing spells may make it difficult for the child to eat or drink, which is aggravated by vomiting.
3. Convalescent stage
This stage, in which symptoms start to decrease in severity, usually begins any time between 6 weeks and 3 months after the onset of the typical cough. There are less frequent and less severe coughing spells, especially during the day, and also less vomiting.
Although the coughing and other symptoms become progressively less severe, coughing at night may continue for up to 6 months in some children.
What causes whooping cough?
Whooping cough is caused by bacteria known as Bordetella pertussis. Another type of bacteria, Bordetella parapertussis, can cause a milder form of this illness.
Both Bordetella pertussis and Bordetella parapertussis spread from person to person through droplets (during sneezing and coughing), and can multiply rapidly in the lining of the mouth, nose and throat of an infected person.
Whooping cough is highly contagious, especially during the early stages for up to 2 weeks after the cough starts. In the early stages of whooping cough, an infected person may not realise that they have this illness.
Dangerous complications include acute encephalopathy (inflammation involving the brain) and bronchopneumonia (inflammation of the lungs, arising in the bronchi or bronchioles).
Risk factors for whooping cough
Any person who isn’t immune to Bordetella pertussis through vaccination or previous infection can get whooping cough at any time.
According to the National Institute for Communicable Diseases, the following groups are at increased risk for infection and severe illness:
- Babies and young children who have not been vaccinated or who are partially vaccinated.
- Individuals with a weakened immune system and those with chronic lung disease.
Note that previously vaccinated people, including older children, adolescents and adults, are also at risk of getting pertussis as the immunity provided by the vaccine diminishes over time.
Babies younger than 6 months of age are most likely to develop complications. In this group, whooping cough is a serious illness that may even be fatal.
Course and prognosis of whooping cough
Although most people recover from whooping cough within several weeks, complications can be severe.
The disease can be fatal in children younger than 6 months, especially in premature babies and those with lung disease or compromised immune systems. It’s therefore essential for all babies to have their vaccinations on time and also for boosters to be given.
In South Africa, the Expanded Programme on Immunisation (SA-EPI) schedule includes four doses of pertussis vaccine. The first series is given in three doses at 6, 10 and 14 weeks of age. A fourth booster shot is given at 18 months.
Note, however, that immunity after vaccination diminishes over time. As a result, the National Institute for Communicable Diseases recommends another booster shot at about 6 years of age to ensure adequate protection.
How is a whooping cough diagnosis made?
Early diagnosis is important, as it can help prevent the spread of the bacteria that cause whooping cough.
A doctor can confirm the diagnosis by taking special swabs from the nose and sending them to a laboratory where Bordetella pertussis bacteria can be identified.
The diagnosis can be confirmed by various methods, including:
- Bacterial culture: The samples taken from the nasal swab are allowed to grow in special culture media. For the identification of Bordetella pertussis, this process typically takes 7-10 days.
- PCR (polymerase chain reaction) testing: This molecular technique is used to detect genetic material of the pertussis bacteria.
- Serology: These are blood tests that detect pertussis antibodies.
Pertussis can sometimes be difficult to diagnose, as the initial symptoms are similar to those of the common cold or flu and other respiratory infections. If there’s any doubt, the above tests can be used. These tests are also particularly useful when a pertussis outbreak is suspected.
How is whooping cough treated?
Older children who have whooping cough don’t usually need to stay in bed if their symptoms are mild, but younger children are often feel quite ill and will want to stay in bed.
Also follow these steps:
- Make sure your child remains well hydrated because he or she may have vomiting spells with the coughing.
- Give frequent, small meals to help reduce the chance of vomiting and to help retain nutrients in the child’s body.
- Offer water, fruit juices and clear soups to help prevent dehydration.
- Steam inhalation may be beneficial for clearing the airways and to make breathing easier.
Antibiotics such as erythromycin and the newer forms of this type of antibiotic, azithromycin and clarithromycin, will eradicate the Bordetella pertussis bacteria that cause whooping cough.
Antibiotic treatment also reduces the spread of the disease to the rest of the family. Oddly enough, this antibiotic treatment doesn’t reduce the duration of the illness, but shortens the contagious period. The earlier antibiotics are started in this illness, the better the results.
Some doctors recommend giving preventive antibiotics to help stop the spread of the pertussis bacteria within the household, and also giving vaccine boosters to family members.
Up to 75% of babies younger than six months with whooping cough will require hospitalisation. Expert care is important during the critical stages of the disease, especially with infants, as spells when they may stop breathing (known as apnoea) are a major cause for concern.
About 40% of older babies with pertussis will also be hospitalised. Some of these children may develop pneumonia associated with this infection. While in hospital, an infant or child with pertussis will need suctioning of the thick respiratory mucus, and additional oxygen is often required.
When to call a doctor
It’s important to see your doctor immediately if you suspect your baby or child has whooping cough.
Also call your doctor if your child has been exposed to someone with pertussis, even if the child has already received all of the scheduled immunisations.
How can whooping cough be prevented?
Whooping cough can be successfully prevented with the new and safe acellular pertussis vaccination.
This forms part of the routine vaccination schedule for all infants at age two, three and four months, with a booster given at 18 months. Another booster is required at about 6 years and again at 12 years to prevent a drop-off in immunity to the whooping cough bacteria.
It remains important to keep babies and young children away from people who may be infected with Bordetella pertussis bacteria. Always remember that whooping cough is a highly contagious illness that’s especially dangerous for young babies.
Reviewed by Prof Eugene Weinberg, paediatrician at the UCT Allergy and Immunology Unit. May 2018.