Swine influenza primarily affects the respiratory system and is contagious through respiratory droplets or contact with infected surfaces. It is characterized by antigenic drift, necessitating annual vaccination and early clinical diagnosis for effective treatment. Complications can range from mild to severe, emphasizing the importance of timely antiviral intervention and infection control measures, especially during peak influenza seasons.

1. Swine
Influenza
DR. HIMIL PARIKH
FIRST YEAR RESIDENT
PATHOLOGY DEPARTMENT

2. Overview
 Affects respiratory tracts (Contagious)-
Sick to susceptible persons through close
contacts
 Transmitted: 1. Respiratory droplets in coughing
2. Touching virus infected material
and then touching eyes, mouth or
nose

3. Antigenic drift
 Influenza A and B  Gradual changes in antigenic
composition (antigenic drift)  New viral strains 
Reason for surveillance of strains of influeza viruses and
why each year these vaccine strains are updated
 CDC  6 months and older  vaccination every year
unless contraindicated
 Early diagnosis  early treatment  decreased severity
of illness, hospitalization and hospital stay
 Testing every patient with S/S of influenza is not cost
effective and hence diagnosis should be made clinically
as far as possible (Antivirals only if they change the
clinical course)

4. Epidemiology
 Influenza epidemics occur during winter, can occur as
early as october and peaking in Jan or later
 More temperate region influenza activity in April to
sept
 Tropical regions Throughout the year and peaks in
rainy and dry seasons
 Trvelers can be exposed outside ‘typical’ influenza
season

5. Influenza transmission
 One day prior to onset  potentially infectious
 Upto 5 days after onset  contagious
 Within 4 days  most transmissions occur
 Young children/ Immunocompromised contagious for
longer period of time
 Person to person respi droplets to susceptible
person within 6 ft distance
 Health care personnel can spread influenza to patients
in their care
 Transmissions like these increase morbidity, mortality
and cost… Hence, infection prevention is CRITICAL

6. Surveillance awareness
 Influenza viruses change constantly
 New or different strains may be identified each year
 You need to be aware of actively circulating strains of
influenza and antiviral susceptibility for accurate
diagnosis and treatment decisions are made
 Visit cdc weekly

7. The Influenza Challenge
 Spectrum of clinical presentation
 Person-person difference and includes other factors-
. Age
. Underlying conditions
. Immune status of an individual
 Many other respi. Illnesses present similar s/s – making
Dx even more challenging
1. Respi syncytial virus
2. Rhinovirus
3. Parainfluenza virus
4. Adenoviruses and others which circulate around during
influenza season

8. Clinical Features
Vomiting or diarrhea (not typical for influenza but reported by recent c
ases of swine influenza infection)

9. Other Manifestations
• Tachycardia
• Tachypnoea
• Low O2 saturation
• Hypotension
• Cyanosis
• Acute myocarditis
• Cardiopulmonary arrest

11. High activity of influenza
 Consider diagnosis in the following types of patients regardless
of vaccination status
1. immunocompetent/compromised with fever and acute onset of
repiratory s/s
2. Fever and acute exacerbation of underlying chronic lung
disease
3. Infants and young children with fever and no other s/s
4. Elderly with new or worsening respi symptoms including
exacerbation of CHF or alterred mental status with without
fever
5. Anyone severly ill with fever or hypothermia
6. Adults or children hospitalized without fever and acute respi
symptoms who then subsequently develop fever (children-only)
or febrile repi illness after admission (IDSA guidelines)

12. Low activity
 During any time of the year consider diagnosis in
following types of patients-
 Immunocompetent/compromised pt with acute febrile
respi symptom, epidemiologically linked to an influenza
outbreak
 Returned travelers from countries where influenza
viruses may be circulating

13. High Risk
 < 5 yrs (especially <2 yrs)
 >/= 65 years
 Pregnant
 Chronic medical conditions
 Native americans/alaskan naatives

14. Complications
 Mild: Otitis media, Sinusitis
 Severe: Exacerbation of underlying medical conditions,
pneumonia, secondary invasive bacterial infection; RARE-
Encephalopathy, Encephalitis, Myositis, Rhabdomyolysis,
Myocarditis and death.
 In US- 3000 to 49000 deaths (90% consist of >65 years of
(death))- CDC report
 Billions of dollars cost to US
 Annual vaccination – only effective measure against
influenza

