H1N1/SWINE FLU

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H1N1/SWINE FLU

• Navpreet Sahsi

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INFLUENZA

• Globally 250,000 to 500,000 deaths per year
• In the US (per year)
• 35,000 deaths
• gt 200,000 hospitalizations
• 10 billion in lost productivity

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HISTORICALLY

• Illness with influenza from pigs was first
  recongnized during influenza pandemic of 1918 (40
  50 million deaths)
• 1976 Swine flu outbreak occurred in Fort Dix
  New Jersey that caused more than 200 cases with
  serious illness in several people and one death
• More than 40 million people vaccinated
• Program was stopped short after 500 cases of GBS
  and 30 reported deaths as direct result of
  vaccine
• Between 1958 2005, 37 additional cases of swine
  influenza were reported
• Six cases of death

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ZIMMER SM. NEJM 2009 361279
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2009 PANDEMIC

• March/April 2009, outbreak of respiratory
  illnesses first noted in Mexico, eventually
  identified as related to H1N1 influenza
• April 17, 2009 2 cases in California of
  children in neighbouring counties
• June 24 WHO raised pandemic alert level to
  phase 6 widespread community transmission on
  two continents
• July 6 10,200 confirmed cases in Mexico with
  119 deaths
• July 24 43,000 cases confirmed in US

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CHOWELL G. ET AL. NEJM 2009 361 274.
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AT HOME

• - June 10, 2009 47 cases in the Calgary area,
  and 2978 nationwide with 4 deaths
• - August 9, 2009 no longer keeping track of
  cases 64 deaths nationwide, 6 in Alberta.

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TRANSMISSION

• Person to person
• Virus in present in respiratory secretions
• sneezing and coughing via large particle droplets
  or by aerosolized small-particle droplets
• Contact with surfaces contaminated with droplets
• Possibility of transmission from other bodily
  fluids (eg. Diarrheal stool)

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PATIENT MYTHS

• You can get the swine flu from eating pork.
• I got my flu shot this winter, so Im protected
  from the swine flu.
• You can only get swine flu from direct contact
  with a pig.
• Taking vitamins can protect against influenza.

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YOU THINK YOU KNOW SWINE FLU?

• Incubation period?
• A) 0 1 days
• B) 1 - 4 days
• C) 7 days
• D) 14 days

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• Answer
• Well, precise incubation period has not been
  established but presumed to be..
• B) 1 4 days

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INFECTIVITY?

• A) One day prior to symptoms and one day post
  symptoms
• B) One week prior to symptoms and one day post
  symptoms
• C) One day prior to symptoms and one week post
  symptoms
• D) One week prior to symptoms and one week post
  symptoms

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• C ) One day prior to symptoms and one week post
  symptoms

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CLINICAL MANIFESTATIONS

• Similar to those of seasonal influenza
• GI findings have been more common than with
  seasonal influenza
• Commonly
• Fever
• Cough
• Sore throat
• Malaise
• Headache
• Vomiting
• Diarrhea
• Arthralgias
• Remember - Atypical presentations in infants,
  elderly, immunocompromised

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HIGH RISK GROUPS

• Who?

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HIGH RISK

• Children younger than 5 years
• Age gt 65
• Less than 19 receiving long-term ASA therapy
  (Risk of Reyes syndrome after infx)
• Pregnant Women
• Chronic Diseases
• COPD
• CVD (except isolated HTN)
• CRF
• Chronic Liver disease
• DM
• Immunosuppression eg. HIV, transplant patients
• Poor handling of resp. secretions eg. CF,
  cerebral palsy, spinal cord injuries, seizure
  disorders, NM disease

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• What about obesity?
• Not officially recognized as a risk factor but a
  disproportionate of cases of severe H1N1 have
  been reported without underlying conditions

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COMPLICATIONS

• About 2 to 5 of confirmed cases in the US and
  Canada have required hospitalization
• 6 in Mexico
• Of hospitalized patients, large majority fall
  into high risk category (75 85 in one study)
• Many reported cases of rapidly progressive
  pneumonia, respiratory failure, ARDS
• Most complications similar to seasonal flu
• URTIs (sinusitis, otitis media, croup)
• LRTIs (pneumonia, brochiolitis, status
  asthmaticus)
• Cardiac (myocarditis, pericardits)
• Neuro (encephalopathy/encephalitis, febrile
  seizures, status epilepticus)
• Toxic Shock syndrome
• Secondary bacterial pneumonia

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DIAGNOSIS

• Who to test?
• Basics
• - Those who will require hospitalization
• Those who are at high risk for severe
  complications (High risk group)

