Pertussis (whooping cough)

Notification requirement for pertussis

Pertussis (whooping cough) is a 'routine' notifiable condition and must be notified by medical practitioners and pathology services to the Department of Health in writing within 5 days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centres exclusions

Children with pertussis (whooping cough) must not go to primary school and children’s service centres for 21 days after the onset of cough, or until they have received 5 days of appropriate antibiotic treatment.

Unimmunised contacts aged less than 7 years old in the same room as the case must not go to primary school and children's services centres for 14 days from the last exposure to infection, or until they have received 5 days of appropriate antibiotic treatment. For more information visit the School exclusion table page.

Infectious agent of pertussis

Pertussis is caused by infection with Bordetella pertussis bacteria.

Identification of pertussis

Clinical features

Pertussis causes a respiratory illness that can vary by age. Bordetella pertussis can adhere to the cells of the respiratory tract and release toxins that cause local tissue damage which are thought to contribute to cough symptoms by disrupting mucus clearance.

The initial catarrhal stage has symptoms of coryza, cough, tiredness and sometimes a low-grade fever. These symptoms may be indistinguishable from those of a viral upper respiratory tract infection.

The subsequent paroxysmal stage usually develops after 1 to 2 weeks of illness onset and is characterised by paroxysmal coughing (intermittent, rapid coughing fits). These occur particularly at night and may end in vomiting (post-tussive vomiting), cyanosis or a long inspiratory effort with a high-pitched ‘whoop’.

Infants aged less than 6 months and adults may not have the classical inspiratory ‘whoop'.

During the convalescent stage, cough symptoms gradually improve over several weeks. However, they may recur with subsequent respiratory tract infections for several months.

Complications

Complications from pertussis may include pneumonia, apnoea, seizures and encephalopathy which can be potentially fatal. Infants under 6 months of age are at highest risk of these complications and death.

Other complications may include dehydration from repeated vomiting, otitis media, epistaxis as well as hernias, prolapses, pneumothorax and rib fractures from strenuous coughing.

Diagnosis

Pertussis diagnosis is suspected based on clinical assessment and confirmed on laboratory tests. Early diagnosis in people with compatible illness is important and treatment should be commenced without delay in suspected cases.

Recommended laboratory testing for pertussis

This includes:

• NAT/PCR of nasopharyngeal swab or aspirate, which are the preferred diagnostic test for pertussis in all ages
• Serology of blood samples, which is only useful in some situations for people aged 2 years and older

Preferred diagnostic tests for age group

Nucleic acid tests (NAT), such as Polymerase chain reaction (PCR) tests, are the preferred diagnostic tests for pertussis in all ages. It is most sensitive in the first 3 weeks of illness and may be positive for up to 4 to 5 weeks after onset of illness.

Sampling collections and serology

Samples for NAT/PCR should be collected using Dacron™ or rayon tipped swabs, not calcium alginate swabs, and sent to the laboratory dry - not in transport medium.

Serology provides suggestive evidence of infection when there is compatible clinical illness and no history of recent pertussis vaccination. It is not recommended in children aged less than 2 years.

Both acute and convalescent samples should be collected. Interpretation of serology results can be difficult as detections can occur after vaccination (possibly up to 2 years) or in people with past infection, or it may be falsely negative in early illness.

Testing

Testing of pertussis cases contacts, who are less than 6 months old is particularly important to limit potential transmission. Infants who appear well, but with a history of cough, choking, gasping and difficulty catching breath should also be reviewed for pertussis.

Incubation period of Bordetella pertussis

The incubation period ranges between 4 to 21 days with symptoms usually occurring within 7 to 10 days after exposure.

Reservoir for Bordetella pertussis

Humans are the only known natural reservoir of Bordetella pertussis.

Mode of transmission of Bordetella pertussis

Bordetella pertussis is highly infectious. Person-to-person transmission mainly occurs through respiratory droplets and direct contact with respiratory secretions from an infected person.

Transmission can also occur less commonly through contact with contaminated objects and surfaces.

Secondary attack rates of 80 per cent have been reported among susceptible household contacts. Adults, adolescents and older children are often the source of infection in infants.

Period of communicability of pertussis

People with pertussis are considered infectious from the onset of catarrhal symptoms until 21 days after the onset of cough, or until they have received 5 days of appropriate antibiotic treatment.

Susceptibility and resistance to pertussis

Pertussis can affect people of all ages. However, young infants are at increased risk of infection, hospitalisation and death.

Protection from vaccination and previous infection wanes over time over 6 to 10 years.

Groups at increased risk of pertussis include:

• young infants under 6 months of age
• people who have not been vaccinated against pertussis
• people who have not received a pertussis booster in the past 10 years
• people living in the same house as someone with pertussis.

Public health significance and occurrence of pertussis

Pertussis (whooping cough) is a highly infectious respiratory illness caused by bacterial infection that disproportionately impacts young infants. Hospitalisation and mortality rates from pertussis are highest in infants aged under 1 year. However, deaths due to pertussis are now uncommon in Australia.

In Australia, there is a seasonal pattern with most cases notified during spring and summer. Epidemics of pertussis occur intermittently about every 3 to 4 years.

In 2015, more than 20,000 cases were notified nationally. Under one-quarter (or approximately 4,600 cases) of these occurred in Victoria and around one third of these Victorian cases occurred in children aged under 15 years.

