EPIDEMIOLOGY OF SARS

1. EPIDEMIOLOGY
OF SARS
DR. MAHESWARI JAIKUMAR.
maheswarijaikumar2103@gmail.com

4. AGENT

7. SARS
• SARS is a communicable viral
disease, caused by a new strain
of coronavirus, which differs
considerably in genetic structure
from previously recognized
coronavirus.

8. • The most common symptoms in
patient progressing to SARS
include fever, malaise, chills,
headache, myalgia, dizziness,
cough, sore throat and running
nose.

9. • In some cases there is rapid
deterioration with low oxygen
saturation and acute respiratory
distress requiring ventilatory
support.
• It is capable of causing death in
as many as 10% cases.

10. • Chest X-ray findings typically
begin with a small, unilateral
patchy shadowing, and progress
over 1-2 days to become
bilateral and generalized, with
interstitial/confluent infiltration.

12. • Adult Respiratory Distress
Syndrome has been observed in
a number of patients in the end
stages.

13. INCUBATION PERIOD
2 to 7 days, commonly 3 to 5
days.

14. MODE OF TRANSMISSION
• The primary mode of
transmission appears to be
through direct or indirect contact
of mucous membranes of eyes,
nose, or mouth with respiratory
droplets or fomites.

15. • The use of aerosol-generating
procedures (endotracheal
intubation, bronchoscopy,
nebulization treatment) in
hospitals may amplify the
transmission of SARS
coronavirus.

16. • The virus is shed in stools but the
role of faecal-oral transmission is
unknown.
• The natural reservoir appears to be
the horseshoe bat (which eats and
drops fruits ingested by civets, the
earlier presumed reservoir and a
likely amplifying host)

17. • The SARS virus can survive for
hours on common surfaces
outside the human body and
upto 4 days in human waste.

18. • The virus can survive at least for
24 hours on a plastic surface at
room temperature and can live
for extended periods in the cold.

19. CASE DEFINITION
• In the period following an
outbreak of SARS, a notifiable
case of SARS is defined as an
individual with laboratory
confirmation infection with SARS
coronavirus (SARS-CoV)….cont

20. ……..cont
• Who either fulfils the clinical
case definition of SARS or has
worked in a laboratory handling
live SARS-CoV or storing clinical
specimens infected with SARS-
CoV.

21. CLINICAL CASE DEFINITION
• A history of fever or documented
fever AND
• One or more symptoms of lower
respiratory tract illness(cough,
difficulty in breathing, shortness
of breath) AND…cont

22. Cont…
• Radiographic evidence of lung
infiltrates consistent with
pneumonia or acute ARDS or
autopsy findings consistent with
the pathology of pneumonia or
ARDS without an identifiable
cause AND…..cont..

23. Cont…
• No alternative diagnosis fully
explaining the illness.

25. DIAGNOSIS-1
• Conventional reverse transcriptase
PCR (RT-PCR) and real time reverse
transcriptase PCR (real time RT-
PCR) assay detecting viral RNA
present in : …cont

26. Cont..
• Atleast 2 different clinical
specimens (nasopharyngeal and
stool specimens).

27. • The same clinical specimen
collected on 2 or more occasions
during the course of the illness
(sequential nasopgarygeal
aspirates)…OR…cont…

28. Cont…
• A new extract from the original
clinical sample tested positive by
2 different assays or repeat RT-
PCT or real-time RT-PCR on each
occasion of testing OR..cont…

29. Cont…
• Virus culture from any clinical
specimen.

30. DIAGNOSIS-2
• Enzyme Linked immunosorbant
assay (ELISA) and
immunofluorescent assay(IFA)…
as follows,,

31. • Negative antibody test on serum
collected during the acute phase
of illness, followed by positive
antibody test on convalescent-
phase serum tested
simultaneously OR..cont..

32. Cont…
• A fourfold or greater rise in
antibody titre against SARS-CoV
between an acute phase serum
specimen and a convalescent-
phase serum specimen (paired
sera) tested simultaneously.

33. • In the absence of known SARS-
CoV transmission to humans,
the positive predictive value of a
SARS-CoV diagnostic test is
extremely low; ….cont..

34. Cont…
• Therefore, the diagnosis should
be independently verified in one
or more WHO international SARS
reference and verification
network labs.

35. • Every single case of SARS should
be reported to WHO.

36. EPIDEMIOLOGICAL ASPECT
• Health Care Workers, especially
those involved in procedure
generating aerosols, accounted
for 21 % of all cases.

37. • Maximum virus excretion from
the respiratory tract occurs on
about day 10 of illness & then
declines.

38. • The efficiency of transmission
appears to be the greatest
following exposure to severely ill
patients or those experiencing
rapid clinical deterioration,
usually during the second week
of illness.

39. • Children are rarely affected by
SARS.
• International flights have been
associated with the transmission
of SARS from symptomatic
probable cases to passengers or
crew.

40. • WHO recommends exit
screening and other measures to
reduce opportunities for further
international spread associated
with air travel during the
epidemic period.

41. COMPLICATIONS
• As with any viral pneumonia,
pulmonary decompensation is
the most feared problem.

42. • Patients often require intubation
which may results in sequelae
such as; intensive care ..
Infection from nosocomial
pathogens, tension
pneumothorax from ventillation
at high peak pressures & non
cardiogenic pulmonary oedema.

43. TREATMENT
• Sever cases require intensive
support.
• Ribavirin, Lopinavir, Ritonavir and
systemic corticosteroids were used
to treat SARS during 2003 epidemic.
(The efficacy of these drugs remains
inconclusive) and research is
needed.

44. PROGNOSIS
• The overall mortality rate of
identified cases is about 14%.
• Mortality is age related.

45. • Poor prognostic factors include
advanced age, chronic hepatitis B,
Diabetes Mellitus, Acute Kidney
disease, low counts of CD4 and
CD8.

46. PREVENTION
• No vaccine is available.
• Therefore preventive measures
against SARS include the
following.

48. • Prompt identification of persons
with SARS, their movements and
contacts.
• Effective isolation of SARS
patients in the hospitals.

49. • Appropriate protection of
medical staff treating these
patients.
• Comprehensive identification
and isolation of suspected SARS
cases.

51. • Simple hygienic measures such
as hand washing after touching
the patients , use of well fitted
masks and introduction of
infection control measures.

53. • Exit screening of international
travellers.
• Timely and accurate reporting
and sharing of information with
other authorities and/ or
governments.

54. THANK YOU