health talk on bird flu for airport community 21 october 2005 s peaker: dr john simon
TRANSCRIPT
Health Talk on Bird Flu for Airport Community
21 October 2005
Speaker: Dr John Simon
What’s All The Fuss About Bird Flu?
John SimonHonorary Professor
Dept. of Microbiology
University of Hong Kong
Avian influenza H5N1
“The Enemy”
Neuraminidase HaemagglutininBirds N 1-9 H 1-16Human N1-2 H1-3
Human influenza epidemics
Influenza Pandemics in the 20th Century
• In 1957 ‘Asian’ influenza caused more than 1 million deaths
• In 1968 ‘Hong Kong’ influenza caused more than 1 million deaths
• In 1918 ‘Spanish’ influenza caused
40 million deaths
Influenza Pandemics in the 20th Century
A Pandemic today is likely to:• Spread rapidly• Affect 15-30% of the population of any one
country within weeks• Span the globe in months (like 1968 pandemic)• Have greater socio-economic impact• Impact supply chains• Not be stopped the way that SARS was.
Bird Flu
• Due to a Type A Influenza
• H5N1, H9N2, H7N7, H5N2, H7N1
• H5N1: ‘Highly Pathogenic Avian Influenza’
H5N1 In Poultry
• South Africa 1961
• Hong Kong 1997
• China, South Korea, Japan, Vietnam, Thailand, Camodia, Laos, Pakistan, Indonesia, Malaysia 2003-2004
• Kazakhstan, Russia (Urals, Siberia) Mongolia, Romania, Turkey 2005
H5N1 in Wild Birds
• Wild Ducks Have No Symptoms
• Asymptomatic Carriers
• Bird-fall in Qinghai
• Migratory Birds Spread It
• Now a Zoonosis
We Had Our Chance
• Culling Stopped It In HK in 1997
• Universal Culling in Vietnam, Thailand & China May Have Stopped It
• Now It Is A Zoonosis It Is Here to Stay
Surveillance of H5N1 viruses in live poultry markets in mainland China
Li et al Nature 2004; 430: 209-213
• I Don’t Know What Will Happen Except To Tell You “We’re Screwed”– Dr Michael Osterholm, Director Center for ID
Research & Policy June 2005.
Human H5N1 cases and deaths since Jan 2004
Cases DeathsVietnam 91 41Thailand 17 12Cambodia 4 4Indonesia 5 3Total 117 60
The tip of the iceberg
Features of H5N1 in Humans
• Male/Female Ratio 2/3
• Age Range 4 Months to 69
• Median Age 19. Average Age 24
• Case Fatality Rate (CFR) 52%
• CFR Last 10 Months 39%
Transmission To Humans
• Nasal, Salivary & Fecal Excretions
• Contact With Contaminated Surfaces
• Inhalation of Dried Out Feces
• Eating Undercooked Viremic Birds
• Drinking Ducks’ Blood
Human-To-Human Transmission
• Currently Inefficient
• Only One Likely Case (Thailand 2003)
• Requires Very Close Contact
• Efficent Transmission Pandemic
• Requires Virus Mutation
The origin of influenza pandemics
How may a H5N1 pandemic virus arise?
It happened with SARS
It happened with the 1918 “Spanish flu”
Will A Pandemic Occur?
• Yes: As They Have Occurred Over Many Centuries Past
• Can’t Say When: Next Month, Next Year?
• Can’t Say If It Will Be H5N1 or Another
Why it is likely that H5N1 will be the
next pandemic virus?
• Endemic across a wide geographical area
• Repeated (thousands) opportunities for infecting humans
• Repeated inter-species transmission to mammals and to humans
• Potential for reassortment in pigs or in humans
So What’s The Fuss
• A pandemic virus could be due to recombination (reassortment) or gradual mutation with a direct jump from birds to humans. The latter is likely to be more severe than the former
• H5N1 mutation allowing efficient human-to-human transmission may not be less severe a clinical illness in humans than it currently is and might parallel the severity seen in the 1918 pandemic
Incubation
• Unknown. Probably Less Than 1 Week
• “Ordinary Flu” 1-4 Days
Clinical Course
• “Ordinary Flu”: Fever, Cough, Muscle Pain, Headache, Sore Throat
• “Cytokine Storm”
• Pneumonia, Respiratory Distress
• Multi-organ Failure, DIC
Treatment
• Supportive Therapy
• Mechanical Ventilators
• Antiviral Drugs (Relenza or Tamiflu)
• Relenza: Inhalation. More difficult to use but as effective as Tamiflu
Tamiflu
• Must start within first 48 hours
• Preferably within first 24 hours
• Dose 1 capsule (75mg) twice daily 5 days
• Suspension form available for children
• Active against all types of influenza A
• Some partial resistance H5N1 noted
• No guarantee it will be effective !