15. Case
 Pregnant woman hospitalized for pneumonia in a general
medical ward during the Pandemic wave
 Clinicians dismissed diagnosis of influenza as pt tested
negative on ridt for nasal swab (influenza A) – treatment
started – broad spectrum ab and antifungal agents after
describing an unusual pneumonia on chest ct scan-
patient’s respiratory condition continued to deteriorate
until 5 days after admission when she went into
respiratory failure when she was intubated and placed on
mechanical ventilation in an ICU- Endotracheal aspirate
tested positive for 2009 H1N1 by Real time RT-PCR –
antiviral Rx started very late in the clinical course in ICU

16.  Demonstrates several points-
1. Sensitivity of RIDT in diagnosing influenza A is low to
moderate and many false negative results occur
2. Studies suggest benefit of antiviral agents in Influenza
is greatest if started early (especially those at high
risk)
3. Proper interpretation of influenza testing result (If test
result is negative and still S/S suggestive of influenza
 start antivirals empirically + additional influenza
testing to be done

17. Influenza testing
 Not required in all
 Done only if result influences management in
decisions
• Initiation of antiviral Rx
• Impact on other diagnostic testing
• Antibiotic testing
• Infection control practices
 Remain aware about sensitivity and specificity of test
type (also local influenza activity information)

18. 1- COMPLETE HEMOGRAM: Leucopenia, thrombocytopenia and
anemia.
2- LIVER FUNCTION TEST:- Raised liver enzymes and elevated
bilirubin.
3- OTHERS: Increased CPK and LDH.
4- X-RAY: Bilateral infiltrates(lower lobe predominance).
5- CT CHEST: Patchy consolidation or ground glass opacities.
NON SPECIFIC
FINDINGS:

19. Testing guide
Does the patient have clinical signs and
symptoms compatible with influenza?
YES
NO
Will the results of influenza virus testing:
• Change clinical care of the patient
-OR-
•Influence the clinical practice for other patients?
Initiation of antiviral treatment, if clinically indicated,
*should not be delayed pending results of testing.
Influenza virus testing
probably not indicated
Consider influenza virus testing
(Visit Resources section to see the different types of
influenza virus testing methods)
Influenza virus testing
probably not indicated
YES
NO

20. Diagnostic Test Overview
Influenza Diagnostic
Tests
Viral Culture
Rapid Cell Culture
Immunofluorescence
RT-PCR
Rapid Influenza Diagnostic
Tests (RIDTs)
All of them vary in:
• Availability
• Performance
• Ease
• Timeliness
• Equipment
• Reagent costs
Most require sophisticated laboratory
capacity and highly skilled laboratory
staff- with exception of Rapid Influenza
Diagnostic Tests (RIDTs).
Currently, the only test performed and
interpreted with:
• Results in less than 30 minutes
• No specialized equipment
• Great for point-of-care- physician’s
offices or clinics without laboratory
services, or in remote settings.

21. Testing in Ambulatory
Settings:
Common types used:
 Rapid Influenza Diagnostic tests (RIDTs)
 Immunofluorescence
(Updated 9/2016) Molecular assays for influenza are increasingly being used in
clinical settings and may be available in outpatient settings. Rapid molecular
assays are a new type of molecular influenza diagnostic test that can
provide results in approximately 20 minutes.
Two FDA-cleared influenza rapid molecular assays available in the US:
1. Alere I influenza A & B for nasal swabs (direct) or nasal swabs in VTM.
2. Roche Cobas influenza A/B (for nasopharyngeal swabs only)

22. RIDT
 Immunoassays that can identify the presence of
influenza A and B viral nucleoprotein antigens in
respiratory specimens.
 Results: Displayed qualitatively as + or –
 Reported sensitivity of RIDT ranges between 40%
to 70%.
 The reported specificity of RIDT ranges from 90%
to 99%.

23. Immunofluorescence
 A test used to detect influenza antigens
 Requires:
• Specialized equipment i.e. fluorescent microscope
• Laboratory expertise
 Use:
1. With exception of the Emergency department, NOT used
in many outpatient situations
2. Specimens to be delivered to the laboratory for
processing
3. Once processing is complete, results become available
within HOURS

24. Before using RIDTs
 RIDTs may be used to help with diagnosis and treatment decisions,
particularly if performed within the first 3 days of onset of
symptoms.
 However, clinicians must consider the following before ordering a
rapid influenza diagnostic test:
o RIDTs have a higher sensitivity for detecting Influenza A
compared to Influenza B- knowledge of current circulation of
influenza strains is critical
o RIDTs perform better in children than in adults- 13% higher
sensitivity.
o RIDTs should be performed only if results influence the clinical
management of the patient.

