Influenza (Pandemic)Influenza (Pandemic)

Dr Roger Gajraj

Consultant in Communicable Disease Control

HPA West Midlands EastBartholomew House142 Hagley RoadBirmingham B16 9PATel: 0121 224 4670

April 2008April 2008

Influenza

Avian influenza

Seasonal influenza

Pandemic influenza

– How, when and where

– Impact

– Spread

– Control

• Public health measures

• Workplace considerations

• Actions for individuals

Outline

Epidemic: serious outbreak in a single

area

Pandemic: epidemic spreading around

the world affecting hundreds of

thousands of people, across many

countries

Definitions

Influenza

Haemagluttinin H Protein

Enables virus to attach to host cell

15 exist in nature

H1, H2, H3: human infection

H5, H7, H9

Influenza Virus

Neuraminidase N Protein

Enables new virion release from host cell

Essential for virus replication

N1, N2: human infection

Humans only

Humans only

Humans

Birds

Mammals

Hosts

Sporadic mild illnessC

Epidemics infrequentlyB

Epidemics

PandemicsA

Disease patternsType

Influenza disease patterns

Avian influenza(“bird flu”)

Avian influenza

A disease of birds: wild and domestic

Bird saliva, nasal fluids, droppings, feathers

H5N1

• Severe

• Chickens, ducks, wild birds

• Many countries

‘Human’ avian influenza

Very small number of humans affected

- Local people with close contact with infected birds

Does NOT spread easily person-person

- Few instances where very close person-person contact may have resulted in transmission

- Person-person-STOP

No evidence of widespread asymptomatic infection

Avian influenza symptoms

Similar to ordinary flu: sudden onset

Fever (temperature of 38°C or more)

Cough

Shortness of breath

Headache

Sore throat

Sore eyes

Muscle aches

Seasonal influenza

Signs and symptoms

Abrupt onset, Fever, Cough/SOB

Also:

Malaise, Chills, Headache, Loss of appetite, Runny nose, Sneezing, Muscle aches, Sore throat

No symptoms in 50%?

Severe complications and death

Bacterial &/or viral pneumonia

Overwhelming viraemia

Annual influenza vaccine

Winter; 12,000 deaths annually

Vaccine: two A strains and one B strain

Risk groups

- Elderly (over 65s)

- Chronic illness: asthma, bronchitis, diabetes, heart, kidney,

liver, weak immunity

- Nursing and residential homes

- Carers

- Health and social care workers

Pandemic influenzahow, why, when, where?

Antigenic change

Enables influenza A viruses to cause epidemics and

pandemics

Influenza A virus surface antigens undergo frequent

changes

Minor changes - antigenic drift

Major changes - antigenic shift

Antigenic drift

New variants of prevailing strains emerge every

year

Result in seasonal flu each winter

Some years are worse than others – partly related

to degree of ‘drift’

Antigenic shift

Influenza A only

Major changes in the surface antigens

Occurs in 2 ways:

- Sudden ‘adaptive’ change during replication

- Genetic exchange (‘re-assortment’) between human & animal strains

Population will have little or no immunity to new virus from

previous exposure or vaccination

Lack of immunity allows virus to spread more rapidly and

more widely

New pandemic strain

Avian strain and Human strain

• Genetic reassortment

Human strain

• Abrupt major genetic change

Avian strain

• Adaptation in humans

Migratory water birds

New influenza strain (1)

Domestic bird

Migratory water birds Domestic

bird

New influenza strain (1)

New influenza strain (2)

New influenza strain (2)

Migratory water birds

New influenza strain (3)

Domestic bird

Migratory water birds

New influenza strain (3)

Pre-requisites for pandemic influenza

• New influenza A sub-type

• Little or no pre-existing population immunity

• Causes significant clinical illness

• Efficient person-to-person spread

H5N1

End of pandemic. Return to inter-pandemic period

Post Pandemic Period

UK Alert level1 Virus/cases only outside the UK2 Virus isolated in the UK3 Outbreak(s) in the UK4 Widespread activity across the UK

