Influenza a h1 ni latest

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  • 1.Just-in-Time LectureInfluenza A(H1N1) (Swine Flu): A Global Outbreak (Version 11, first JIT lecture issued April 26)Tuesday, May 26, 2009 (01:30 AM EST)
    Rashid A. Chotani, MD, MPH, DTM
    Adjunct Assistant Professor
    Uniformed Services University of the Health Sciences (USUHS)


  • RNA, enveloped

3. Viral family: Orthomyxoviridae 4. Size: 80-200nm or .08 0.12 m (micron) in diameter

  • Three types

5. A, B, C 6. Surface antigens 7. H (haemaglutinin) 8. N (neuraminidase)Virus
Credit: L. Stammard, 1995
9. 10. Structure of the influenza hemagglutinin monomer
HA monomer.Sites A-E are immunodominant epitopes (From Fields Virology, 2nd ed, Fields & Knipe, eds, Raven Press, 1990, Fig.40-4)
11. Structure of the influenza hemagglutinin trimer
HA trimer. (From Fields Virology, 2nd ed, Fields & Knipe, eds, Raven Press, 1990, Fig.39-6)
12. Influenza A reservoir
Wild aquatic birds are the main reservoir of influenza A viruses.Virus transmission has been reported from weild waterfowl to poultry, sea mammals, pigs, horses, and humans.Viruses are also transmitted between pigs and humans, and from poultry to humans.Equine influenza viruses have recently been transmitted to dogs. (From Fields Vriology (2007) 5th edition, Knipe, DM & Howley, PM, eds, Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia, Fig 48.1)
13. Influenza replication
Replication of influenza A virus. After binding (1) to sialic acid-containing receptors, influenza is endocytosed and fuses (2) with the vesicle membrane. Unlike for most other RNA viruses, transcription (3) and replication (5) of the genome occur in the nucleus. Viral proteins are synthesized (4), helical nucleocapsid segments form and associate (6) with the M1 protein-lined membranes containing M2 and the HA and NA glycoproteins. The virus buds (7) from the plasma membrane with 11 nucleocapsid segments. (-), Negative sense; (+), positive sense; ER, endoplasmic reticulum. (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Figure 60-2.)
14. Influenza pathogenesis
Pathogenesis of influenza A virus. The symptoms of influenza are caused by viral pathologic and immunopathologic effects, but the infection may promote secondary bacterial infection. CNS, Central nervous system. (From Medical Microbiology, 5th ed., Murray, Rosenthal & Pfaller, Mosby Inc., 2005, Figure 60-3.)
15. Definitions
Epidemic a located cluster of cases
Pandemic worldwide epidemic
Antigenic drift
Changes in proteins by genetic point mutation & selection
Ongoing and basis for change in vaccine each year
Antigenic shift
Changes in proteins through genetic reassortment
Produces different viruses not covered by annual vaccine
16. Survival of Influenza Virus Surfaces and Affect of Humidity & Temperature*
Hard non-porous surfaces 24-48 hours
Plastic, stainless steel
Recoverable for > 24 hours
Transferable to hands up to 24 hours
Cloth, paper & tissue
Recoverable for 8-12 hours
Transferable to hands 15 minutes
Viable on hands 200,000 Hospitalizations
$37.5 billion in economic cost (influenza & pneumonia)
>$10 billion in lost productivity
Pandemic Influenza
An ever present threat
18. Swine Influenza A(H1N1)Introduction
Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza that regularly cause outbreaks of influenza among pigs
Most commonly, human cases of swine flu happen in people who are around pigs
Swine flu viruses do not normally infect humans, however, human infections with swine flu do occur, and cases of human-to-human spread of swine flu viruses have been documented
19. Swine Influenza A(H1N1) History in US
A swine flu outbreak in Fort Dix, New Jersey, USA occurred in 1976 that caused more than 200 cases with serious illness in several people and one death
More than 40 million people were vaccinated
However, the program was stopped short after over 500 cases of Guillain-Barre syndrome, a severe paralyzing nerve disease, were reported
30 people died as a direct result of the vaccination
In September 1988, a previously healthy 32-year-old pregnant woman in Wisconsin was hospitalized for pneumonia after being infected with swine flu and died 8 days later.
From December 2005 through February 2009, a total of 12 human infections with swine influenza were reported from 10 states in the United States
