pan american health organization non-pharmacological interventions before a human influenza pandemic...

Pan AmericanHealthOrganization

Non-pharmacological interventions

before a human influenza

pandemic

Dr. Mónica GuardoPan American Health Organization - PAHO

Bogotá – April 20, 2006


Aspects Covered

• Definition – non-pharmacological interventions

• Characteristics of the transmission of influenza

• Review of the theoretical foundations of interventions to

control the spread from one country to another

• Theoretical foundation of the measures to reduce transmission

within each country, at a national and community level

• Past evidence, of the present and mathematical models

• Measures to reduce individual risk

• Recommendations and discussion


Non-Pharmacological Interventions

• Use of pharmacological measures against a pandemic:

– Vaccines and anti viral medicines

– Availability will not be enough

• 2005 – World Health Organization (WHO)

– Non-pharmacological public health interventions recommended for the

updated preparation plan

• 2006 – Experts Committee

– Emerging Infectious Diseases, Vol.12 (1) – January 2006, pg 81-94

– www.cdc.gov/eid

• Definition

– Interventions designed to reduce exposure in the people susceptible to

an infectious agent


Non-Pharmacological Interventions Fundamental Concepts

• Measures to limit international spread– Filtering and travel restrictions

• Measures to limit national and local spread– Isolation and treatment of the sick

– Vigilance and quarantine of those exposed

– Social distancing measures (like cancellation of reunions and

closing of schools)

• Measures to limit individual risk– Washing hands

– Use of masks in public

• Public communication of risks


• Symptomatic– adults - viral elimination 24-48 hours before symptoms

– Maximum infectiousness 24-72 hours of the disease – until day 5

– Symptomatic children – faster viral elimination and for a longer period

• Asymptomatic – related to a group of adults in New Zealand, 1991– 26 adults that packed fertilizer during 8 hours

– 16 with influenza type disease

– Initial case – malaise, without respiratory symptoms

• Influenza type disease six hours after finishing work

• Transmission by infected persons in an incubation period or those that show an asymptomatic infection

Sheat K. An investigation into an explosive outbreak of influenza - New Plymouth.Communicable Disease New Zealand 1992; 92:18-19.

Excretion and Viral Transmission


Forms of Transmission


• Transmission: person to person– Drops (particles >5µm in diameter): cough or sneeze

– Replication in epithelial cells of the respiratory ducts

• Other forms of transmission– Propagation through aerosol specially with a lack of ventilation

– By contact – contaminated hands, other surfaces or fomites

• Outbreak in a geriatric home in Hawaii– Transmission of oral secretions from one patient to another through a

professional without gloves• Environmental survival of influenza A

– Hard non porous surfaces (steel and plastic) up to 24-48 hours– Clothing, paper, fabric – up to 8 – 12 hours (35-40% humidity and 28ºC)– Major humidity less viral survival– Virus in non porous surfaces – passes to the hands for up to 24 hours– Virus in fabrics – passes to the hand up to 15 minutes

Forms of Transmission

Moser MR et al. An outbreak of influenza aboard a commercial airliner. Am J Epidemiol 1979;110:1-6.Alford RH et al. Human influenza resulting from aerosol inhalation. Proc Soc Exp Biol Med 1966;122(3):800-4.Morens DM, Rash VM. Lessons from a nursing home outbreak of influenza A. Infect Control Hosp Epidemiol 1995;16(5):275-80. Bean B et al. Survival of influenza viruses on environmental surfaces. J Infect Dis 1982;146(1):47-51.


Incubation and Viral Infectiousness

• Short period of incubation - 2 days (between 1 to 4 days)

• Symptoms 1-4 days post exposure

• Intervals between successive cases – between the appearance of the disease in two successive patients in the transmission chain (2 to 4 days)

• Viral excretion peak (maximum infectiousness) – initiation of the disease

• SARS comparison– Interval between successive cases 8 – 10 days

– Maximum infectiousness the second week of the disease

– Greatest time to implement isolation and quarantine measures

• Basic reproductive number (Ro)– Measure of secondary cases generated by an infected person (in a totally

susceptible population)

– 1918 Influenza (R0 = 1,8 a 3)

– Similar to SARS coronavirus (Ro = 2-4)


• International level

• National and local level

• Community level



Experiences from the Influenza Pandemic - 1918


Experiences from previous pandemicsPromulgated quarantine by islands

• October 1918, Australia– Quarantine in ships, with variable times

– Taking into consideration the date in which the most recent case appeared

– 7 days in ships in New Zealand and South Africa, independent of cases

– Taking of temperature at least once a day• Mouth temp ≥ 37,2ºC hospital isolation for observation

• October 1918 - May 1919– 79 “infected vessels”

• 2.795 patients, 48.072 passengers and 10.456 crew members

– 149 “non infected vessels”• 7.075 passengers and 7.941 crew members

– Without direct evidence of propagation from the vessel to the coast

• Notification of the pandemic’s arrival in Australia in January 1919

• Maritime quarantines delayed the entrance of influenza by 3 months

• Cumpston JHL. Influenza and maritime quarantine in Australia. Melbourne: Commonwealth of Australia. Quarantine Service. Service publication; 1919. Report No.: No. 18.• McQueen H. "Spanish 'flu",1919: political, medical and social aspects. Med J Aust 1975;1(18):565-70.


