Transcript Back To The Future: the 2009 H1N1 Pandemic

Back To The Future:
2009 nH1N1 (S-OIV) Pandemic
Edward L. Goodman, MD
November 10, 2009
Descriptive Epidemiology
• 1918 experience
• Subsequent pandemics in 20th century
• Basic virology
– Antigenic drift and shift
– Pigs as mixing vessels
• The nH1N1 pandemic
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Epidemic Curves
Age related attack rate
Age related morbidity
Unique risk groups
• Pregnancy
• Children
– Mixed viral and bacterial infection
The 1918 Pandemic
• “Those who cannot remember the past are
condemned to repeat it”
– Santayana, G. Reason in Common Sense
1905
Origins of a Pandemic
• February 1918, Haskell County, Kansas
– Violent influenza reported by Loring Miner,
MD
– Notified USPHS who ignored him
• March 4, 1918, Camp Funston, Kansas
– A cook reported for sick call
– Within 3 weeks: 1100 soldiers admitted
• 237 (20%) developed pneumonia
• 38 died
Spread
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Philadelphia Naval Yard
Boston
Throughout the US East Coast
To Europe with the soldiers
Ultimately world wide including Alaska,
Asia, Africa
• Spared much of Australia
– Strict quarantine of all ships
The Cost
• USA: 675,000 deaths out of population of 105
million (0.65%)
• Worldwide: 50 to 100 million out of 1.8 billion
died (5% of world’s population)
– 2009: world population is 6.3 billion
– Death would have occurred in 73 to 350 million
• Distribution of deaths: more than half between
ages of 16 and 40 (ages 21-30 had the highest
death rates)
• Late onset neurologic disorders (Parkinson’s
Disease)
Descriptive Epidemiology of a Pandemic
And then…….
Epidemic Curves
Dallas County Texas
Dominant Strain
Morbidity and Mortality
• Ambulatory Cases are not tracked by
Health Departments
• Hospitalized cases are reportable
– Surrogate for severity
– More often have viral studies done
77 Autopsies reported to CDC. MMWR Oct 2, 2009
Pediatric Deaths
• Through Oct 17 2009 100 deaths reported
in children
• First 36 deaths were reported in detail
Why Children Are So Vulnerable
• They have no prior exposure to similar
virus
– Thus, they have no cross reactive antibody
Why So Vulnerable?
• Young adults may be immunologically
naïve but they have robust cellular
immune system
• ARDS pathophysiology
– Osterholm, MT. Preparing for the Next Pandemic.
NEJM 2005; 352:1839-42
Proposed Mechanism of the Cytokine Storm Evoked by Influenzavirus
Osterholm, M. T. N Engl J Med 2005;352:1839-1842
Another Highly Vulnerable Group:
Pregnant Women
Deaths in Pregnant Women
Controversies and Questions
• Should Rapid Flu Testing be done
routinely?
Diagnosis - Rapid Antigen Tests
Viral antigen
in respiratory
secetions;
nucleoprotein
30 min.
Sensitivity 4080%
Specificity
85-100%
Cost $20
Comparison of Available Influenza Diagnostic Tests
(CDC, 09/29/09)
Tests
Method
Availability
Process
time
Sens.H1N1, Disting. S’09
OIV/others
RIDT
Ag.
Detect.
Wide
0.5 hour
10-70%
No
DFA/IFA
Ag.Detect.
Wide
2-4
hours
47-93%
No
Culture
Virus isol. Limited
2-10
days
Unknown Yes@
NAAT*
RNA
detect.
TAT 4896 hours
86-93%
* Incl.rRT-PCR
@Requires
tests
addl.
Limited
Yes
Controversies and Questions
• Should antiviral treatment be routine?
• Should routine antiviral chemoprophylaxis
be given to exposed persons?
77 Autopsies reported to CDC. MMWR Oct 2, 2009
Controversies and Questions
• Who should be vaccinated?
• Why the problems with vaccine?
Problems with the monovalent
H1N1 vaccine
• Low yield in egg yolk cultures
• Problems with distribution
– Inopportune time for getting health care
reform!
• Talking heads from political left and right
Controversies and Questions
• What kind of Personal Protective
Equipment is needed to take care of a
patient with possible nH1N1 influenza?
CDC pronouncements
• April 2009
– Need airborne isolation rooms with negative
pressure
• Push back from hospitals because of limited
number of negative pressure rooms
– Need N95 masks
– Infected health care workers need to stay
home for one week since onset of symptoms
• Push back from hospitals because of projected
shortages of HCW
CDC modifications
• May 2009
– Isolation in private room or with another
infected patient
• No longer require airborne isolation/negative
pressure
• October 2009
– Infected HCW can return to work after afebrile
for 24 hours on no anti-pyretic
How about N95 respirators?
• More expensive
– $0.53 for N95 vs. $0.07 for surgical
– Multiply by thousands of masks used in caring
for patients across the system!
• Hard to wear for prolonged periods
– In Loeb JAMA Oct 1, 2009 only 87%
compliance with N95 vs 100% for surgical
• Unnecessary for droplet transmission
Interim Conclusions
• H1N1 illness is generally mild and self limited
• Vulnerable groups should be treated even for mild illness
– Children <2r 4 years old; adults >65 yo
– Pregnant women
– Young adults (5-24) with co-morbidities
• Patients ill enough to be admitted
– Should receive neuraminidase inhibitors
• Promptly and best within two days of onset
• May be effective for severe disease even if given later
– Should be considered for anti-bacterial therapy early
• Use infection prevention hierarchy
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Vaccinate those most vulnerable
Respiratory etiquette
Hand hygiene
Surgical masks except for aerosol generating procedures
Any Questions?