H1N1/SWINE FLUNavpreet Sahsi

INFLUENZAGlobally 250,000 to 500,000 deaths per yearIn the US (per year)35,000 deaths> 200,000 hospitalizations$10 billion in lost productivity

HISTORICALLYIllness 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 deathMore than 40 million people vaccinatedProgram was stopped short after 500 cases of GBS and 30 reported deaths as direct result of vaccineBetween 1958 2005, 37 additional cases of swine influenza were reportedSix cases of death

ZIMMER SM. NEJM 2009 361:279

2009 PANDEMICMarch/April 2009, outbreak of respiratory illnesses first noted in Mexico, eventually identified as related to H1N1 influenzaApril 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 continentsJuly 6 10,200 confirmed cases in Mexico with 119 deathsJuly 24 43,000 cases confirmed in US

CHOWELL G. ET AL. NEJM 2009; 361: 274.

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.

TRANSMISSIONPerson to personVirus in present in respiratory secretionssneezing and coughing via large particle droplets or by aerosolized small-particle dropletsContact with surfaces contaminated with dropletsPossibility of transmission from other bodily fluids (eg. Diarrheal stool)

PATIENT MYTHSYou 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.

YOU THINK YOU KNOW SWINE FLU?Incubation period?

A) 0 1 daysB) 1 - 4 daysC) 7 daysD) 14 days

Answer:

Well, precise incubation period has not been established but presumed to be..

B) 1 4 days

INFECTIVITY?A) One day prior to symptoms and one day post symptomsB) One week prior to symptoms and one day post symptomsC) One day prior to symptoms and one week post symptomsD) One week prior to symptoms and one week post symptoms

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

CLINICAL MANIFESTATIONSSimilar to those of seasonal influenzaGI findings have been more common than with seasonal influenzaCommonlyFeverCoughSore throatMalaiseHeadacheVomiting DiarrheaArthralgias

Remember - Atypical presentations in infants, elderly, immunocompromised

HIGH RISK GROUPSWho?

HIGH RISKChildren younger than 5 yearsAge > 65Less than 19 receiving long-term ASA therapy (Risk of Reyes syndrome after infx)Pregnant WomenChronic DiseasesCOPDCVD (except isolated HTN)CRFChronic Liver diseaseDMImmunosuppression eg. HIV, transplant patientsPoor handling of resp. secretions eg. CF, cerebral palsy, spinal cord injuries, seizure disorders, NM disease

What about obesity?

Not officially recognized as a risk factor but a disproportionate # of cases of severe H1N1 have been reported without underlying conditions

COMPLICATIONSAbout 2 to 5% of confirmed cases in the US and Canada have required hospitalization 6% in MexicoOf hospitalized patients, large majority fall into high risk category (75 85% in one study)Many reported cases of rapidly progressive pneumonia, respiratory failure, ARDSMost complications similar to seasonal fluURTIs (sinusitis, otitis media, croup)LRTIs (pneumonia, brochiolitis, status asthmaticus)Cardiac (myocarditis, pericardits)Neuro (encephalopathy/encephalitis, febrile seizures, status epilepticus)Toxic Shock syndromeSecondary bacterial pneumonia

DIAGNOSISWho to test?

Basics- Those who will require hospitalizationThose who are at high risk for severe complications (High risk group)

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

From Alberta Health Services

If mild ILI symptoms NO LAB TESTINGMild ILI and high risk NP swab consideredSevere symptoms (admission to hospital) or SRI NP swab plus additional testing as appropriate

Note turn around time for NP swab 3 days

TREATMENTCurrently vast majority of strains appear sensitive to neuraminidase inhibitors oseltamivir (Tamiflu) and zanamivir (Relenza)How soon to treat?A) ASAPB) Within 24 hoursC) Within 48 hoursD) Within 96 hoursE) Within 7 days

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

WHO GETS TAMIFLU?Basics All hospitalized patients with confirmed or suspected H1N1 infectionPatients at increased risk for complicationsIf youre thinking about swabbing them, you should at least be thinking about treating them.

DOSINGTreatment - Tamiflu 75 mg PO BID x 5 daysProphylaxis 75 mg PO OD x ?

Relenza 10 mg (2 puffs) BID x 5 daysProphylaxis 10 mg OD

WHAT ABOUT KIDS?Tamiflu approved in US/Canada in individuals > 1 year of age, Relenza > 7 years oldLimited safety data on kids < 1 yearFrom 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 BIDIf no weight measures then by age:0 3 months 12 mg BID3 5 months 20 mg BID6 11 months 25 mg BID

PREGGERS?True or False:

Tamiflu and Relenza are safe in pregnant women

True!!!

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

PREGGERS?When are pregnant women most susceptible to H1N1 virus?

A)First TrimesterB) Second TrimesterC) Third TrimesterD) Immediately post - partum

AnswerC) Third Trimester

However, women are at increased susceptibility during second trimester until about 4 weeks post-partum.

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?

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

REFERENCESZimmer, 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 Canadawww.phac-aspc.gc.ca/alert-alerte/swine-porcine/hp-index-eng.phpWorld Health Organization Influenza A (H1N1)www.who.int/csr/disease/swineflu/en.index.htmlAlberta Health Serviceswww.calgaryhealthregion.ca/moh/professional.htmEpidemiology, clinical manifestations, and diagnosis of pandemic H1N1 influena (swine influenza) www.uptodate.comTreatment of pandemic H1N1 influenza (swine influenza) www.uptodate.com