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• Important definitions (from CDC)
• Influenza-like illness (ILI) fever (T gt 37.8)
  with cough or sore throat in absence of known
  cause other than influenza
• Severe Respiratory Illness (SRI) respiratory
  symptoms including history of fever gt 38, new
  onset of cough or breathing difficulty, with
  severe illness progression within first 72 hours
• Pneumonia, ARDS, encephalitis, or other severe
  and life threatening complications

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• From Alberta Health Services
• If mild ILI symptoms NO LAB TESTING
• Mild ILI and high risk NP swab considered
• Severe symptoms (admission to hospital) or SRI
  NP swab plus additional testing as appropriate
• Note turn around time for NP swab 3 days

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TREATMENT

• Currently vast majority of strains appear
  sensitive to neuraminidase inhibitors
  oseltamivir (Tamiflu) and zanamivir (Relenza)
• How soon to treat?
• A) ASAP
• B) Within 24 hours
• C) Within 48 hours
• D) Within 96 hours
• E) Within 7 days

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• Obviously A) therapy should begin as soon as
  possible
• However, evidence of benefit in seasonal
  influenza is strongest for treatment within 48
  hours
• CDC still recommends therapy even after 48 hours
  of illness since some studies of hospitalized
  patients have demonstrated benefit

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WHO GETS TAMIFLU?

• Basics
• All hospitalized patients with confirmed or
  suspected H1N1 infection
• Patients at increased risk for complications
• If youre thinking about swabbing them, you
  should at least be thinking about treating them.

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DOSING

• Treatment - Tamiflu 75 mg PO BID x 5 days
• Prophylaxis 75 mg PO OD x ?
• Relenza 10 mg (2 puffs) BID x 5 days
• Prophylaxis 10 mg OD

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WHAT ABOUT KIDS?

• Tamiflu approved in US/Canada in individuals gt 1
  year of age, Relenza gt 7 years old
• Limited safety data on kids lt 1 year
• From Health Canada
• Health Canadas Interim Order permits the
  expanded use of oseltamivir as a treatment or
  prophylaxis for children under 1 year of age, for
  infection caused by the pandemic (H1N1) 2009
  virus due to recent clinical data suggesting its
  comparable safety profile identified in children
  over 1.
• Dosing in children 2 mg/kg PO BID
• If no weight measures then by age
• 0 3 months 12 mg BID
• 3 5 months 20 mg BID
• 6 11 months 25 mg BID

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PREGGERS?

• True or False
• Tamiflu and Relenza are safe in pregnant women

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• True!!!
• Pregnancy category C meaning that clinical
  studies not done. But no adverse events noted.
  Health Canada states that current benefits
  outweigh risks.

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PREGGERS?

• When are pregnant women most susceptible to H1N1
  virus?
• A)First Trimester
• B) Second Trimester
• C) Third Trimester
• D) Immediately post - partum

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• Answer
• C) Third Trimester
• However, women are at increased susceptibility
  during second trimester until about 4 weeks
  post-partum.

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BREASTFEEDING?

• You decide to treat a woman who is two weeks
  post-partum that presents with worrysome
  respiratory symptoms.
• She asks you if it is safe to breast feed her
  newborn baby while on antiviral therapy. What do
  you tell her?

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• Safe!!
• Due the anti-infective benefits of human milk
  for infants and the low dosages of antiviral
  passed to the baby through breastmilk, it is
  recommended that women continue to breastfeed
  their baby when taking antiviral medications.
  Health Canada
• Dosing same as in other adults 75 mg PO BID
  or 10 mg inhaled BID.
• Preferred agent is Zanamivir (Relenza) in
  pregnant/breastfeeding women although both safe.
  Alberta Health Services

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REFERENCES

• Zimmer, SM. Historical Perspective Emergence of
  Influenza A (H1N1) Viruses. NEJM 2009 361 279
  285.
• Chowell, G. et al. Severe Respiratory Disease
  Concurrent with the Circulation of H1N1
  Influenza. NEJM 2009 361 674-679.
• Public Health Agency of Canada
• www.phac-aspc.gc.ca/alert-alerte/swine-porcine/hp-
  index-eng.php
• World Health Organization Influenza A (H1N1)
• www.who.int/csr/disease/swineflu/en.index.html
• Alberta Health Services
• www.calgaryhealthregion.ca/moh/professional.htm
• Epidemiology, clinical manifestations, and
  diagnosis of pandemic H1N1 influena (swine
  influenza) www.uptodate.com
• Treatment of pandemic H1N1 influenza (swine
  influenza) www.uptodate.com