Increased and sustained transmission in general population

6

Pandemic Period

Large cluster(s) but human-to-human spread still localised

5

Small cluster(s) with limited and highly localised human-to-human transmission

4

UK not affectedUK has strong travel/trade with affected countryUK affected

Human infection(s) with a new subtype, but only rare spread to a close contact

3

Pandemic Alert Period

Animal influenza virus subtype poses substantial risk

2

UK not affectedUK has strong travel/trade with affected countryUK affected

No new influenza virus subtypes detected in humans

1

Inter-pandemic Period

Significance for the UKInternational phases

End of pandemic. Return to inter-pandemic period

Post Pandemic Period

UK Alert level1 Virus/cases only outside the UK2 Virus isolated in the UK3 Outbreak(s) in the UK4 Widespread activity across the UK

Increased and sustained transmission in general population

6

Pandemic Period

Large cluster(s) but human-to-human spread still localised

5

Small cluster(s) with limited and highly localised human-to-human transmission

4

UK not affectedUK has strong travel/trade with affected countryUK affected

Human infection(s) with a new subtype, but only rare spread to a close contact

3

Pandemic Alert Period

Animal influenza virus subtype poses substantial risk

2

UK not affectedUK has strong travel/trade with affected countryUK affected

No new influenza virus subtypes detected in humans

1

Inter-pandemic Period

Significance for the UKInternational phases

End of pandemic. Return to inter-pandemic period

Post Pandemic Period

UK Alert level1 Virus/cases only outside the UK2 Virus isolated in the UK3 Outbreak(s) in the UK4 Widespread activity across the UK

Increased and sustained transmission in general population

6

Pandemic Period

Large cluster(s) but human-to-human spread still localised

5

Small cluster(s) with limited and highly localised human-to-human transmission

4

UK not affectedUK has strong travel/trade with affected countryUK affected

Human infection(s) with a new subtype, but only rare spread to a close contact

3

Pandemic Alert Period

Animal influenza virus subtype poses substantial risk

2

UK not affectedUK has strong travel/trade with affected countryUK affected

No new influenza virus subtypes detected in humans

1

Inter-pandemic Period

Significance for the UKInternational phases

End of pandemic. Return to inter-pandemic period

Post Pandemic Period

UK Alert level1 Virus/cases only outside the UK2 Virus isolated in the UK3 Outbreak(s) in the UK4 Widespread activity across the UK

Increased and sustained transmission in general population

6

Pandemic Period

Large cluster(s) but human-to-human spread still localised

5

Small cluster(s) with limited and highly localised human-to-human transmission

4

UK not affectedUK has strong travel/trade with affected countryUK affected

Human infection(s) with a new subtype, but only rare spread to a close contact

3

Pandemic Alert Period

Animal influenza virus subtype poses substantial risk

2

UK not affectedUK has strong travel/trade with affected countryUK affected

No new influenza virus subtypes detected in humans

1

Inter-pandemic Period

Significance for the UKInternational phases

Warning signs!

WHO experts believe signs of another pandemic are

increasing

Rapid and continuing spread of H5N1 avian influenza,

outbreaks occurring at the same time in several

countries, historically unprecedented

Linked to human cases of Avian H5N1 flu

The virus may be adapting to infect people more readily

History of Influenza

412 BC: first mentioned by Hippocrates

1580: first pandemic described

1580 – 1900: 28 pandemics

What do we know about pandemic influenza

Geographic spread: 1968-69 Hong Kong pandemic

07/68

08/68

09/68

09/68

09/68

09/68

06/69

09/68

01/69

C.W. Potter, Textbook of Influenza, 1998

AsiaEurope

Africa

Australia

South

America

North

America

1918/19 H1N1

- 3 distinct waves: spring 1918; autumn 1918; winter 1919

- 2nd wave the largest and highest case fatality

1957/58 H2N2

- 2nd wave very small compared to 1st

1968/69/70 H3N2

- 1st wave winter 1968/69

- 2nd wave 1969/70 more severe

Pandemic waves

0

20

40

60

80

100

120

140

160

0-4

5-9

10-1

4

15-1

9

20-2

4

25-2

9

30-3

4

35-3

9

40-4

4

45-4

9

50-5

4

55-5

9

60-6

4

65-6

9

70-7

4

75-7

9

80-8

4

85+

Dea

th R

ate

per

1,0

00

4st quarter

1st quarter

Age specific influenza death rates among females in England & Wales during 1st and 4th quarters of 1918

