Transcript H1N1 Epidemiology, Clinical by Dr Sarma

www.drsarma.in
Dr. R V S N Sarma., MD., MSc. (Canada), FIMSA
Consultant Physician & Chest Specialist
• To compile this comprehensive presentation many resources on
the internet are reviewed and relevant material like text, pictures,
images, diagrams etc., are incorporated.
• The main objective is to share the wide knowledge, at this hour
of need, with all the physicians I come across and in turn help
the patients and the community at large.
• Scientific information from CDC, WHO, NIH, ECDC, BMJ, NEJM,
Flu watch, SEARO, MOHFW, NCDC (NICD) is invaluable.
• I record my sincere thanks and acknowledge using these
resources. The references are listed at the end.
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Essential – Positive – Constructive Approach
• Adequate awareness in general public – preventive measures
• Comprehensive knowledge for the healthcare providers
• Appropriate planning and responsibility of all involved
Unwarranted – Misleading – Dangerous – Negative reactions
• Fear, minute to minute monitoring of deaths, rumors
• Media hype, Anxiety about infection and death by this flu
• Panic, mania of mask use by one and all, and worry
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• Influenza A
– Common, More Severe, Several Sub-types
– Epidemics, Pandemics,  Mortality, High Mutagenicity
• Influenza B
– Less Severe, Less Frequent, No Sub types, Faithfully Human
• Influenza C
– Mild, Rare, No Sub types, Non fatal, Mild Illness in Children
• Common Cold – Coryza & Other Viruses – Not Flu
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Symptoms
Influenza
Common Cold
Fever
Usually high grade; 3-4 d
Unusual
Head ache
Yes
Unusual
Fatigue
May last up to 2-3 weeks
Mild
Myalgia
Usual and often severe
Slight
Exhaustion
Early and sometimes severe
Never
Stuffy nose
Sometimes
Common
Sore throat
Sometimes
Common
Cough
Yes
Unusual
Chest pain
Common / may be severe
Mild
Complications
Bronchitis, Viral or Bacterial pneumonia
Sinus congestion
Neuraminidase (N)
For Detachment
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Hemagglutinin (H)
for Attachment
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Orthomyxoviridae Family
Single stranded RNA virus
High mutagenicity, 8 proteins
H Ag types are 16
N Ag types are 09
So, 16 x 9 = 144 types possible
But only 3 types infect Humans
H1N1, H2N2 and H3N2
Avian Flu Virus is H5N1
Virus H1N1 - ‘Swine Flu’ Misnomer
Present Pandemic – (H1N1)v
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Orthomyxoviridae Family
Single Stranded RNA virus
High mutagenicity
Two viruses co-infect the same cell
New virus with segments of both
A mix of Avian, Swine and Human
This is genetic reassortment
Doesn’t require pigs as intermediary
‘Swine Flu’ is now named H1N1v
Present Pandemic – (H1N1)v
This is less virulent than H5N1
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Seasonal Epidemic Influenza
Pandemic Influenza H1N1
A public health problem each year
Rare and unpredictable in population
Some immunity from previous exposures
No herd immunity, Virulence not linked
Infants and elderly are at utmost risk
All age groups including healthy adults
This is result of Antigenic Drift
This is result of Antigenic Shift
Vaccine available; Modified each year
No vaccine available as it’s a novel virus
Deaths
Subtype
Pandemic
Severity Index
I Million
? H2N2
NA
Spanish Flu 1918 Pandemic 1918 - 1920
50 Million
H1N1
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Asian Flu
1957 - 1958
4 Million
H2N2
2
Hong Kong Flu
1968 - 1969
2 Million
H3N3
2
2009 Flu Pandemic
2009 – Present
 4, 735
H1N1v
About 1.5
Seasonal Influenza
Every Year
500, 000
H1N1
NA
Name of the Pandemic
Asiatic (Russian) Flu
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Year
1889 - 1890
• We’re still learning about the severity of the novel H1N1
• At this time, there is not enough information to predict
how severe this novel H1N1 flu outbreak will be in terms
of illness and death or
• It compares very similar to seasonal influenza.
• Luckily most cases have been mild. Only few fatal cases
• Most people recover without hospitalization or Tamiflu
• It may mutate eventually and become more / less serious.
