- Pertussis is an infectious disease caused by Bordetella pertussis bacteria.
- It is highly contagious and can result in serious illness.
- Vaccination decreased the original incidence of the disease, but it appears to have been making a comeback since the 1980s. The cause of this is not fully understood.
- The main symptom is a paroxysmal cough, with the characteristic “whoop”.
- Worldwide it causes 300 000 deaths per year and unimmunised children are at risk of the illness.
What is pertussis?
Pertussis [per-TUS-is], commonly known as “whooping cough”, is a highly communicable bacterial disease, and it is characterised by spasmodic coughing generally ending in a high-pitched crowing called the "whoop". It is very contagious, and can result in serious illness.
People who have the disease spread it via the air by coughing and sneezing contaminated droplets. Once inside the airways, pertussis bacteria produce chemical toxins that interfere with the respiratory tract’s normal ability to eliminate germs. Pertussis bacteria also produce chemicals causing inflammation, which damage the lining of the breathing passages.
A recent history of pertussis
Pertussis was once considered to be an old-fashioned illness only a danger to children. Now, however, it seems to be making a comeback, not only with young children, but also with older children and adults who had received vaccinations previously thought to last a lifetime. It appears that the vaccination is starting to lose its effectiveness between the ages of five and 10, leaving older children and adults susceptible.
Pertussis often goes undiagnosed or misdiagnosed in adults, and the symptoms thought to be that of bronchitis, allergies or asthma. Before the vaccine was developed in the 1940s, whooping cough killed close to 10 000 people and caused 200 000 illnesses in the United States each year, according to the CDC (Centers for Disease Control). Today, the annual number of fatalities in the US has dropped to around 20, with more than half of that figure being babies less than a year old.
Doctors are puzzled at the strong comeback the disease has made since the 1980s. Some attribute it to the fact that many parents nowadays are choosing not to vaccinate their children because of the risks and side effects concerned, and others think that it is because adults are spreading the disease. Research seems to indicate, however, that the problem lies in the longevity of the vaccine’s efficacy, where anyone who received the vaccine 12 years ago or longer will have a breakdown in immunity. This is why pertussis is also an issue for adults, and health practitioners need to become aware of this trend. The need for a booster vaccine is now being studied.
What causes pertussis?
The causative agent is Bordetella pertussis, a bacterium. Another similar organism, B. parapertussis, causes parapertussis, which is usually milder and less often fatal, although it is not clinically distinguishable from Bordetella pertussis. Pertussis can be transmitted by breathing in B.pertussis after it is sprayed into the air by someone carrying the disease, usually during the catarrhal and early paroxysmal states (see "Symptoms"). It is not generally accepted that contact with contaminated articles can cause transmission of the disease.
Who gets pertussis and what are the associated risk factors?
Pertussis was one of the most common childhood diseases and a major cause of death in children before the availability of a pertussis vaccine. Pertussis is endemic throughout the world.
Worldwide it still causes an estimated 300 000 deaths per year, and in unimmunized populations it remains a major health risk for children. Natural immunity is not conferred for life after one attack, but second attacks are not very common, and are usually mild and often undiagnosed.
Most infants are now routinely immunized against pertussis, but this immunity usually fades at the onset of early adulthood. If anyone in a household contracts pertussis, there is a 90% likelihood of all non-immune family members contracting it too. Infected teenagers and adults, who are not usually even diagnosed as having the disease in the first place, are now viewed as the major source for spreading pertussis to infants and children.
Pertussis cases have been increasing since the 1980s, and most cases are unvaccinated or incompletely vaccinated infants. Many cases, however, are adolescents and adults were previously immunized, suggesting that protection from the pertussis vaccine may be decreasing over time.
What are the symptoms and signs of pertussis?
The disease lasts about six weeks, and consists of three stages. The incubation period lasts an average of seven to 14 days. The three stages of the disease are:
- Catarrhal stage: This stage begins insidiously, starting with sneezing, tearing of the eyes, running nose and cold-like symptoms. The signs are similar to that of the common cold, including nasal congestion, runny nose, red and watery eyes and dry cough. Also present are loss of appetite, listlessness and a hacking nocturnal cough, which becomes gradually more evident during the day. There is rarely a fever at this stage, and it is the most contagious stage.
