Croup or bronchiolitis

Victorian statutory requirement

Notification and school exclusion are not required.

Infectious agent

Respiratory syncytial virus (RSV), parainfluenza viruses and adenoviruses are the causative agents.

Parainfluenza type 1 virus is the most common cause of croup and RSV the most common cause of bronchiolitis.

Identification

Clinical features
Disease is generally characterised by fever and one or more systemic reactions such as chills, headaches, generalised aches, malaise and anorexia. Gastrointestinal disturbances may also occur. In babies and young children general features are often not apparent and disease presents with localising signs at various sites in the respiratory tract.

Croup
Croup (laryngotracheobronchitis) has a prodrome of fever, runny nose and sore throat. Cough is also common. Inflammation at the subglottic level produces a classic high-pitched inspiratory stridor and a hoarse voice. The larger airways are narrowed by inflammation resulting in various degrees of shortness of breath and increased respiratory rate. Airway obstruction can progress with in-drawing of the intercostal spaces and the soft tissues of the neck, cyanosis and death without urgent treatment.

Bronchiolitis
A one to seven day prodrome of mild fever, coryza and cough is common with bronchiolitis. Disease can rapidly progress to deepening cough, tachypnoea, restlessness, chest wall retraction, nasal flaring and grunting. Audible wheezing is a characteristic feature. It can be accompanied by paroxysms of coughing, vomiting, dehydration, otitis media and diarrhoea.

Method of diagnosis
The diagnosis of croup and bronchiolitis is usually based on characteristic clinical findings. Serologic diagnosis can be unreliable. Identification of the specific viral agent may be accomplished by isolation in tissue culture from throat, tracheal and nasal wash specimens, or by multiplex PCR.

Incubation period

The incubation period varies from one to ten days.

Public health significance & occurrence

There is limited data on the epidemiology of croup and bronchiolitis in Australia. Croup is more common in autumn and affects children aged three months to three years. It peaks in the second year of life. Bronchiolitis is more common in winter and predominantly affects children in the first year of life.

Lower respiratory tract infections due to viral agents are significant causes of infant and childhood morbidity and mortality worldwide. Persons with underlying cardiac or pulmonary disease or compromised immune systems are at increased risk for serious complications of RSV infection, such as pneumonia and death. RSV infection among recipients of bone marrow transplants has resulted in high mortality rates. Symptomatic RSV disease can recur throughout life because of limited protective immunity induced by natural infection.

Reservoir

Humans.

Mode of transmission

RSV is transmitted via oral contact, droplet spread or by contact with hands or fomites soiled by respiratory discharges from an infected person.

Period of communicability

RSV is communicable shortly prior to and for the duration of active disease. Prolonged shedding of RSV has been documented.

Susceptibility & resistance

Everyone is susceptible to infection. Reinfection with the agents that cause croup is common but the infection is generally milder.

Control measures

Preventive measures
There is no vaccine available. Basic hygiene can help limit the spread of many diseases including croup and bronchiolitis.

Control of case
Children with these diseases should not attend school or child care centres while unwell. Investigations are generally not indicated but may be useful in outbreak situations.

Control of contacts
Investigation of contacts is not necessary but the diagnosis in other family or close contacts should be considered if they are symptomatic.

Control of environment
Not applicable.

Outbreak measures

Public health action is dependant on the setting in which the case has occurred and is based on an assessment of ongoing risk. The risk for nosocomial transmission of RSV increases during community outbreaks. Nosocomial outbreaks of RSV can be controlled by adhering to contact and respiratory precautions.

Additional sources of information

Centers for Disease Control and Prevention, Atlanta USA, Respiratory syncytial virus infection
www.cdc.gov/ncidod

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