RSV is a common virus that usually causes mild upper respiratory tract infections but can sometimes lead to pneumonia or bronchiolitis in young children. It is transmitted through respiratory secretions and contaminated surfaces. While infection leads to immunity against that RSV subtype, reinfection is still possible. Diagnosis involves antigen detection, viral culture, or PCR from respiratory samples. Treatment is supportive, though ribavirin may help severe cases. Development of an effective vaccine remains an ongoing effort.

1. Respiratory Syncytial
Virus (RSV)

2. Classification
• Family: Paramyxoviridae
• Sub-family: Pneumovirinae
• Genus: Pneumovirus

3. Morphology
• irregular spherical particles that
range in diameter from 150 to 300
nm
• consists of a nucleocapsid contained
within a lipid envelope
• non-segmented, single-stranded,
negative-sense genome of helical
symmetry

4. • has four nucleocapsid proteins
packaged in the virion: the major
nucleocapsid protein N, the
phosphoprotein P, the antitermination
factor M2-1, and the large
polymerase subunit L.
• envelope contains three virally
encoded transmembrane surface
glycoproteins, the attachment
protein G, the fusion protein F, and
the small hydrophobic SH protein

5. • The viral glycoproteins are organized
separately into virion “spikes,” which
are visualized as short (11–20 nm),
closely spaced (intervals of 6 to 10
nm) surface projections
• There also is a matrix M protein that
is thought to form a layer on the
inner envelope face

6. • RNA genome is 15-16 kb long
• Genome encodes 11 proteins
• Nine are structural (L, G, F, N, P, M,
M2-1, M2-2 and SH)
• Two are non-structural (NS1 and
NS2)
[RSV is divided into two antigenic
subgroups (A and B) on the basis of G
surface glycoprotein]

8. Epidemiology
• RSV infection is prevalent worldwide
• Highly contagious in nature
• Highly prevalent in young children
with a peak incidence in 2-8 months
of age
• Virtually all children are infected by
RSV by the age of 4 years.
• Usually seasonal, mostly occuring
during winter

9. • Shed in respiratory secretions for
several days, sometimes weeks
• Nosocomial infections are frequent.
• Outbreaks occur in neonatal wards of
maternity hospitals, sometimes
inflicting high mortality

10. Replication
• All events in the RSV replicative
cycle occur in the cytoplasm without
nuclear involvement
• Attachment is mediated by G
glycoprotein with specific cellular
receptor (suggested to be cellular
GAGs, “glycosaminoglycans”)
• Replication is similar to that of
Paramyxoviruses

11. Transmission
• Droplet inhalation
• Direct contact with contaminated
hands and fomites

12. Pathogenesis
• RSV is restricted to the respiratory
tract
• Inoculation of the virus occurs
through the upper respiratory tract
and initiates infection in the
epithelial cells.
• The virus subsequently spreads along
the epithelium of the respiratory
tract, mostly by cell-to-cell transfer
of the virus along intracytoplasmic
bridges (or syncytia formation).

13. • The virus usually does not cause any
viremia or systemic spread.
• As the virus spreads to the lower
respiratory tract it may produce
bronchiolitis and/or pneumonia.
• Virus causes necrosis of the small
airway epithelium, plugging of the
lumens with exudates, and edema,
leading to obstruction of the normal
airways.

14. Immune response
• Antibodies of IgA, IgM and IgG
classes are produced but plays the
minimal role in the host immunity
against RSV.
• Systemic and local cell-mediated
immune responses appear to be key
to the severity and recovery from
RSV infection
• Reinfection occurs, but of low
severity than that of primary
infection

15. • Maternal antibody does not protect
infant from infection.
• Natural infection does not prevent
reinfection
• Improper vaccination increases
severity of disease

16. Clinical manifestations
• The incubation period from time of
infection to onset of illness for RSV
is 4 to 5 days
• In the normal infant who encounters
RSV for the first time at age 6
weeks to 9 months, RSV infection
usually causes upper respiratory
symptoms.

17. • In 25% to 40% of such infections,
however, the respiratory tract below
the larynx also becomes involved.
• Bronchiolitis and pneumonia are the
primary manifestations of lower
respiratory tract disease
• RSV has been reported in various
studies as causing 10% of croup
cases, 5–40% of the pneumonias and
bronchitis in young children, and 50–

18. • Clinically, the condition presents as
cough, coryza, wheezing, rales and
low-grade fever.
• Reinfection with the virus occurs
throughout the life.
• However, in advancing age, the RSV
infection is confined more to the
URT than the LRT.

19. Complications
• Secondary bacterial complications are
rare.
• Approximately 20% of children with RSV
bronchiolitis develop a viral otitis media.
• Small children with bronchiolitis during
their first year of life may develop
chronic respiratory disease, in particular
asthma.

20. Laboratory diagnosis
• RSV infection may be diagnosed by
identification of the viral antigen by
rapid diagnostic techniques, viral
isolation or serology
• The gold standard is isolation of
virus in cell culture
• Specimens are best obtained by
aspiration or gentle washing out of
nasal or nasopharyngeal secretions or
by nasal swab

21. • Rapid antigen detection
• Viral antigens can be detected by direct
immunofluorescence or enzyme immunoassy
using specific monoclonal antibodies.
• Virus culture
– HeLa cells, Hep-2 cells or monkey kidney
cell lines can be used
– After 3-10 days of inoculation and
incubation, RSV is identified by the
characteristic synsytium formation
– DFA test can be employed for viral
detection in earlier days

22. • Serodiagnosis
– ELISA can be used for the
demonstration of antibodies in the
serum
– Demonstration of fourfold or more
increase in the antibody titer of acute
and convalescent sera
• Molecular diagnosis
– PCR

23. Prophylaxis and control
• Supportive and symptomatic care
• Ribavirin has been recommended for the
aerosolized treatment of childern with
severe RSV disease.
• Parenterally administration of RSV-
neutralizing antibodies is suggested as an
antiviral therapy against established
infection of high-risk infants and young
children.

24. • Development of effective vaccine
against RSV have not succceed to
date.