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Second Wave
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WHO - Region wise
As of 8th Nov 09
Cases
Deaths
WHO RO for Africa – AFRO
14,868
103
1,90,765
4,512
25,531
151
> 78,000
300
44,661
678
WHO RO for Western Pacific – WPRO
1,49,711
516
Total
> 5,03,536
6,260
WHO RO for the Americas – AMRO
WHO RO for Eastern Mediterranean – EMRO
WHO RO for Europe - EURO
WHO RO for South-East Asia – SEARO
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CFR = (6260 ÷ 5,03,536) x 100 = 1.243%
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As on 08th November 2009
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Mortality Rate =
150 ÷1,00,000 =
0.15%
Clinical Attack
Rate = 10,000 ÷
50,000 = 20%
Exposed
1,00,000
Infected
50,000
Clinical
Cases
Hospital
CFR = 150 ÷
10,000 or 1.5%
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Death
10,000
1,000
150
Influenza A H1N1 Status as on 11th November 09
State
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Cumulative Cases Cumulative Death State
Cumulative Cases Cumulative Death
Delhi
3659
17
Gujarat
256
40
Andhra Pradesh
765
49
Manipur
1
0
Karnataka
1513
118
Meghalaya
8
0
Tamil Nadu
1654
7
Mizoram
4
1
Maharashtra
3768
209
Assam
45
0
Kerala
1124
22
Jharkhand
1
0
Punjab
45
2
Rajasthan
230
19
Haryana
814
5
Bihar
7
0
Chandigarh
74
0
Uttar Pradesh
451
3
Goa
54
4
Puducherry
54
6
West Bengal
127
0
Chattishgarh
16
1
Uttarakhand
74
Madhya Pradesh
7
0
Himachal Pradesh
6
Orissa
19
1
Jammu & Kashmir
47
3
1
0
14851
508
Total
CFR = (508 ÷ 14851) x 100 = 3.42 %
• Very Similar to the Seasonal Flu and Not like Common Cold
– Moderate to high fever
– aches, muscle and joint pains
– chills and fatigue
– sore throat, head ache
– cough
– sneezing and running nose
– shortness of breath, chest pain on breathing
– diarrheas and vomiting (possible), loss of appetite
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• Onset of acute febrile respiratory illness within 7 days of close
contact with a person who has a confirmed case of H1N1
influenza A virus infection, or
• Onset of acute febrile respiratory illness within 7 days of travel
to a community (within the United States or internationally)
where one or more H1N1 influenza A cases have been
confirmed, or
• Acute febrile respiratory illness in a person who resides in a
community where at least one H1N1 influenza case has been
confirmed.
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Fever or H/o Fever
87%
Head ache
41%
Myalgia
38%
Arthralgia
23%
Diarrhea
12%
Dry cough
49%
Vomiting
16%
Productive cough
17&
Nausea
17%
Sore throat
49%
Conjunctivitis
7%
Running nose
33%
Nose bleed
2%
Sneezing
21%
Altered Sensorium
0.5%
Shortness of Breath
10%
Others
22%
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Present
Pandemic
1918
Pandemic
Serial Interval - SI
1.9
2.6
Less severe
Basic Reproductive Rate – R0
1.2
1.8
Less severe
Heard Immunity – HI
17%
NA
Will build up
Serial Transmission Cycles
?2
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Less severe
Infected population %
20%
>60%
Less severe
? 1.5 /1000
25%
Mild
Parameter
Case fatality rate – CFR
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Comment
• Secondary attack rate in household contacts: 12 %.
• Overall proportion of hospitalizations: 8 %.
• Overall case fatality: 0.15 % or 1.5 per every 1000 cases
• Most cases (58 %) highest incidence in 5–24 years age group,
• Second highest incidence in children < 5 years
• Most hospitalizations (34 %) in 5–24 years age group,
• Highest age-specific hospitalization rate in children < 5 years
• Most deaths in 5–24 years age group
• The old are generally spared > 65
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• Cocktail mix of Porcine, Avian and Human Influenza A Virus
• Direct Airborne, No other routes so far
– Fine droplets expelled during coughing and sneezing
– Expectorated sputum and the dried secretion
• Indirect - All items that have been in contact with a patient (Fomite)
• Incubation Period (IP) – 3 to 7 days – Median 2-3 days
• Contagious period – One day before symptoms to 7 days
• Asymptomatic carrier state – None
• Immunity – Life time for this type; No protection by seasonal flu
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Isolation
• Separation and restricted movement of ill persons with
contagious disease, often in a hospital setting
• Primarily individual level; Can be voluntary or mandated
Quarantine
• Separation and restriction of movement or activities
of persons who are, not yet ill, have been exposed
• Often at home, or residential facility or hospital Individual
or community level; Can be voluntary or legally mandated
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• Diabetes
• Pregnancy
• Chronic Respiratory Illnesses , Neuromuscular disorders
• Chronic cardio-vascular disease (? hypertension)
• Seizure disorder and other neurodegenerative disease
• Chronic renal disease stages III and IV
• Cancer and immuno suppression including HIV
• Morbid Obesity
• More deaths in people <18 years of age
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• Children < 5 years old; Persons aged 65 years or older
• Children and adolescents (< 18 years) who are receiving
long-term aspirin therapy and at risk for Reye syndrome
• Pregnant women
• Adults and children who have asthma, chronic pulmonary,
cardiovascular, hepatic, hematological, neurologic,
neuromuscular, or metabolic disorders such as diabetes;
• Adults and children who have immuno-suppression
(either due to medications or by HIV)
• Residents of nursing homes and other chronic-care facilities.
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• rRT-PCR Swine Flu assay– reverse transcriptase real time PCR
– Highly specific test, 24 to 48 hours, costly Rs. 4,000, detects viral
multiplication, can identify the novel H1N1 correctly
– Confirmatory test, sensitivity is also quite high 85%, Quantitative
• RIDT (Rapid Influenza Diagnostic Test) – Not Recommended
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point of care, 1 hour, less cost (Rs 700), card test, detects viral protein
Sensitivity low 10 to 70% - A negative result can’t exclude Influenza
Can not distinguish between Influenza B or A or A sub types
Specificity – 80% - can confirm Influenza infection – not the type
If positive – needs a confirmatory test to identify the type
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