Overview
Pertussis, commonly known as whooping cough, is a highly contagious respiratory disease. It causes severe bouts of coughing, which may be accompanied by vomiting and a whooping sound.
In November 2024, health agencies confirmed that Aotearoa New Zealand is now in the early stages of a whooping cough epidemic, with a nationally coordinated response in place. It is expected NZ will see a rise in pertussis cases over the next 1-2 years.
Introduction
Pertussis can last up to three months and is sometimes referred to as the ‘hundred day cough’. The symptoms are more obvious in children, as infants and adults are less likely to ‘whoop’.
Epidemics occur in New Zealand every three to five years and several thousand cases (mostly young children) are reported during each epidemic.
In older adolescents, adults and older people, pertussis often goes unrecognised and is under reported. Up to a third of adolescents and young adults with a persistent cough have evidence of recent pertussis infection.
Transmission
Pertussis is highly contagious and is spread by coughing and sneezing. The Bordetella pertussis bacterium infects around 90% of non-immune household contacts.
Infants under 6 months old whose mother did not have a whooping cough booster immunisation during pregnancy and who are too young to have completed their first three immunisations are most likely to catch whooping cough from their mother. Siblings, adolescents and adults in the household, and health care workers are also sources of infection for this age group. Schoolchildren and adolescents tend to be infected by another student or friend.
A person with whooping cough is likely to be infectious from the week before they start coughing to three weeks after the cough begins.
Symptoms
About 5-10 days (but sometimes up to 3 weeks) after catching whooping cough, the early symptoms start, including a runny nose, sneezing, slight fever and a mild irritating cough which lasts 1 to 2 weeks. This is the most infectious period. Babies in this phase can get apnoea (stopping breathing) attacks.
The later stage symptoms include spasms of coughing followed by a big breath in or high-pitched ‘whoop’ sound in children. Infants and adults generally do not have the characteristic 'whoop'. Infants and young children often appear very unwell, and may turn blue and vomit with coughing bouts.
The recovery stage may last for months. Although the cough eventually disappears after several weeks, coughing fits may recur whenever the patient suffers any later respiratory infection.
Treatment
There is no treatment for whooping cough. Antibiotics, such as erythromycin, can be prescribed during the early stages to reduce spread of the disease.
Supportive measures to ease coughing spasms include:
- Warm drinks may be soothing and help break the coughing spasm
- A humidifier in the bedroom may help (it must be cleaned every 2 or 3 days)
- Saline nose drops to help remove thick mucus
- Drink lots of clear fluids
- Avoid coughing triggers, such as cigarette smoke, perfumes or pollutants
Supportive treatment for infants less than 12 months of age is essential because they have the highest risk of developing complications with long term consequences. Infants may need to be hospitalised for oxygen treatment and have mucous removed from their nose and throat with suction. Sometimes they need to be given fluid directly into their bloodstream and liquid nutrition directly into their stomach.
Risks
Those most at risk of serious disease are infants under 12 months of age. Infants who do not receive on-time doses of pertussis-containing vaccine at the scheduled times of 6 weeks, 3 months, and 5 months are five times more likely to be hospitalised with pertussis than those babies who are vaccinated on time.
Around half the babies who catch pertussis before the age of 12 months require hospitalisation and 1 or 2 in 100 of those hospitalised die from pertussis infection. Severe coughing can temporarily stop the oxygen supply to the brain (hypoxia). In around 2 in 1,000 children pertussis leads to permanent brain damage, paralysis, deafness or blindness. Secondary infections such as pneumonia and ear infections can occur.
The disease is usually milder in adolescents and adults, consisting of a persistent cough similar to that found in other upper respiratory infections, although for some adults violent coughing will result in collapse, rib fracture or pneumonia. Both hospitalisations and deaths are likely to be under-estimated in adults.
Prevention
The best protection for infants is for their mother to be vaccinated during pregnancy followed by on-time immunisations for the infant at 6 weeks, 3 months, and 5 months. Children are further protected with booster vaccines at 4 years and 11 years of age.
When a pregnant woman is vaccinated against whooping cough her body develops high levels of antibodies (disease-specific protective proteins) which will pass through the placenta. This helps protect the newborn from severe whooping cough for the first few months of life, until the infant has had their own three doses of vaccine and can make their own longer-term protection. A booster dose of a whooping cough vaccine (Boostrix) is free for women from the second trimester of every pregnancy and recommended to be administered from 16 weeks, preferably during the second trimester, but at least two weeks before birth.
Breastfeeding does not provide direct effective protection against whooping cough.
It is also recommended that close family contacts of young infants, such as grandparents and fathers have a booster dose of pertussis vaccine (if it has been more than 5 years since their previous one) to reduce spread of the disease. Older siblings should be up-to-date with their immunisations.
Those who are also eligible for a free Boostrix vaccination include parents or primary caregivers of infants admitted to a Neonatal Intensive Care Unit or Specialist Care Baby Unit for more than 3 days and who had not been exposed to maternal whooping cough immunisation at least 14 days before birth.
Children with whooping cough are advised not to attend early childhood services, school or other public places for three weeks after they started coughing or five days after starting antibiotic medicine. Adults are advised not to attend work or public places for the same periods of time.
Close contacts of a person with whooping cough who attend early childhood services, are in contact with infants less than 12 months of age or pregnant women, or who are health care workers, can complete a course of antibiotic medicine to reduce their risk of developing the disease.
A whooping cough booster immunisation will not prevent the disease developing if there has been a recent exposure.
