influenza
DESCRIPTION
TRANSCRIPT
Saturday, May 29, 2010
INFLUENZA
Jaime A. Santos
Saturday, May 29, 2010
Influenza
• commonly called “the flu”
• a contagious respiratory illness caused by influenza viruses
• Infection with influenza viruses can result in illness ranging from mild to severe with life-threatening complications
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Saturday, May 29, 2010
1918 Spanish flu pandemic: 20 to 50 million people may have died worldwide
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Viral Titers Peak Early
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“Flu” symptoms
Fever/ chills
Headache
Nasal congestion
Sore throat
Dry cough
Myalgia/ body aches
GI symptoms
Malaise/ tiredness
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Influenza - Clinical Signs and Symptoms
• incubation period for influenza is 1--4 days, with an average of 2 days
• Adults - infectious from the day before symptoms begin through approximately 5 days after onset
• Children - infectious for > 10 days, and young children can shed virus for < 6 days before their illness onset
• immunocompromised persons can shed virus for weeks or months
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Influenza - Clinical Signs and Symptoms
• resolves after a limited number of days for the majority of persons, although cough and malaise can persist for >2 weeks
• young children can have initial symptoms mimicking bacterial sepsis with high fevers– < 20% of children hospitalized with
influenza can have febrile seizures
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Influenza - Clinical Signs and Symptoms
• Influenza infection has also been associated with encephalopathy transverse myelitis Reye syndrome myositis myocarditis pericarditis
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Influenza - Hospitalization and Deaths• Population at risk for complications,
hospitalizations, & deaths:> 65 years old– young children– persons of any age with certain
underlying health conditions: cardiovascular and pulmonary (including asthma), metabolic e.g. DM, Hgbpathies, immunosuppression
– receiving long term ASA
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“U” Shaped Epidemic Curve of Influenza During the Interpandemic Period
Visits/100ARD Hospitalizations/10,000P&I Mortality/100,000
Rate
Age group
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“U” Shaped Epidemic Curve of Influenza During the Interpandemic Period
< 5 5–9 10–14 15-19 20-24 25-34 35-44 45-54 55-64 > 640
20
40
60
80
100
120 Visits/100ARD Hospitalizations/10,000P&I Mortality/100,000
Rate
Age group
Saturday, May 29, 2010
“U” Shaped Epidemic Curve of Influenza During the Interpandemic Period
< 5 5–9 10–14 15-19 20-24 25-34 35-44 45-54 55-64 > 640
20
40
60
80
100
120 Visits/100ARD Hospitalizations/10,000P&I Mortality/100,000
Rate
Age group
Saturday, May 29, 2010
“U” Shaped Epidemic Curve of Influenza During the Interpandemic Period
< 5 5–9 10–14 15-19 20-24 25-34 35-44 45-54 55-64 > 640
20
40
60
80
100
120 Visits/100ARD Hospitalizations/10,000P&I Mortality/100,000
Rate
Age group
Saturday, May 29, 2010
“U” Shaped Epidemic Curve of Influenza During the Interpandemic Period
< 5 5–9 10–14 15-19 20-24 25-34 35-44 45-54 55-64 > 640
20
40
60
80
100
120 Visits/100ARD Hospitalizations/10,000P&I Mortality/100,000
Rate
Age group
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Influenza Responsible for Substantial Disease
Deaths36,0001
Hospitalizations114,0002
Direct medical costs$1-$3 billion4
Infections and illnesses50–60 million3
Physician visits25 million3
1. Thompson WW et al. JAMA. 2003;289:179-186.2. CDC. MMWR Recomm Rep. 2003;58(RR-8):1-34.3. Couch RB. Ann Intern Med. 2000;133:992-998.4. Patriarca PA. JAMA. 1999;282:75-77.
