Transcript Slide 1

1918 influenza victims crowd an emergency hospital at Fort Riley, Kansas.
Influenza Update
Best Practices
Jason Cohen, MD
Assistant Professor of Internal Medicine
Hospitalist Section
10/30/09
Goals of Presentation
Review basic science of influenza.
Discuss status of current influenza outbreak and its
historical context.
Propose referral, admission, treatment and discharge
criteria for patients with influenza-like illness.
What is Influenza
Virus of the Orthmyxoviridae family.
Genome consists of 8 single-stranded RNA segments.
Designation of influenza viruses as A, B or C based on characteristics
of nucleoprotein and matrix protein antigens. The most severe and
extensive outbreaks have been caused by influenza A viruses.
Influenza A further subdivided based on surface antigens Hemagglutinin (H) and Neuraminidase (N).
H what, n what?
Three major antigenic subtypes of Hemagglutinin (H1, H2, H3) and
two major subtypes of Neuraminidase (N1, N2)recognized in human
infection.
Hemagglutinin allows virus to bind and enter the cell.
Neuraminidase allows virus to exit cell and spread infection.
Antibodies to Hemagglutinin determine immunity, while those to
Neuraminidase limit viral spread and contribute to reduction of
infection.
Minor changes in Hemagglutinin and Neuraminidase occur through
antigenic drift, while major variations are the result of antigenic shift.
1957 pandemic a result of antigenic shift from H1N1 to H2N2.
16 subtypes of Hemagglutinin and 9 subtypes of
Neuraminidase circulate in wild and domestic bird populations
Is this the same h1n1 that killed 30 million
people in 1918?
Yes and No.
It has the same Hemagglutinin and Neuraminidase
proteins on its outside, but is a different strain. The
strain that caused the 1918 pandemic was able to infect
pigs but not kill them. The virus adapted to the pigs and
is thought to have contributed to the current lineage of
H1N1 “swine” influenza. The current virus has two
genes from viruses that normally circulate in pigs, and
avian and human genes (a “quadruple reassortant
virus.”)
The new H1N1 is missing a particular amino acid that is
Match the flu
1) Spanish Flu
a) Pandemic of 1889
2) Avian Flu
b) H3N2
3) Asian Flu
c) Pandemic of 1918
4) Hong Kong Flu
d) H5N1
5) Russian Flu
e) Pandemic of 1957
The Typical Flu Season...
Runs from November thru May.
Contributes to somewhere around 200,000
hospitalizations.
Is responsible for 36,000 deaths.
60% of hospitalization typically occur in those over 65.
Where are we now?
Between August 30th and October 17th, 8,204 laboratory-confirmed
hospitalizations for H1N1 in the United States.
During same time period, 411 laboratory-confirmed H1N1 deaths.
Over half of hospitalizations (53%) for H1N1 have occurred in people
under the age of 25.
One-third of deaths have been in people 25-49 years old, and one-third
in patients age 50-62. In a typical flu season, 90% of deaths are in
patients over age 65.
Percentage of Visits for Influenza-like Illness (ILI) Reported by the U.S. Outpatient Influenza-like Illness Surveillance Network
(ILINet), National Summary 2008-2009 and Previous Two Seasons
(Posted October 23, 2009, 5:30 PM ET, for Week Ending October 17, 2009)
Where are we headed?
Latest CDC update showed a continued increase in the number of reported cases
of H1N1 and visits to physicians and hospitals.
Number of visits, hospitalizations, and deaths all higher than what would be
expected for this time of year.
At UNMH, 38 patients on expanded droplet precautions (17 with confirmed
H1N1.)
Half of ICU beds taken up by H1N1 patients (almost all on ventilators.)
UNMH has seen a decrease over the last week in the number of visits to the flu
clinic (peaked at 60 visits/day, currently at 30-40 visits/day.)
Still can’t decide what to wear to the
Halloween Party?
Vaccination
Recommendations
The CDC recommends that the following groups be
prioritized for receipt of the H1N1 vaccine as it becomes
available:
1. pregnant women
2. people who live with or care for children younger than 6 months of age
3. health care and emergency medical services personnel with direct patient
contact
4. children 6 months through 4 years of age
5. children 5 through 18 years of age who have chronic medical conditions
*As of October 16, 2009, the CDC predicts that there will not be a shortage of vaccine (though supply may
be unpredictable.)
Diagnosis of H1N1
Symptoms: fever (95%), headache, cough (88%), sore throat,
myalgias, chills, malaise, runny nose - and in the case of H1N1,
diarrhea and vomiting (39%).
ILI is defined as fever (temperature of 100°F [37.8°C] or greater)
and a cough and/or a sore throat in the absence of a known cause
other than influenza.
Patients with symptoms of uncomplicated influenza do not
require diagnostic testing for clinical management.
Clinical Testing
Rapid influenza diagnostic tests are reactive with the
nucleoprotein of H1N1, but lack sensitivity (10 - 70%)
Positive results of RIDTs may be used to guide therapy (high
specificity) but negative results should be interpreted with
caution.
The CDC recommends that rRT-PCR testing should be
performed when definitive determination of influenza infection
is necessary.