20. Swine Influenza A(H1N1) Transmission to Humans
Through contact with infected pigs or environments contaminated with swine flu viruses
Through contact with a person with swine flu
Human-to-human spread of swine flu has been documented also and is thought to occur in the same way as seasonal flu, through coughing or sneezing of infected people
21. Swine Influenza A(H1N1) Transmission Through Species
Human Virus
Avian Virus
Reassorted Virus
Swine Virus
Reassortment in Pigs
22. Swine Influenza A(H1N1) March 2009Timeline
In March and early April 2009, Mexico experienced outbreaks of respiratory illness and increased reports of patients with influenza-like illness (ILI) in several areas of the country
April 12, the General Directorate of Epidemiology (DGE) reported an outbreak of ILI in a small community in the state of Veracruz to the Pan American Health Organization (PAHO) in accordance with International Health Regulations
April 17, a case of atypical pneumonia in Oaxaca State prompted enhanced surveillance throughout Mexico
April 23, several cases of severe respiratory illness laboratory confirmed as influenza A(H1N1) virus infection were communicated to the PAHO
Sequence analysis revealed that the patients were infected with the same strain detected in 2 children residing in California
Samples from the Mexico outbreak match swine influenza isolates from patients in the United States
Source: CDC
23. Swine Influenza A(H1N1) March 2009Facts
Virus described as a new subtype of A/H1N1 not previously detected in swine or humans
CDC determines that this virus is contagious and is spreading from human to human
The virus contains gene segments from 4 different influenza types:
North American swine
North American avian
North American human and
Eurasian swine
24. Swine Influenza A(H1N1) US Response
The Strategic National Stockpile (SNS) is releasing one-quarter of its
Anti-viral drugs
Personal protective equipment and
Reparatory protection devices
President Obama today asked Congress for an additional $1.5 billion to fight the swine flu
On April 27, 2009, the CDC issued a travel advisory that recommends against all non-essential travel to Mexico
Source: CDC
25. Swine Influenza A(H1N1) Global Response
The WHO raised the alert level to Phase 5
WHOs alert system was revised after Avian influenza began to spread in 2004, and April 27 was the first time it was raised above Phase 3 and on April 29 to Phase 5.
European Union (EU) issued a travel advisory to the 27 EU member countries recommending that non-essential travel to affected parts of the U.S. and Mexico be suspended
Source: WHO
26. Swine Influenza A(H1N1) May 25, 2009Status Update
MEXICO: March 01-May 22, a total of
4,174 Laboratory confirmed cases, with 80 deaths and 1311 hospitalizations (for pneumonia) reported in 32 of 32 States
UNITED STATES: March 28-May 25, a total of
6,764 Laboratory confirmed cases, with 10 deaths(Arizona 3; Missouri 1; New York 1; Texas 3; Utah 1 and; Washington 1) from 48 States (including District of Columbia)
Over 100 Hospitalizations
Most cases mild
CANADA:As of May 25, a total of
921 Laboratory confirmed cases, with one deaths (1 Alberta) from 10 of 13 States
116 new Laboratory confirmed casesMay 25
Most cases mild
Source: Secretaria de Salud, Mexico, CDC, Public Health Agency of Canada, European CDC, WHO
27. Swine Influenza A(H1N1) May 25, 2009Status Update
EUROPEAN UNION & EFTA COUNTRIES: April 27- May 25, a total of
360 Laboratory confirmed cases, with no deaths from 19 countries
11 confirmed cases reported on May 24
130 in-country transmissions
Vast majority of cases reported between 20-49 years of age
Most cases (except 1) report mild disease
GLOBALLY: March 1-May 25, a total of
12,727 Laboratory confirmed cases, from 46 countries
92 Deaths among laboratory confirmed cases from 4 countries
Mexico: 80 deaths
US: 10 deaths
Canada: 01 death
Costa Rica: 01 death
Source: Secretaria de Salud, Mexico, CDC, Public Health Agency of Canada, European CDC, WHO
28. Swine Influenza A(H1N1)MMRW Report, April 28
MMWR, April 28, 2009 / 58(Dispatch);1-3
47 patients reported to CDC with known ages (out of 64) the median age was 16 years (range: 3-81 years)
38 (81%) were aged