Whooping cough is an infectious disease caused by Bordetella pertussis bacteria.
It is highly contagious and can result in serious illness.
Vaccination will successfully decrease the incidence of this disease.
The main symptom is severe bouts of spasmodic coughing with a characteristic “whoop” at the end of the coughing bouts.
Worldwide whooping cough causes 300 000 deaths per year with unimmunised children being at the greatest risk of this illness.
The medical name for whooping cough is ‘pertussis’ (per-TUS-is). Whooping cough is a highly infectious form of bronchitis and it is characterised by spasms of coughing usually ending in a high-pitched crowing sound in called the "whoop" which occurs when breathing in at the end of the intense spasms of coughing. In some children whooping cough can cause serious illness.
Children and adultswho have whooping cough spread the illness by coughing and sneezing contaminated droplets which are highly infectious. These infected droplets are breathed in by those people who may be in close contact. Once inside the airways the pertussis bacteria produce chemical toxins that interfere with the respiratory tract’s normal ability to eliminate bacteria. These bacteria also produce chemicals, causing inflammation, which damage the lining of the airways of the lungs.
Pertussis was once considered to be an 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 previously, which was thought to last a lifetime. It appears that the vaccination starts to lose its effectiveness between the ages of 5 and 10, leaving older children and adults susceptible to the illness.
Pertussis often goes undiagnosed or misdiagnosed in both children and adults, and 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 around 20, with more than half of those being babies less than one year old.
During the late 1970’s and in the 1980’s there were many severe epidemics of whooping cough when fewer babies were immunized against pertussis as their 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.
Although whooping cough is caused by Bordetella pertussis bacteria, similar bacteria known as Bordetella parapertussis, cause ‘’parapertussis’. This is usually a milder and less often fatal form of whooping cough, although the symptoms are very similar to pertussis itself.
Who has the greatest risk of getting infected?
Pertussis was one of the most common childhood diseases and a major cause of death in children before the availability of the pertussis vaccine. Pertussis is endemic throughout the world. Epidemics of whooping cough tend to occur every 4 years in most countries. Worldwide it still causes an estimated 300 000 deaths per year, and in non-vaccinated populations it remains a major health risk for children. Natural immunity does not persist for life after a person has had whooping cough, but repeat illnesses are uncommon, are usually mild and often go undiagnosed.
Most infants are now routinely immunized against pertussis, but this immunity usually fades in early adult life. If anyone in a household contracts pertussis, there is a 90% likelihood of non-immune family members contracting it too. Infected teenagers and adults, who may not be diagnosed as having the disease at first, are regarded as the major source for spreading pertussis to infants and children.
Pertussis cases mainly occur in unvaccinated or incompletely vaccinated infants. Many cases, however, are adolescents and adults who were previously vaccinated, but where protection from the pertussis vaccine has decreased over time.
Symptoms and signs
Whooping cough may last from 10 to 12 weeks. There are three distinct stages of this illness:
Catarrhal stage:This stage which resembles a cold usually lasts for 2 to 3 days, starting off with sneezing, tearing of the eyes, a runny nose and red watery eyes. Loss of appetite, listlessness and a dry cough, first at night then also during the day are early symptoms. There is usually no fever. This stage is the most contagious part of the illness.
Paroxysmal stage:The cough becomes paroxysmal after 3 to 4 days with bouts of distressing coughing spasms, followed by the characteristic whoop at the end of the coughing spell. The bouts of coughing are often worse at night and may result in vomiting. During these coughing bouts the child may go red or blue in the face and stringy white mucus often flows from the nose and mouth. Nose bleeds and small bleeds in the whites of the eye may occur due to the severity of the coughing spells. In infants it is more common to have choking spells than whooping. Severe coughing spells may make it hard for the child to eat or drink, which is aggravated by vomiting. Again there is no fever.
Convalescent stage:This usually begins at any time between 6 and 12 weeks after the onset of the typical cough, and symptoms start to decrease in severity. There are less frequent and severe coughing spells, especially during the day, also less vomiting, and the child starts to look more healthy. Although the symptoms gradually become progressively less severe, coughing at night may continue for up to 6 months in some children.
When to call your doctor
It is important to see your doctor immediately if you suspect your child has pertussis. Also, call your doctor if your child has been exposed to someone with pertussis, even if your child has already received all of the scheduled immunizations.
The doctor can confirm the diagnosis of pertussis by taking special swabs from your child’s nose and sending them to a laboratory where Bordetella pertussis bacteria are identified. Blood tests are also helpful in confirming the diagnosis, especially if a considerably increased white blood cell count is found.
Older children who have whooping cough do not necessarily need bed rest if their symptoms are mild. Because the child may have many vomiting spells, it is essential to see that he or she remains hydrated. Giving frequent small meals helps reduce the chance of vomiting and will keep nutrients in the child’s body. Water, fruit juices and clear soups help prevent dehydration. Steam inhalation can also prove beneficial for clearing the airways and facilitating breathing.
Antibiotics such as Erythromycin and 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 does not reduce the duration of the illness, but shortens the contagious period.
Some doctors recommend giving prophylactic (preventive) antibiotics to help stop the spread of the pertussis bacteria within the household, and also giving vaccine boosters to family members.
Infants with whooping cough usually require hospitalisation. Expert care is important during the critical stages of the disease, and almost all infants who are less than six months old will need hospital treatment for their illness. About 40% of older babies with pertussis will also be hospitalized. Many 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.
Previously reviewed by Dr John D. Burgess, Red Cross Children's Hospital
Reviewed by Prof Eugene Weinberg, Paediatrician, February 2011