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Seasonal
• In colder countries flu is largely seen during colder months and they vaccinate prior to this season (e.g. October)
• In tropical countries flu is seen all year round
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Flu Season in the Philippines Southern Hemisphere PatternCumulative Data: RITM Influenza Surveillance Data Feb. 1998 – Oct. 2004
AB
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Flu Season in the Philippines Southern Hemisphere PatternCumulative Data: RITM Influenza Surveillance Data Feb. 1998 – Oct. 2004
0
10
20
30
40
50
60
70
80
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
AB
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Influenza virus types
• Three : Influenza A, B, and C• Influenza types A or B viruses cause
epidemics; influenza A may cause pandemics
• Getting a flu shot can prevent illness from types A and B influenza but not from type C
• Influenza type C causes mild respiratory illness ; not thought to cause epidemics
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Influenza Virus: Segmented genome
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Influenza A virus divided into subtypes based on HA and N proteins on surface
• 15 HA, 9 N• Nomenclature based
on: site of origin isolate number year of isolation subtypeExample:influenzaA/
Johannesburg/33/94(H3N2)
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Drift or shift
• “Antigenic drift" - small changes in the virus that happen continually (influenza A and B)
• “Antigenic shift” - abrupt, major change in the influenza A viruses, resulting in new H &/or new H and N proteins that infect humans (influenza A only)
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Influenza subtypes in humans
• current subtypes of influenza A viruses found in people are A(H1N1) and A(H3N2)
• Influenza B virus is not divided into subtypes
• Influenza A(H1N1), A(H3N2), and influenza B strains are included in each year's influenza vaccine
• Protection is serotype specific
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Saturday, May 29, 2010
Domestic poultryDomestic pig:
Mixing vessel
Migratory water birds
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Domestic poultryDomestic pig:
Mixing vessel
Migratory water birds
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Avian Influenza
• Caused by 15 subtypes of influenza A virus subtype of avian influenza
• Low pathogenicity avian influenza (LPAI)
• Highly pathogenic avian influenza (HPAI) – First recognized in Italy in
1878– Extremely contagious in
birds – Rapidly fatal, high
mortality (almost 100% in a few days)
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Avian Influenza Infections in HumansConfirmed instances of avian influenza viruses infecting humans since 1997
• 1997: Hong Kong, avian influenza A (H5N1)• 1999: Hong Kong, avian influenza A(H9N2)• 2003: 2 cases of avian influenza A (H5N1)• 2003:H9N2 infection was confirmed in a child
in Hong Kong• 2003: Avian influenza A (H7N7) infections
among poultry workers / families in the Netherlands (> 80 cases )
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Characteristics of Avian Influenza Infections in Humans
• reported symptoms of avian influenza : typical influenza-like symptoms (e.g., fever, cough, sore throat and muscle aches) to eye infections, pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications
• It is believed that most cases of H5N1 infection in humans have resulted from contact with infected poultry or contaminated surfaces
CDC
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Current Avian Flu (H5N1) Strain
– genetically sequenced: all bird origin– antiviral resistance to amantadine and
rimantadine– oseltamavir and zanamivir should still be
effective
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Avian Influenza (Bird Flu) Outbreak Why H5N1 is of particular concern
• H5N1 mutates and acquires genes rapidly from other species
• Documented to cause severe disease in humans• avian influenza virus could change so that it could
infect humans and could spread easily from person to person
• no immune protection against them in the human population
• If an avian virus were able to infect people and gain the ability to spread easily from person to person, an “influenza pandemic” could begin
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Jets
4 days
Vaccines
Some antiviral drugs
60 million?
FLU PANDEMICS: THEN AND NOW
2005WHAT COULD HAPPEN
1 9 1 8WHAT HAPPENED
1.8 billion
Troop ships,railroad
4 months
Gauze masks,disinfectants
Bed rest,aspirin
20+ million
7 billion
Year
World Population
Primary mode of transportation
Preventive measures
Time for virus to circle the globe
Treatments
Estimated deadJanet Englund, MDPIDSP Feb. 2005
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Treatment of Influenza
• Antiviral Medications: – antiviral drugs: adamantanes: amantadine,
rimantadine neuraminidase inhibitors: zanamivir,
oseltamivir
– Antiviral treatment lasts for 3-5 days and must be started within the first 2 days of illness.
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Antiviral treatment and prophylaxis
• amantadine [4.4-8.8 mg/kg/day, not to exceed 150 mg/day] can be given for 3-5 days; for treatment of influenza A
• oseltamivir [2 mg/kg/dose BID] can be given for 5 days for treatment of influenza A and B.
Its use for treatment and prophylaxis of household contacts has been effective for children > 12 years old
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Saturday, May 29, 2010
Do I Need A Flu Shot?
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Target Groups For Vaccination
1. Those with increased risk of complications:
• Persons age 50 yrs old and above • Children from 6 to 23 months old• Adults and children with the following risk
factors:– Chronic cardiovascular disease (e.g. congestive
heart failure, Hypertensive cardiovascular disease, valvular heart disease, rheumatic heart disease, stroke)
– Chronic lung disease (e.g COPD, asthma, bronchiectasis, malignancies, chronic PTB)
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• Chronic metabolic disease (diabetes mellitus)• Chronic renal dysfunction• Hemoglobinopathies • Immunosuppressed (e.g.HIV, malignancies,
immunosuppressive drugs, radiation therapy, transplant patients)
• Children and adolescents who are receiving long-term aspirin therapy
• Residents of nursing homes and other chronic care facilities
• Pregnant women on their 2nd or 3rd trimester who have not received their flu vaccine within the last 12 months.
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Target Groups For Vaccination
2. Those who can transmit the disease to others
• Health care workers and other personnel of out patient care settings, hospitals, nursing homes, and chronic care facilities.
• Household contacts (including children) and caregivers of person at high risk.
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When Should You Give the Flu Shot?Highlights Influenza Consensus – Flu TWG Oct. 2004
• Data from the five-year epidemiologic data (February 1998 – September 2003) shows increased influenza activity June to November.
• Vaccination should be given once a year preferrably from February to June
• The Southern Hemisphere vaccine which is made available starting February of each year is recommended to cover the expected increase in influenza activity from June to November.
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Vaccine dosage by age group
Age Dose No. doses Route
6 – 35 mos 0.25 ml 1 or 2* IM
3 – 8 yrs 0.5 ml 1 or 2* IM
= or > 9 yrs
0.5 ml 1 IM
* 2 if receiving vaccine for 1st time, 1 month apart
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Thank You!
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