Ministry of Health, GB, 1919

Estimating health impact &effectiveness of interventions

UNPREDICATABILITY the key lesson

Role of modelling

to estimate possible range of effects

to suggest which responses are robust over the range of uncertainty

Modelling

data fed into the models

assumptions made in the model design

Pandemic flu modelling

little data

wide range of plausible assumptions

Pandemic influenzaIMPACT

Planning assumptions (1)

Pandemic highly probable

Could occur at any time in the future

Could occur at any time of the year

Likely origin: SE Asia, Middle East or Africa

Spread to the UK in 2-4 weeks

Further 1-2 weeks until widespread UK activity

One or more waves; initial wave 3-5 months

Subsequent waves weeks or months apart

Subsequent waves possibly more severe than first

Planning assumptions (2): impact

All ages likely to be affected

Children and fit adults may be greater risk

Cases absent from work for up to 10 days

Reasonable worst case:

- 50% clinical attack rate (22% in peak week)

- 30% will need GP care

- 4% will require hospitalisation (25% of these to ITU)

- average hospitalisation for 6 days (10 days for ITU)

- 2.5% case mortality

What an influenza pandemic will mean for the UK

High levels of illness

Intense pressure on health services

Disruption to many aspects of daily life

Many deaths

Impact: University of Birmingham

Population of students and staff: 32,000

16,000 cases

9,120 need GP care

640 hospitalised cases

400 deaths

Deaths from seasonal, avian, & pandemic influenza

Previous pandemics (E&W)

1918/19 (H1N1; ‘Spanish flu’): 198,000

1957/58 (H2N2; ‘Asian flu’): 37,500

1968/69/70 (H3N2; ‘Hong Kong flu’): 78,000

Seasonal flu (E&W)

Annual: 12,000

1989/90: 26,000

Avian influenza (World)

1995 (UK; H7N7): 0 (1)

1997 (Hong Kong; H5N1): 6 (18)

1998 (China; H9N2) : 0 (5)

1999 (Hong Kong; H9N2) : 0 (2)

2003 (Hong Kong; H5N1): 1 (2)

2003 (Canada; H7N3): 0 (2)

2003 (Holland; H7N7) : 1 (84)

2003 (Hong Kong; H9N2) : 0 (1)

From 2003 (E/SE Asia; H5N1) : 238 (378) 03/04/08

Next pandemic (UK)

Worst case: 750,000 ?

Pandemic influenzaSPREAD

Incubation period: 1-4 days

Infectious period

- 5 days from onset

- 7 days in children

Asymptomatic people can spread infection

Highly transmissable: R0 1.4-1.8

Transmission

Large droplets fall

on people, surfaces,

bed, clothes

Courtesy of CDC

Mode of spread

- Direct: droplet spread

- Indirect: contact with

contaminated surfaces

- Airborne

Transmission (2)

Virus survivalHard surfaces:

Detectable up to 72hr

Viable quantities transferable and detectable on hands: 24hr

Soft surfaces/furnishings:

Detectable up to 24hr

Viable quantities transferable & detectable on hands: 15mins

Survival on hands after transfer: 5 minutes

Easily inactivated on surfaces:

Household cleaners, bleach solutions, standard detergents

Easily inactivated on hands:

Soap, water and drying

OR alcohol based gels/solutions (30 sec)

Ref: Guidance for cleaners

Pandemic influenzaCONTROL/ PUBLIC HEALTH MEASURES

Principles of pandemic response

Business continuity

Health care

Responding to many deaths

Communicable disease control

- on an epidemic scale

Supporting health services

- eg social care and policing

Activities to support the above

- eg surveillance, HR policies

Options for population-wide interventions

Pre-pandemic vaccine

Schools closures

Travel restrictions

Action at UK ports

Restrictions of mass public gatherings

Cases: home isolation; hygiene; infection control

Wearing of masks by the public

Antivirals; pandemic-specific vaccine

Antiviral drugs

UK stockpile of 14.6 million courses

Likely the only early available medical countermeasure

Prevent flu virus from reproducing

Effective if course started within 48 hours

National Flu Line service

Predominantly for treatment (not prevention)

- If available stock < number of cases, treat priority groups

Antiviral drugs (2)

NOT a ‘magic bullet’

- Shorten the illness by one day

- Reduce severity of symptoms

Treating all cases in a pandemic might

- Decrease attack rate by one third?