- Paroxysmal stage: The cough becomes paroxysmal after about 10 – 14 days. It becomes a rapid wet cough, bringing up thick and stringy mucus, and more evident at night. It is manifested by 5 to 15 rapidly consecutive coughs, followed by the characteristic whoop and a hurried deep inspiration. A few normal breaths generally follow, and then another paroxysm. A child may become suffused (turn "red" from effort) or cyanotic (turn "blue" from lack of oxygen) during an episode. There may be vomiting subsequent to the paroxysms, which can be attributed to the tenacious mucus. In infants it is more common to have choking spells (with or without cyanosis) than whoops. Severe coughing spells may make it hard for the child to eat or drink, which is exacerbated by vomiting. Severe coughing can also result in petechiae, which are tiny red spots where blood vessels rupture at the skin’s surface. There may also be small areas of bleeding in the whites of the eyes. Fever is absent or minimal in this stage.
- Convalescent stage: This usually begins within four weeks, and is heralded by less frequent and severe paroxysms, decreased vomiting, and a generally healthier appearance. The symptoms gradually wane, but may last for another six months. With each upper respiratory infection during the next year, the child may develop a pertussis-like cough.
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.
How is pertussis diagnosed?
The doctor can confirm pertussis by growing cultures of respiratory fluid: samples of secretions from the nose or throat are taken and examined in a laboratory. Blood tests and a chest X-ray can also be done.
During the catarrhal stage it is often difficult to distinguish whooping cough from influenza or bronchitis. Cultures of nasopharyngeal (nose and throat) specimens are positive for B.pertussis in 80-90 percent of cases during the catarrhal and early paroxysmal stages.
Alternatively, specific fluorescent antibody testing of nasopharyngeal smears will accurately diagnose pertussis, but this is not as sensitive a test as the culture.
Parapertussis is differentiated by culture of the fluorescent antibody technique.
What is the outcome of pertussis?
The average duration of whooping cough is about seven weeks. There are usually two weeks of common cold symptoms, two weeks of severe coughing, and two or more weeks of convalescence. Paroxysmal coughing often recurs for months, which is commonly induced by irritation from an upper respiratory tract infection.
Pertussis is a serious disease in children under the age of two, and rarely serious (but troublesome) in older children and adults. The aged can also have a serious reaction to pertussis.
There are certain complications that tend to arise when the disease occurs in infancy, most frequently respiratory problems such as asphyxia. Another frequent and potentially fatal complication is bronchopneumonia, and this tends to occur more commonly with the elderly. Because of the increased intrathoracic pressure during paroxysms, interstitial and subcutaneous emphysema and pneumothorax can occur. If a child is debilitated, bronchiectasis and residual emphysema can result.
Middle ear infection (otitis media) is frequent with children who have pertussis. Infants can experience convulsions, but this rarely happens with older children. Very severe paroxysms and consequent anoxia (lack of oxygen) can result in hemorrhage (internal bleeding) into the brain, eyes, skin and mucous membranes.
Other complications of pertussis include apnea (temporary halt in breathing) and seizures. In extreme cases, people have been known to fracture ribs with the severity of the coughing, and develop hernias (protrusion of part of an internal organ through the wall of its containing cavity).
How is pertussis treated?
Older children who have whooping cough need not necessarily have 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.
There seem to be two main approaches regarding medication. Some doctors recommend that antibiotics should only be used in cases where bacterial complications arise, such as bronchopneumonia and otitis media. Antibiotics won’t cure whooping cough, but after five days on medication the person will no longer be contagious. Other doctors feel that antibiotics constitute normal treatment, and consider them to be most effective when given early in the course of the illness. Newer antibiotics such as azithromycin and clarithromycin cause fewer stomach upsets. The antibiotics should be given for 10 days to prevent relapse.
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. Antibiotics are also seen to shorten the contagious period of the disease.
Seriously ill infants must be kept in a quiet, dark room, and disturbed as little as possible. Any stimulation can precipitate serious paroxysmal spells with anoxia. Generally it is recommended that seriously ill infants be hospitalised, because expert care is important during the critical stages of the disease, and almost all infants who are less than six months old receive hospital treatment for their illness. About 40% of older babies with pertussis will also be hospitalized. Many of these children have pneumonia associated with this infection. While in hospital, a child with pertussis might need suctioning of thick respiratory secretions, and additional oxygen may be required.
Reviewed by Dr John D. Burgess, FCPaed (CMSA), Senior Specialist, Red Cross Children's Hospital.