Effects and doubts about the quarantine in Australia, 1918

• Possible viral introduction before establishing quarantine– It could not be demonstrated

• Hiding of the disease by officials and soldiers of the marine that were returning to Australia in European vessels– To avoid prolonged quarantine

• Infection in Australia– The mortality rates were less than those of other places previously

affected


Experiences of previous pandemicsOther quarantine experiences

• African continent - 1918

– Quarantine in three port areas like Liberia, Gabón y Ghana

– Delay of entrance by several weeks, but less successful than in the

islands

– Disease arrived through interior routes

• Canada

– Drastic measures

• Police control points

• Interruption of road and train traffic

– They did not prevent or delay propagation among the provinces


Effect of quarantine in international frontiers – 1957 pandemic

• Israel – Delayed two months in comparison to neighboring countries

– Attributed to the absence of international travel with neighboring countries (due to political reasons, not quarantine).

• South Africa– Maritime restrictions resulted in “some delay”

• No effect in other areas

• Measures have to be severe in order for them to be efficient


SARS Experiences - 2003

Photo: Gavin Joynt

Photo: Gavin Joynt


Filtering the entrance of travelers arriving via air– SARS, 2003

4 countries in Asia and Canada

• Mechanisms for the measurement of body temperature

– 35 million travelers, detection 0 cases

• Health Questionnaire

– Travelers supplied information about their health, symptoms and exposure history

– 45 million travelers, detection of 4 cases

• Distribution of sanitary warning signs

– 31 million signs distributed to incoming travelers, limited information about the

follow up of those same ones


Filtering the entrance of travelers arriving via air– SARS, 2003

aBell DM. WHO Working Group on prevention of international and community transmission of SARS. Public health interventions and SARS spread, 2003. Emerg Infect Dis 2004;10:1900-1906.

bSt John RK et al. Border screening for SARS. Emerg Infect Dis 2005;11(1):6-10.

Continental China

• Distribution of 450,000 signs– Detection of 4 SARS cases possibly related to the signs

Thailand

• Distribution of 1 million signs– Detection of 24 cases with direct relation to said signs

Canada

• 5 people with SARS entered the country – none presented signs or symptoms at the international airports

• Filtering entrance, not a lot of sensibility and it was not cost -effective• Vigilance is preferable for the fast detection of imported casesb


Screening/Filtering passengers exiting via air – SARS, 2003

• March 27, 2003 Recommendation - WHO

– Exit filter for international passengers exiting via affected routes

– Transmission of SARS via air travel was not documented from countries that

implemented exit filters

• Reflection of the dissuasive effect on travelers and/or a low incidence of

SARS?

• Data combined from various countries indicated

– Detection of 1 case per 1.8 million exiting passengers that answered the health

questionnaire

– None, in the 7 million cases that subjected themselves to temperature

detection at the time of exit

Bell DM. WHO Working Group on prevention of international and community transmission of SARS. Public health interventions and SARS spread, 2003. Emerg Infect Dis 2004;10:1900-1906.


Estimate of the effect of screening/filtering entrance of travelers entering the United

Kingdom

• Mathematical modeling

• Considering filtering exit from countries with influenza pandemic

• 9% of asymptomatic persons would show signs during their trip to the UK at exit

• % greater if duration of flight greater– 17% (12-23%) in travelers from Asian cities

• 12, 000 airplane seats arriving from the Extreme Orient to the United Kingdom daily– 83% of those infected would not be detected

– Travelers arriving through connecting flights are not considered

Pitman RJ et al. Entry screening for SARS or influenza, policy evaluation. Br Med J 2005; http://bmj.bmjjournals.com/cgi/rapidpdf/bmj.38573.696100.3A


Recommendations from the WHO to contain international transmission

• Alert travelers that arrive in the country– Description of the symptoms and indications of where they should

inform if they suffer from these symptoms

• Consider filtering at exit– Health declaration and taking of temperature of international

passengers exiting the affected areas during phases 4 and 5

• Consider filtering arrival only when:– Exit filtering at boarding is below optimal

– Islands or geographically isolated areas

– Where the country’s internal vigilance capacity is limited


Advantages and disadvantages of exit filters

• Advantages– Smaller number of persons filtered– Greater number of positive prediction values– Reduction of transmission in flights and ships

• Disadvantages– Costly and problematic– It will not be totally efficient since the virus can be transmitted by

asymptomatic persons that will not be detected during the filter

• It is not recommended, during any phase, that countries quarantine themselves or that they close international frontiers.

• As it happened with SARS, non-pharmacological interventions centered principally at a national and community level and NOT international frontiers.


