preparing for microbial threats to health: what every professional should know

Preparing for Microbial Threats to Health:What Every Professional Should Know

Tomas J. Aragon, MD, DrPH

Health Officer, City & County of San FranciscoDirector, Population Health Division (PHD), SFDPH

June 9, 2014

Tomas J. Aragon, MD, DrPH (SFDPH) Preparing for Microbial Threats to Health June 9, 2014 1 / 33

Acknowledgments

Robert S. Nakao, Executive Publisher, Advantage Business Media

SFDPH Population Health Division leadership and staff

Association of Bay Area Health Officials (ABAHO)

California Conference of Local Health Officers (CCLHO)

Center for Infectious Disease & Emergency Readiness*

Cal PREPARE Systems Research Center*

California Department of Public Health (CDPH)

National Association of County & City Health Officials (NACCHO)

Centers for Disease Control and Prevention (CDC)

* UC Berkeley School of Public Health


Contagion—The movie! vs. Contagion—Your reality!

Glass RJ, et al. Targeted social distancingdesign for pandemic influenza. Emerg InfectDis. 2006 Nov;12(11):1671-81. PubMed:17283616.


Middle East Respiratory Syndrome (MERS), June, 2014

Deadly Virus’s Spread Raises Alarms in Mideast: SaudisDefend Approach to MERS Outbreak, Even as CasesIncrease. Wall Street Journal Online, April 13, 2014 Saudi Ministry of Health, June 7, 2014


Overview

1 Challenge of complexity

2 Controlling microbial threatsTransmission mechanismsTransmission dynamicsTransmission containment

3 Integrated model for controlling microbial threats


Well established cause of outbreaks!


Well established response to outbreaks!


Challenge of complexity

SFDPH PHD Controlling Infectious Diseases (CID) ModelAddressing complexity with a simple framework for action (Tomas J. Aragon, 2014)

The PHD CID Model

The PHD CID model is anintegrated model forpreventing and controllinginfectious diseases. Alsoconsider the following: (1)Is there asymptomaticinfectiousness? (latentperiod is shorter thanincubation period), (2)What is the generationtime?, (3) What are theethical considerations?,and (4) Do you have thepolitical and logisticalsupport to be successful?

A) Microbial Agent inB) Reservoir or

C) Source

E) Mode ofTransmission

G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry

Reservoir / Source1 Air2 Water3 Food4 People5 Animals & vectors6 Vehicles (e.g., injection)7 Soil & debris

Modes of transmission1 Contact - direct2 Contact - indirect3 Droplets4 Airborne5 Vehicle-borne6 Vector-borne7 Vertical (mom-child)

The 7 Habits of Uninfected People1 Safe consumption2 Personal hygiene3 Covering your cough4 Getting vaccinated5 Using “protection”6 Reducing special risks7 Basic infection control

Transmission Containment Strategies1 Reduce contact rate2 Reduce fraction of population that is infectious3 Reduce biological infectiousness

4 Reduce biological susceptibility5 Interrupt transmission (physical, chemical)6 Reduce fraction of population that is susceptible



Complexity and why it matters

What is a complex system?

1 A population of diverse agents, all of which are

2 connected, with behaviors and actions that are

3 interdependent, and that exhibit

4 adaptation and learning.

Why do we care?

Often unpredictable

Can produce large events

Can withstand substantial trauma

Can evolve along divergent pathways

Can produce “tipping points” (e.g., epidemics)

Can produce emergent phenomena (e.g., self-organization)



Spread of novel influenza A (H1N1) via global air travel

Destination cities and corresponding volumes of international passengers arriving from

Mexico between March 1 and April 30, 2008. A total of 2.35 million passengers flew

from Mexico to 1018 cities in 164 countries. Source: Khan et al. (2009), PMID

19564630Tomas J. Aragon, MD, DrPH (SFDPH) Preparing for Microbial Threats to Health June 9, 2014 10 / 33


Mitigating complexity

Be humble

Expect to fail

Expect the unexpected

Expect unintended consequences

Expect big events and tipping points (e.g., epidemics)

Beware of pathway dependence (irreversible evolutionary divergence)

Harnessing complexity

Balance exploration (learning) and exploitation (execution)

Develop/use “simple” frameworks for action (this talk!)