25. Additional Considerations
Using RIDTs
ILI Activity level RIDT
Results
Patient
HIGH
MODERATE

26. Additional Considerations
Using RIDTs
ILI Activity level RIDT
Results
Patient
HIGH
MODERATE

27. Additional Considerations
Using RIDTs
Antiviral Treatment
Treat Treat

28. Influenza Virus Isolates
 Rapid tests do not address the public health need for influenza
virus isolates; viral cultures are required.
 Virus isolates are essential for:
 Determining the match between circulating influenza viruses and
those viruses contained in the vaccine.
 Aiding in the selection of new vaccine strains.

29. RIDT Advantages and
Disadvantages
Advantages Disadvantages
Simple to Perform Suboptimal test sensitivity – false
negative results are common when
influenza activity is high
Results in as little as 15 minutes Some distinguish between
influenza A or B viruses, while
others do not
Most distinguish between influenza
A and B virus infections
Those providing results on the
virus type do not provide
information about virus subtypes or
strains
May be performed in ambulatory
point of care settings
Cannot provide information
regarding antiviral drug
susceptibility

30. Influencing Factors
 For proper sample collections: Strictly follow package instructions to
identify the type of acceptable specimen
 The factors influencing RIDT results include:
1. Type and quality of the specimen.
2. Timing of the specimen collection during illness.
3. Prevalence of influenza activity in the community.

31. Type and quality of the
specimen
 RIDT kits have different specifications for acceptable specimens.
 Package insert:
Review to ensure:
 Appropriate specimen is collected.
 Test procedures are followed.
 Transport Media:
Viral transport media must be consistent with the test specifications-
especially when testing and collection are conducted in different
locations.
 Timing:
Testing should occur within appropriate window as indicated in the
manufacturer’s instructions for the type of kit being used.

32. Timing of the specimen
collection during illness
 The presence of clinical signs and symptoms increases the likelihood
that a positive test result is a true positive.
 Respiratory specimen collection
For an ill patient:
 Should be collected as soon as possible.
 Ideally less than 48-72 hours after onset of symptoms.
For young children:
 The virus can be shed for longer periods. Testing a few days after this
period may still be useful.

33. How to collect specimens?
The following videos show how to collect specimen
necessary for Swine influenza testing.

34. Nasopharyngeal Swab Procedure

35. Nasal Swab Procedure

36. Combination of Nasal and Throat swab

37. Pediatric nasal aspirate

38. Prevalence of influenza
activity in the community
 Influenza activity is seasonally variable.
 Directly affects predictive values of RIDTs.
 Variations in predictive values is due to the volume of positive cases
presented.
 False-negative (and True-positive) results more likely
when:
 Disease prevalence is HIGH (Typically at the height of the influenza
season)
 False-positive (and True-negative) results are more likely
when:
 Disease prevalence is low (Generally at the beginning and the end of the
influenza season)

39. Interpretation of RIDT
 Interpret results by considering circulating influenza
activity.
 When circulation and suspicion is HIGH- an RIDT doesn’t
need to be performed.
 If the results change the clinical care, a test may be
warranted.
 Due to the limited sensitivities of RIDTs, negative results
do not exclude influenza virus infection in patients with
signs and symptoms suggestive of influenza.

40. Timeframe for Results
 The package insert includes information on:
1. The proper time frame for the reading of results
• Most RIDT kits offer results in 10 to 30 minutes.
2. Storage of specimens without interference of
performance
• Some may be stored refrigerated or at room temperature.
• Be sure to use the proper viral transport medium.

41. Early antiviral treatment
 Clinical and observational data show that early
antiviral treatment:
• Can shorten the duration of fever and illness symptoms.
• Reduce the risk of complications from influenza, when
started within 48 hours of symptom onset.
A history of vaccination doesn’t rule out the possibility of a
virus infection in an ill patient with clinical signs and
symptoms compatible with influenza.