See http://www.cdc.gov/h1n1flu/guidance/rapid_testing.htm#ftn4 for Interim Guidance
for the Detection of Novel Influenza A Virus
When is PCR testing
necessary?
Hospitalized patients with suspected influenza
Patients for whom a diagnosis of influenza will inform
decisions regarding clinical care, infection control, or
management of close contacts.
Patients who died of an acute illness in which influenza
was suspected.
See further recommendations at www.cdc.gov/h1n1flu/guidance/diagnostic_tests.htm
Who Requires
Hospitalization?
No clear guidelines from the CDC.
NHS published an algorithm suggesting that the
following criteria be met for discharge from the ER:
1) Absence of respiratory distress
2) Respiratory rate ≤ 30
3) SpO2 ≥ 92% on room air
4) No evidence of dehydration
5) Tolerating oral fluids
Cohorting of H1N1 patients
The CDC recommends single-patient rooms when available,
prioritizing patients with excessive cough or sputum production.
If necessary, okay to cohort patients that are infected with the same
organism.
If necessary to place a patient on droplet precautions with a patient
who does not have the same infection, avoid placement with
immunocompromised patients or patients at high risk for
complications.
Assure patients are at least 3 feet apart and keep curtain pulled
between patients.
Isolation of H1N1 patients
The CDC continues to recommend use of N95 masks despite recent studies that
suggest the non-inferiority of surgical masks. UNMH has made the decision to use
surgical masks.
Where there is a high risk for aerosolization of respiratory secretions (intubation,
bronchoscopy,) N95 masks are appropriate.
Non-sterile gloves should be worn when contact with potentially infectious
materials is anticipated.
Isolation precautions for patients who have influenza symptoms should be
continued for the 7 days after illness onset or until 24 hours after the resolution of
fever and respiratory symptoms, whichever is longer, while a patient is in a
healthcare facility.
Treatment of hospitalized patients with
H1N1
Oseltamivir 75mg po BID for 5 days
In patients who are persistently febrile, oseltamivir
may be continued for a longer duration.
Patients with chest x-ray abnormalities should be
treated with antibiotics for community-acquired or
healthcare-associated pneumonia, as appropriate.
Peramivir available through clinical trial (Drs. Goade
and Kellie) and emergency use authorization from
FDA.
When to treat with
oseltamivir
UNMH Infection Control has recommended treating
all patients admitted with respiratory infections or
exacerbations of chronic respiratory conditions.
Data suggests that earlier treatment improves
outcomes - do not delay initiation of oseltamivir while
awaiting rRT-PCR results.
Treat patients regardless of the duration of their
symptoms. Hospitalized patients may benefit even if
therapy is started more than 48 hours after onset of
Still undecided? Consider the old standbys.
Proposed Admission Order Set
Proposed discharge criteria
for H1N1
Afebrile for ≥ 24 hours.
Able to tolerate PO.
Stable or decreasing oxygen requirement of 4 liters or
less with ambulation.
Follow-up Care
Patients with chronic medical conditions should be
seen by a healthcare provider within 5-10 days
following discharge.
Patients without significant comorbidities do not
require routine follow-up.
Patient found to have abnormal chest x-ray findings
during hospitalization should have repeat chest x-ray
in 4-6 weeks following discharge to document
resolution.
Treatment modalities are
limited.
Hospitalization and
complications are high.
Defense is the best
offense.
Wash your hands.
Get Vaccinated.
References
Faix DJ, Sherman SS, Waterman SH. Rapid-Test Sensitivity for Novel Swine-Origin Influenza A (H1N1) Virus in Humans. N Engl J Med. 2009
Jun 29
Hurt AC et al. Performance of influenza rapid point-of-care tests in the detection of swine lineage A(H1N1) influenza viruses. Influenza and
Other Respiratory Viruses 2009;3(4):171-76
Thompson WT et al. Influenza-Associated Hospitalizations in the United States. JAMA 2004;292:1333-1340.
Loeb M et al. Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers.
JAMA. 2009;302(17):(doi:10.1001/jama.2009.1466).
Harrison’s Principles of Internal Medicine, 15th edition.
Bar SA, Herrington JD, Busti AJ, et al. Is oseltamivir effective if administered greater than 48 hours after the onset of flu-like symptoms from
the swine-origin influenza A (H1N1) viral infection? PW Pharmacother Newsl 2009;1(23):1-4.
McGeer A, Green KA, Plevneshi A et al. Antiviral therapy and outcomes of influenza requiring hospitalization in Ontario, Canada. Clin Infect
Dis 2007;45;1568-75.
Jain S et al. Hospitalized Patients with 2009 H1N1 Influenza in the United States, April-June 2009. NEJM. 2009;361(epub ahead of
publication.)
Interim Recommendations for Clinical Use of influenza Diagnostic Tests During the 2009-10 Influenza Season.
www.cdc.gov/h1n1flu/guidance/diagnostic_tests.htm
Interim Guidance for the Detection of Novel Influenza A. http://www.cdc.gov/h1n1flu/guidance/rapid_testing.htm#ftn4
Swine flu clinical package for use when there are exceptional demands on healthcare services. Department of Health, United Kingdom.
http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_106495