Tamiflu as a Prophylaxis
• 1 Capsule Daily for– Contacts of known cases– Those involved in culling– In pandemic situations? How long
Tamiflu
• Not available: Indonesia, India, Pakistan
• Cost for a packet of 10 capsules varies
• US$25-60
Vaccine
• Sanofi-pasteur trials successful
• Probably ineffective against mutant
• Will need to rapidly make new vaccine
• However current process is very slow
• Will take 6 months to develop
• You are unlikely to get the vaccine
• Slow to make. Only small quantities
Effects of a Pandemic
• Total disruption of travel and business
• International borders will close
• Schools, cinemas, restaurants close
• Hospitals cannot cope
• Shortage of ventilators
• Up to ?? 50 million may die
• Friends, colleagues, family will die
What Needs to be Done?
• Control the outbreak in poultry
• Early warning of human-to-human spread
• Pandemic preparedness and logistics
• Antivirals
• Vaccines: logistics of production
Problems with Control in Poultry
Backyard flocks
Problems with Control in Poultry
“wandering ducks” and “Trojan horses”
Problems with Control in Poultry
Live poultry markets
Can We Stop A Pandemic
• Theoretically Yes (“Nature”, “Science”)
• Need to Identify Early Clusters
• Social Isolation
• Blanket Tamiflu
• Reduce Ro
• In My Opinion “No!”
So What Shall We Do?
• Prepare for a Pandemic
• Governments to Stockpile Tamiflu
• Individuals to Purchase Own Supplies
• Corporations to Make Contingencies
• Get “Ordinary Flu” Vaccination
• Educate
Transmission of influenza viruses
5
• Infectious from 24-48 hrs before symptoms• Infectious until 7-8 days after onset of disease, or longer• Asymptomatic infection may transmit
Large droplets: short range?? Aerosols: long range
Contaminated hands?Surfaces?
Possible interventions:
• Hand hygiene: facilities available in workplace • Masks
– Recommended for those with symptoms– For those in “person-contact” occupations– Education on how to use and dispose of a mask. – Doubtful benefit for general community
• ‘Increase “social distance”– Closure of schools and public places– Stop public gathering – Curtailing non-essential activities and services– Curtail non-essential domestic travel
Reduction of other viral respiratory infections during SARS
Websites
• www.cdc.gov/flu/avian/index.htm
• www.who.int/csr/disease/avian_influenza/en/
• www.info.gov.hk/dh/diseases/influenza/influenza.htm
• www.wpro.who.int/avian/
Summary
• An H5N1 Pandemic Will Occur
• Many Millions Will Die
• Do Not Expect To Get A Vaccine
• Tamiflu or Relenza May Work. Get It Now!
Oh! It’s just the flu
Acknowledgment
• Professor Malik PeirisUniversity of Hong Kongfor use of some of his slides
Response MeasuresAlert Response
LevelSerious
Response LevelEmergency
Response LevelOwner
Influenza vaccination See Notes * HRD
Temperature screening, health declaration TBU
Staff education HRD / SSEPS / CS
Airport staff temperature monitoring All BU / SU
Encourage restaurants to provide serving utensils RAB
Maintain close contact with Department of Health SSEPS / TBU
Maintain an adequate supply of personal protection equipment, i.e. face masks, disinfectants, etc
HRD/TSP
Step up cleaning and disinfection of public installations TBU
Provide adequate facilities and cleaning materials for hand-washing
TBU
Case Reporting All BU / SU
Step up maintenance on indoor ventilation system TSP
Adequate equipment for protecting frontline staff TSP
Restrict Access to Critical Operational Control Centers TBU / ABU / TSP / MIT
Staggered work deployment TBU / ABU / TSP / MIT
Minimize large meetings All BU / SU*To lower the possibility of misdiagnosing cold and flu with avian flu