- Reduce hospitalisations by ~50%?

- Decrease number of deaths

BUT: Unknown if it will be effective vs pandemic strain

Is there a vaccine?Likely to be the most effective intervention against influenza

New virus therefore no vaccine

- ‘Ordinary’ flu vaccine or past flu jab: no protection

Vaccine cannot be made until virus identified

- Will not be available in early stages

- 4-6 months to produce, possibly longer

Initial available vaccine will be given to nationally agreed

priority groups

Ongoing work/ research to reduce production time

Aim: immunise whole population

Pandemic influenzaWORKPLACE CONSIDERATIONS

“Business as usual, for as long and as far

as that is possible”. Pandemic flu. A national

framework for responding to an influenza pandemic. DH,

Cabinet Office. Nov 2007

Absenteeism

Personal illness

Carer responsibilities

- Caring for ill relatives

- School closures

Bereavement

Fear of infection

Other factors

- eg transport disruption

Absenteeism (2)

Personal illness: absent from work up to 10 days

50% workforce might require 7-10 days off work sometime

Staff absenteeism will reflect pandemic profile

- Peak absenteeism lasting 2-3 weeks

- 15-20% absenteeism at the peak

- 30-35% absenteeism at the peak for small teams/

organisations (5-15 staff)

Estimating staff absence levels

- Proportion of staff with childcare or carer responsibilities

- ‘Normal’ absence levels

Health and Safety at Work

The Law

- Health and Safety at Work etc Act 1974

- Management of Health and Safety at Work Regulations 1999

- Control of Substances Hazardous to Health Regulations (COSHH)

Scenarios

- Exposure as a direct consequence of work (eg research; HCW;

cleaners; etc)

- Indirect Health and Safety considerations (eg staff redployment;

lone/ home working; etc)

Health and Safety at Work (2)

Local risk assessments

- Opportunity to educate and reassure

- Joint assessments: employers, employees, trade unions

- Risk of greater exposure than in the community?

- Vulnerable staff at particular risk

- Proportionate containment and protection measures

Health and Safety at Work (3)

Changes to working arrangements

- eg flexible hours; working from home

- staff redeployment to unfamiliar tasks: training

- Working Time Regulations 1998

Infection control considerations

- eg reduce close contact; physical barriers; enhanced

cleaning; hygiene facilities; PPE

Health and Safety at Work (4)

Employees who develop symptoms at work

- face mask; go home; avoid public transport

Employees who call in sick

- stay at home; reassure; follow-up contact

Make best use of recovered staff

Closure of educational facilities

Schools and early years/childcare settings

- Depending on pandemic impact, Govt may advise closure

- Closure from arrival of the first confirmed cases in the

LRF area, until the local epidemic is over

Further and higher education

- No Govt plans to advise closure

- Each institution to decide how it operates: based on risk

assessment and individual circumstances

Pandemic influenzaACTIONS FOR INDIVIDUALS

If you do catch the flu

Stay at home and rest

Symptomatic relief

- aspirin, ibuprofen, paracetamol

- follow the instructions

- under 16 yr: no aspirin

- under 2 yr: many cough and cold medicines dangerous

Drink plenty of fluids

Wear a disposable face mask if it is absolutely essential

to go out (eg to go to hospital)

Protect yourself and others

Cover nose and mouth with a tissue when coughing or sneezing

Dispose of dirty tissues promptly & carefully – bag and bin them

Wash hands frequently with soap & warm water to reduce virus

spread from hands to face or other people, especially

after blowing nose or disposing of tissues

Clean frequently touched hard surfaces (eg kitchen worktops,

door handles) regularly using normal cleaning products

Avoid crowded gatherings where possible, especially in

enclosed spaces

Make sure that children follow this advice

END