Case numbers subsequently declined and were beginning to rise again in 2019 until the onset of the COVID-19 pandemic in 2020 when case numbers declined again. There were under 300 notified cases in Victoria in 2022.

Globally, between approximately 116,000 to 250,000 cases of pertussis were reported each year in the 20 years preceding the COVID-19 pandemic in 2020. Case numbers from 2022 show an increasing trend again.

The source of infection in infants is often from older children, adolescents and adults. As protection from pertussis vaccination, as well as natural immunity, wanes over time it is important to stay up to date with recommended vaccinations.

Current public health interventions are primarily focused on protecting young infants who are at increased risk of morbidity and mortality.

Control measures for pertussis

Preventive measures

Vaccination is the most important preventive measure against pertussis as it reduces the risk of infection and severe illness.

However, protection is incomplete and wanes over time. Therefore, people are recommended to stay up-to-date with their vaccinations, including booster doses, and seek medical attention early if symptoms of pertussis occur.

In Australia, pertussis vaccine is only available in combination with other antigens such as diphtheria and tetanus. Combination vaccines may also include inactivated poliovirus, hepatitis B and Haemophilus influenzae type b.

Free pertussis-containing vaccination is provided to eligible people through the National Immunisation Program schedule which include:

• infants at 2 (can be given from 6 weeks of age), 4 and 6 months of age
• children at 18 months and 4 years of age
• adolescents at 12 to 13 years of age (Year 7 or age equivalent)
• pregnant women in every pregnancy between 20 to 32 weeks gestation
• people under 20 years if the vaccine was not given during childhood as catch-up vaccination.

Check the immunisation status of all children and catch-up any missed doses.

Pregnant women

Pregnant women are recommended to receive a pertussis-containing vaccine in every pregnancy ideally between 20 to 32 weeks gestation. Vaccination during pregnancy reduces the risk of pertussis in young infants by 90 per cent.

Adult vaccination

Pertussis vaccination is recommended for any adult who wants to protect themselves from becoming ill with pertussis. People not eligible to get a funded vaccine can obtain the pertussis-containing vaccine through private prescription from their doctor or immunisation provider.

An adult pertussis-containing vaccine is also recommended for the following groups, regardless of their diphtheria, tetanus or pertussis vaccination history:

• Adults working with or caring for children, especially healthcare and childcare workers in contact with infants.
• Partners of pregnant women in the third trimester if they have not received a pertussis-containing vaccine in the past 10 years.
• Parents or guardians of infants, if their infant is under 6 months of age, and they have not received a pertussis-containing vaccine in the past 10 years.
• Adults 65 years of age and older if they have not received a pertussis-containing vaccine in the past 10 years, offered as a single booster.

For further guidance on pertussis vaccination refer to the Australian Immunisation Handbook – Pertussis (whooping cough).

Control of case

Early diagnosis and treatment are important to prevent onward transmission.

Antibiotic treatment reduces the infectious period and should be given as soon as possible within 21 days of cough onset. It should also be given for pneumonia complications. However, there is no established evidence that antibiotic treatment alters the clinical course of illness.

For further guidance on antibiotic treatment refer to the latest edition of the Therapeutic Guidelines and the Royal Children’s Hospital Melbourne Clinical Practice Guidelines.

In hospital settings, patients with pertussis should be cared for under droplet precautions in a single room while infectious.

People with pertussis should be excluded from work and avoid contact with infants and women in the last month of pregnancy while infectious. This is until 21 days after the onset of cough, or until they have received 5 days of appropriate antibiotic treatment, when they are no longer considered [missing word?]

Control of contacts

Close contacts include:

• family and household members
• people who stayed overnight in the same room as the case
• people who have had face-to-face contact (within 1 metre) to an infectious case for at least 1 hour.

Close contacts are informed of their exposure to pertussis and advised to monitor for symptoms. If symptoms develop, they should seek medical care early.

Prophylactic antibiotics are recommended for high-risk close contacts to reduce the risk of transmission to infants and people who may transmit infection to them.

Household settings: High-risk contacts

For exposures in household settings, high-risk contacts include:

• infants aged less than 6 months
• expectant parents (or carers) in the last month of pregnancy
• household members where there is an infant aged less than 6 months.

Healthcare and childcare setting: High-risk contacts

For exposures in healthcare and childcare settings, high-risk contacts include:

• infants aged less than 6 months
• women in their last month of pregnancy
• healthcare staff working in a maternity ward or newborn nursery
• childcare staff who look after infants aged less than 6 months
• children in childcare who have close contact with infants aged less than 6 months.

Prophylactic antibiotics are only effective if given as soon as possible within 14 days of first exposure to an infectious case. There is little evidence that antibiotic prophylaxis reduces secondary transmission outside of these high-risk contacts.

For further guidance on antibiotic prophylaxis refer to the latest edition of the Therapeutic Guidelines and the Royal Children’s Hospital Melbourne Clinical Practice Guidelines.

Primary school and children’s education centres exclusions apply for unimmunised close contacts aged less than 7 years old in the same room. The case must be excluded for 14 days from the last exposure to pertussis, or until they have received 5 days of appropriate antibiotic treatment.

Control of environment

Not applicable.

Outbreak measures for pertussis

Epidemics of pertussis occurs every 3 to 4 years in Australia. Prevention measures focus on immunisation and education.

Outbreaks can occur sporadically and are managed by the Local Public Health Unit.