Croup:
Croup, or acute
laryngotracheobronchitis, is the most common infectious cause of sudden upper
airway obstruction in children and of stridor in febrile children. Croup accounts for more than 15% of
pediatric respiratory illnesses.Children aged 6 months to 6 years--especially
boys--are affected most often: the peak incidence occurs during the second year
of life. About 2% of all preschoolers have croup every year, and recurrence is
common. Croup can develop at any time of the year, although it classically
presents in late autumn and winter.
Although croup can be caused by bacteria (eg, Staphylococcus
aureus, Haemophilus influenzae,
Corynebacterium diphtheriae, and Mycoplasma pneumoniae) and atypical agents,
most cases are viral. The leading cause of croup, isolated from more than 80%
of positive cultures, is parainfluenza virus (types 1, 2, and 3). Other viruses that can cause croup
include adenovirus, influenza A and B viruses, respiratory syncytial virus
(RSV), and rubeola virus.
The time and manner in which the child presents may yield general
clues to the cause of the viral croup. For example, parainfluenza viruses predominate
in the fall, whereas RSV croup peaks in the midwinter. The most severe illness
is caused by influenza A virus infection.
Bronchiolitis:
Bronchiolitis is one of
the most common and serious viral infections to affect the small and medium
airways of the lower respiratory tract in young children.Almost 85% of all
reported cases of bronchiolitis are caused by RSV. However, parainfluenza virus,
adenovirus, influenza A virus, and rhinovirus can also be responsible.
Bronchiolitis targets young children, particularly those aged 2 to 6 months.
Most children are infected by age 3; roughly 10% have clinically
diagnosed
bronchiolitis during the first year of life. Bronchiolitis is a seasonal
illness: the peak incidence occurs in winter and early spring.
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 reactionssuch as chills, headaches, generalized aches, malaise and
anorexia. Gastrointestinal disturbances may also occur. In babies and young
children general features are often not apparent and disease presents with localizing
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 and 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 and 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.
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,
·
The blue book: Guidelines
for the control of infectious diseases
0 comments:
Post a Comment