Design for agility, adaptability, and responsiveness

Develop/use “simple rules” that spread

Every failure is a learning opportunity


Controlling microbial threats

Concepts for controlling infectious diseases

Transmission mechanisms

1 Chain model of infectious diseases

2 Natural history of infection and infectiousness

3 Convergence model of microbial threats

Transmission dynamics

1 Reproductive number

2 Infection rate among susceptibles

3 Generation time

Transmission containment

1 Control points, strategies, and measures


Controlling microbial threats Transmission mechanisms

Chain model of infectious diseases

Chain model

A) Microbial agent

B) Reservoir / Source

C) Portal of exit

D) Mode of transmission

E) Portal of entry

F) Susceptible host


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry




Chain model—Reservoir / Source

Reservoir / Source

Humans

Animals

Environment

A reservoir can alwaysbe a source, but notall sources arereservoirs.

For disaster planningor response, consider7 sources (see Figure).


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry




Chain model—Modes of Transmission

Modes of transmission

1 Contact—direct

2 Contact—indirect

3 Droplet

4 Airborne

5 Vehicle-borne (food)

6 Vector-borne (bugs)

7 Vertical (mom-child)


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry





Chain model—The 7 Habits of Uninfected People

The 7 Habits ofUninfected People

1 Safe consumption

2 Personal hygiene

3 Covering your cough

4 Getting vaccinated

5 Using “protection”

6 Reducing special risks

7 Basic infection control


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry






Good infection control starts with common sense:Cover the source!

Source: American Society of MicrobiologyTomas J. Aragon, MD, DrPH (SFDPH) Preparing for Microbial Threats to Health June 9, 2014 17 / 33


Disease scare at San Jose airport: 5 on flight from Asiaexamined—none found with SARS I

San Francisco Chronicle, Wednesday, April 2, 2003

In a false alarm heard ’round the world, the Santa Clara County healthsystem jumped into high alert Tuesday morning when an American Airlinesflight from Tokyo radioed that it might have five cases of the mysteriousflulike illness known as SARS on board.

[Joan] Krizman said she had no hard feelings about being treated as apotential health threat. The couple had just completed an exhausting,monthlong journey that included stops in Vietnam, Thailand and HongKong—three Southeast Asian hot spots for SARS.

“There were four fire trucks and eight police cars and four or fiveambulances,” she recalled. “I couldn’t believe it. I thought, ‘Wow! What’sgoing on here?’ Little did I know that we were to be the ‘victims.’ ”



Disease scare at San Jose airport: 5 on flight from Asiaexamined—none found with SARS II

The couple were asked twice to go to Valley Medical Center, and twicethey politely declined. “And then,” Krizman said, “they soon opened upthe ambulance doors and said, sorry, we’re taking you to the hospital.”

At the hospital, according to Krizman, “we were the only ones there notwearing masks.” When word got out just who they were, she said, “Peoplestarted running like crazy, like we were the bubonic plague. They put us ina room full of people with plastic boots and face shields and masks.”



Nurse wearing N-95 respirator outside of intensive care unit

Associated Press: In a ward at Sunnybrook and Womens Hospital inToronto, a nurse waits outside the door of a patient diagnosed with theillness [SARS].



Public-devised infection control, SARS outbreak, 2003



Infection control practices, SARS outbreak, 2003

Reuters: An Indian woman diagnosed with SARS sits on her bed at theDoctor Naidu Infectious Diseases Hospital in the western city of Pune.Doctors reported India’s first case of the disease in a marine engineer fromthe western coastal state of Goa on Friday, April 18, 2003.



WHO: Infection control gaps helped fuel UAE MERS surge

CIDRAP News, June 6, 2014

“Infection control breaches led to alist of factors that contributed to theApril surge of MERS-CoV cases inthe United Arab Emirates (UAE),the World Health Organization(WHO) said today after a team ofWHO and partner experts spent 5days assessing the situation there.”