42. Antiviral Medications
Licensed Prescription Influenza Antiviral Agents
Amantadine (Symmetrel®) Rimantadine (Flumadine®)
Zanamavir (Relenza®) Oseltamivir (Tamiflu®)
FDA- approved influenza antiviral medications recommended during
influenza season.
Chemically related neuraminidase inhibitors with antiviral activity against
both influenza A and B viruses
Sporadic-resistant 2009 H1N1 virus infections have been identified.
Expect future cases

43. Antiviral Medications
Licensed Prescription Influenza Antiviral Agents
Amantadine (Symmetrel®) Rimantadine (Flumadine®)
Zanamavir (Relenza®) Oseltamivir (Tamiflu®)
Influenza A
viruses
Influenza B
viruses
Circulating
2009 H1N1
influenza
virus
Seasonal
Influenza A
(H3N2)
viruses

44. Antiviral Medications
Licensed Prescription Influenza Antiviral Agents
Amantadine (Symmetrel®) Rimantadine (Flumadine®)
Zanamavir (Relenza®) Oseltamivir (Tamiflu®)
Influenza A
viruses
Influenza B
viruses
Circulating
2009 H1N1
influenza
virus
Seasonal
Influenza A
(H3N2)
viruses

45. Antiviral treatment in
Adults
 The majority of persons infected with influenza virus exhibit
self limited, uncomplicated, acute febrile respiratory
symptoms.
 Those with underlying medical conditions, the very young,
and the very old are at a greater risk to develop serious
complications.
 Early antiviral treatment can reduce the risk of
complications from influenza.

46. Antiviral treatment for cases
• Duration of treatment: 5 days BD
• Dosage schedule
Weight Dosage
<15 kg 30 mg BD 5Days
15-23 kg 45 mg BD 5Days
24 to <40kg 60 mg BD 5Days
>40 kg 75 mg BD 5Days

47. Antiviral treatment for cases- Infants
• Duration of treatment: 5 days BD
• Available as oral suspension
• Dosage schedule
Months Dosage
<3 months 12mg BD 5Days
3-5 months 20mg BD 5Days
6-11 months 25mg BD 5Days

48. Other antiviral considerations
 Antiviral treatment may be considered for the following:
• Any previously healthy, symptomatic outpatient not at high risk with
confirmed or suspected influenza- if started <48 hours after onset of
symptoms.
• Do not wait for laboratory confirmation
• Vaccination history doesn’t rule out the possibility of an infection
when a patient presents consistent with signs and symptoms.
• Any otherwise healthy child with confirmed or suspected influenza, for
whom a decrease in duration of clinical symptoms is felt to be warranted by
his or her provider- if treatment can be initiated within 48 hours of illness
onset.

49. Antivirals for
chemoprophylaxis
Account for:
• The exposed person’s risk for complications.
• The type and duration of contact.
• Recommendations from local public health authorities.
Clinicians should also:
• Initiate within 48 hours of the most recent exposure.
• Continue for 7 days- but do not exceed 10 days.
• Consider patient compliance.

50. Antiviral dosage for
chemoprophylaxis
• Duration of treatment: 10 days OD
• Dosage schedule
Weight Dosage
<15 kg 30 mg OD 10 Days
15-23kg 45mg OD 10 Days
24to<40kg 60mg OD 10 Days
>40 kg 75mg OD 10 Days

51. Antiviral dosage for
chemoprophylaxis -infants
• Duration of treatment: 10 days OD
• Chemoprophylaxis not recommended for children below
3 months generally
• Dosage schedule
Months Dosage
3-5 months 20 mg OD 10 Days
6-11 months 25 mg OD 10 Days

52. Disinfectants
• 1% Sodium or Calcium hypochlorite solution
• 5% Lysol
• Surgical spirit with minimum of 70% alcohol

53. Personal Protection
When collecting a respiratory specimen, personal
protective equipment(PPE) should be worn all times:
• Lab coat
• Mask- surgical, dental, medical procedure, isolation
or laser mask
• Eye protection
• Gloves
Most point of care RIDT are simple:
• Insert a swab into medium
-OR-
• Pipette specimens and reagents
Since many do not generate aerosols, only splash
protection is required.

54. Hand Hygiene

55. Hand Hygiene

56. What should I do?
• First and most important: wash your hands
• Practice cough etiquette
• Get plenty of sleep
• Drink plenty of fluids
• Avoid touching surfaces that may be contaminated with
the flu virus.

57. What should I do?
• Avoid close contact with people who are sick.
• Staying at home if you have flu like symptoms
• Educating school children and staff, advising avoidance
of mass gatherings
• Avoid crowded places, avoid hand shaking

58. Thank You!