Recommendations for Travelers to H5N1 epizootic areas

Phase 3 Pandemic Alert

• Avoid:– Contact with farms– Contact with live animals in markets– Contact with surfaces that appear to be contaminated with

the fecal matter of chickens or other animals

• Diet:– Avoid local food prepared raw, with birds or their products– Only eat birds or their products that have been properly

cooked

• There are no recommendations for travel restrictions to affected countries



• International level

• National and local level

• Community level


Isolation of cases and contact quarantine - 1918

• Notification and obligatory isolation of cases in the community– They did not stop viral transmission and it was not very practical

• Canada, Alberta– Forced domiciliary isolation of cases – signs indicating “quarantine”

– They only detected 60% of the cases in the community• Difficulties diagnosing mild cases• Failure in the notification of cases to the authorities

• Australia, New South Wales– Obligatory notification – useful for identifying the first cases in a community

– No posterior value

• Military bases and university dorms in 1918– It did not stop the transmission but seemed to reduce the attack rates

– Especially if they were complemented with travel restrictions to and from the surrounding community


Isolation of cases and quarantine lesions of SARS, 2003

• Success of public campaigns for– Self recognition of the disease– Telephone consultation services with health information– Early isolation of patients seeking medical attention

• Inefficient Measures– Taking temperature of interurban travelers

• Efficient Measures– Isolation and quarantine in the community– Measures would be less effective before an influenza

pandemic


Social Distancing Measures• Avoid crowds

– To reduce the infectious peak of the epidemic, prolonged for several weeks

– 1957 Pandemic initially attacked military units, schools and other groups in close contact

– Incidence reduced in rural areas • Closing of schools and daycare centers

– In the Northern hemisphere the reinitiating of school activities after summer vacations

• It was important for initiating the main epidemic period– Influenza epidemics are amplified in primary schools

• However there is no evidence of the effectiveness of closing schools

– Epidemic in Israel, 2000• Teacher’s strike important reduction in the infection rates• Reinitiating of activities increased the rates


Simultaneous use of several strategiesHong Kong, SARS 2003

• Reduction of influenza and other respiratory diseases• Intervention

– Closing of schools, pools and other crowded areas

– Cancellation of sporting events

– Disinfecting taxis, buses and public areas

– Use of masks in public and frequent washing of hands

– Less social contact

• Use of masks in public - 76% of residents– With multiple measures

– There is no certainty of the contribution of the use of masks, if there was one1

– Studies carried out of control cases in Beijing and Hong Kong during SARS, 20032

– Use of masks in public was independently associated with protection towards SARS

– Dosis-response effect3

1. Lo JYC et al. Emerg Infect Dis 2005;11:1738-41. 2. Wu J et al. Emerg Infect Dis 2004;10(2):210-6.3. Lau JT et al. Emerg Infect Dis 2004;10(4):587-92.


Interim WHO RecommendationsPhases 4 and 5

• Fast detection and isolation of infected persons

• Detection of close contacts during the first 2 weeks of the disease

• Voluntary quarantine of those with symptoms during 1 week

• Use of antiviral medications for the treatment of cases and prophylaxis of other people in the initially affected area

• Entrance and exit restrictions for people in the area initially affected area in the country


Interim WHO RecommendationsPhase 6 – without affecting other countries

• Guidance for the sick – remain at home as soon as symptoms appear

• Warn caretakers – adequate precautions

• Non essential national trips to the affected areas must be postponed– If there are still significant areas in the country that have not

been affected

• People that have been knowingly exposed in a plane or large cruise ship– Consider daily fever controls between passengers and crew

members– Consider antiviral prophylactic treatment, if available


• Interruption of patient isolation, detection and quarantine of contacts– These measures will no longer be viable or useful

• Consider social distancing measures in the affected communities

• Repeatedly inform the population – Respect the need to wash hands frequently with soap and

water– Respect the need for “respiratory hygiene”

• Use of masks for the general population– Must not have noticeable repercussions over the transmission– Must be allowed, since its occurrence is likely to be

spontaneous

Interim WHO RecommendationsPhase 6 – pandemic, all affected countries


What can we do…as individuals? Interim WHO recommendations

• Diminishing the transmission of influenza– Wash hands

– Use masks based on risk

– Avoid contact of hands with nose and mouth and take care when coughing and sneezing

– Do not go to work while sick

– Use of masks during close contact with sick individuals

– Disinfect domestic surfaces contaminated with secretions

– Allow the systematic use of masks in public places, without promoting it

– Possible instructions for the use of masks in crowded places (public transportation)

• Without evidence support general disinfection of the environment/air

• Diminish the transmission of the bird flu A (H5N1)– Avoid contact with dead or sick birds

• Diminish the transmission of human influenza– Annual vaccine with the anti-influenza vaccine


Discarding of chickens potentially infected with H5N1 without protection

Thailand, February 2004

Photo: CDC


Guidance – Washing Hands

Fonte: OMS


Guidance for patients with a cough

• Respiratory hygiene and etiquette when coughing

• Cover your mouth when you cough and sneeze, avoid spitting

• Use handkerchiefs

• Meticulously dispose of handkerchiefs

• Wash hands after contact with respiratory secretions

• Sit at least 1 meter’s distance from other patients

Provide the patient

• Handkerchiefs

• Garbage cans that work without the use of hands

• Water, soap and alcohol

• Disposable towels to dry hands

pan american health organization non-pharmacological interventions before a human influenza pandemic...

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