Source: http://www.cidrap.umn.eduWHO finds hospital breaches worsened MERSoutbreak in UAE. Source: ArabianBusiness.com,June 7, 2014


http://www.cidrap.umn.edu


Natural history of infection and infectiousness (A vs. B)

Susceptible Latent period Infectious period

Incubation period Symptomatic period

Time ofinfection

Non-infectious

Non-diseased

No symptoms,Infectious

Susceptible Latent period Infectious period

Incubation period Symptomatic period

Time ofinfection

Non-infectious

Symptomatic,Not infectious

Non-diseased

A

B

When the latent period is shorter than the incubation period (B), an infected person becomes

infectious before symptom onset.



Convergence model for human-microbe interaction

Institute of Medicine. Microbial threats to health: Emergence, Detection, and Response.

National Academy Press, 2003


Controlling microbial threats Transmission dynamics

Epidemic curve in action, SARS outbreak, 2003

Number of probable cases of severe acute respiratory syndrome, by date of fever onset

and reported source of infection, Singapore, Feb 25-Apr 30, 2003. Source: CDC MMWR

(2003) PMID: 12807088



Reproductive number in action, SARS outbreak, 2003

Probable cases of severe acute respiratory syndrome, by reported source of infection,

Singapore, Feb 25-Apr 30, 2003. Source: CDC MMWR (2003) PMID: 12807088



In Contagion, Dr. Erin Mears (Kate Winslet) explains R0

Contagion is a 2011 public health thrillerdirected by Steven Soderbergh.

The reproductive number (R) is the number ofinfectious cases produced by an infectious caseduring its infectious period. R0 is the initial Rwhen an index case is introduced into acompletely susceptible population with nocontrol measures. Source (figure): PMID:19620267



Dynamics: Reproductive number and infection rate

Basic reproductive number

R0 = d× c× p

Transmission probability (p)

Biologic infectiousnessBiologic susceptibilityInterruptors (e.g., PPE)

Effective reproductive number

R(t) = R0 × x(t)

Infection rate among susceptibles

I(t) = c× p× P (t)

Source (figure): PMID: 19620267

d = duration of infectiousnessc = contact ratep = transmission probabilityx = fraction of population that is susceptibleP = fraction of population that is infectious



Reproductive number vs. Infection rate in susceptiblesControl strategies are derived from control points

Parameter control points

d = duration of infectiousness

c = contact rate

p = transmission probability

x = fraction of populationthat is susceptible

P = fraction of populationthat is infectious

Design control strategies

All communicable diseasecontrol strategies are designedto affect the five controlpoints.


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry

Transmissionprobability (p)

Contactrate (c)Fraction of population

that is infectious (P)Fraction of populationthat is susceptible (x)

Duration ofinfectiousness (d)


Controlling microbial threats Transmission containment

Transmission containment

Control strategies

1 Reduce contact rate (c)

2 Reduce fraction of population that is infectious (P )

3 Reduce biological infectiousness (affects p)

4 Reduce biological susceptibility (affects p)

5 Interrupt transmission (physical, chemical) (affects p)

6 Reduce fraction of population that is susceptible (x)

Control measures . . .

are interventions designed to address control strategies. Always considermutliple perspectives: host, agent, infectious sources, and environment(physical, social, economic, political, etc.)


Integrated model for controlling microbial threats

SFDPH PHD Controlling Infectious Diseases (CID) ModelTransmission mechanisms, dynamics, and containment (Tomas J. Aragon, 2014)

The PHD CID Model

The PHD CID model is anintegrated model forpreventing and controllinginfectious diseases. Alsoconsider the following: (1)Is there asymptomaticinfectiousness? (latentperiod is shorter thanincubation period), (2)What is the generationtime?, (3) What are theethical considerations?,and (4) Do you have thepolitical and logisticalsupport to be successful?


C) Source


G) SusceptibleHost

D) Portalof Exit

F) Portalof Entry




Transmission Containment Strategies1 Reduce contact rate2 Reduce fraction of population that is infectious3 Reduce biological infectiousness

4 Reduce biological susceptibility5 Interrupt transmission (physical, chemical)6 Reduce fraction of population that is susceptible


Integrated model for controlling microbial threats

Thank you! Any questions?


preparing for microbial threats to health: what every professional should know

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