Emerging and re-emerging Disease

“Emerging and Re-emerging

humans disease

Abdul Aziz Djamal

Newly identifed and previously unknown

infectious agent that cause public health

Re-emerging Infectious

Disease



Infectious disease that have been known for

Examples

of Emerging and Re-Emerging

Infectious Disease: past 10 years

A Fauci,

2 HIV

Dengue

H Papilloma v

Ebola

Hanta virus West Nile virus

Tobacco

Malaria

Non-HIV tuberculosisRoad accidents

3 5 6 Influenza Polio SARS vCJD Measles

HBV + HCV

4

Log 10

RSV, Rota virus

7

Hospital infection Suicide

Major and minor killers: global impact viewed

on a ‘Richter’ (logarithmic) scale

Weiss & McMichael, 2004

1 Viruses

Infant/child ARI & diarrhoeal dis

Outline of Talk



Microbes, infectious diseases: recent trends



Infectious diseases as result of major changes in

human ecology and environmental – historical

transitions; current conditions



Examples of infectious disease risks



Travel, trade



Land use, agriculture



Intensive animal husbandry



Climate variability, climate change

Receding – then Resurging?

1950s-60s

: Infectious diseases apparently receding

in developed countries



Antibiotics and vaccines



Pesticides to control mosquitoes



Improved surveillance and control measures – internationally

coordinated

Early 1970s

: Authorities proclaimed end of

infectious disease era. Premature!

Choi Young-Soo/Associated Press - Yonhap

South Korean health workers disinfecting a chicken farm north of Seoul last week. Though 140 million birds have died or been killed as a preventive measure in Asia, the risks of wide human infection are not known.

South Korean health workers disinfecting a chicken farm in April, 2005. Though several hundred million birds have died or been killed as a

preventive measure in Asia, the human epidemic risk remains unknown.

Avian

’

flu, H5N1

Mad Cow Disease (BSE)



vCJD

Nipah viral encephalitis, Malaysia (1997-99)

Human-Microbe Transitions

over

the Millennia

Pre-historic: hunter-gatherers disperse into distant new

environments

1. Local agrarianism/herding: 5-10,000 yrs ago

2. Trans-continental: 1,000-3,000 yrs ago

3. Inter-continental: From c. 1500 AD

4. Today, global: Fourth historical transition

Suc

ces

sive

inc

rea

ses

in S

CA

•

Microbial adaptation and change

•

Human susceptibility to infection

ageing, HIV, IV drugs, transplantation, transfusion

•

Population growth and density

•

Urbanization, crowding – social and sexual relations

•

Globalization of travel and trade

•

Live animal markets

•

Intensified livestock production

•

Misuse of antibiotics (humans & domestic animals)

•

Changes to ecosystems (deforestation, biodiversity loss)

•

Global climate change

Clearing forests for agriculture

Viral haemorrhagic fevers in South America: peasant-farmers

Guanarito, Sabia, Kunjin, etc.

Eating infected animals

New variant Creutzfeldt Jacob disease (from BSE)

Cultivation of infected animals

Nipah viral encephalitis (pig farms in Malaysia)

West Nile virus (goose “fois gras” farms in Ramala, Israel)

Collection and trade of wild game

HIV (bush meat: primates) Ebola (bush meat?)

SARS (civet cat?)

1988/9 bans: Sale of nervous tissue and offal for human consumption Eating cattle >30 months old

Mammalian products in ruminant feed BUT: no ban on feed for swine or poultry

Incidence of BSE in UK, 1987-99

(c.180K cases)

01/97 Farm worker hospitalized with viral encephalitis (VE). 10/97 First death (pig-farm worker) from VE.

02/98 3 farm workers develop VE.

11/98 Health Minister declares it ‘Japanese Encephalitis’  mosquito control and vaccine program. But outbreak spreads.

1-2/99 Pig farmers begin ‘fire sales’ of pigs. Outbreak recedes a little. 02/99 Laboratories receive first samples of infected human

tissue. “New” virus? Mass pig culling begins. Villagers flee. 03/99 Virus isolated and identified with reagents used to characterize

Hendra virus (a recently-identified horse virus, from Queensland). 04/99 ‘Nipah virus’ discovery announced. Culling continues.

05/99 WHO declares outbreak over (265 cases, 40% fatal).

02/00 Last death. Fruit bats (flying foxes) deemed the likely reservoir.

Travel and Trade: examples

Aedes albopictus

mosquito eggs in

shipments of used tyres



dengue fever

Long-distance travel; wild animal trade



HIV/AIDS

SARS

Severe

Acute

Respiratory

Syndrome

A genetic model for the Coronavirus family.

Vietnam

Cambodia Lao PDR

China

Environmental Changes



Land use, forest clearance



Biodiversity losses, extinctions



Dams, irrigation

Village

(deforested)

Farm

(deforested)

Secondary

growth

Forest

Patz et al, 2003

0 .3 .6 .9 1.2 1.5

Log-transformed A. darlingi abun

1 2 3 4

No. of survey

sites = 2433

Forest fragmentation, hunting (wolves, passenger pigeons)

Less diversity of vertebrate predators and viral hosts

High Lyme Disease risk Expanding mouse populations Poor inter-species regulation

High tick density and high tick infection prevalence  infected deer

Many competent reservoir species  less dilution by

incompetent reservoir species

Lyme Disease: Influences of Habitat

Fragmentation & Biodiversity Loss

Adapted from: R. Ostfeld

Complex

life-cycle of tick

Climate Change and Infectious Disease

Some recent changes in ID patterns

may

reflect the

influence of climate change (debate continues)



Tick-borne encephalitis (north spread in Sweden)



Cholera in Bangladesh (strengthening relationship with El

Niño events)



Malaria ascent in east African highlands



Time-trends in incidence of (reported) food poisoning, esp.

NCEPH/CSIRO/BoM/UnivOtago, 2003

Dengue Fever:

Estimated geographic region suitable

for maintenance of

Ae. aegypti

, under alternative

climate scenarios for 2050

Risk region under medium emissions scenario, 2050

Darwin Katherine Cairns Mackay Rockhampton Townsville Port Headland Broome

.

.

..

.

.

..

Carnarvon

.

Darwin Katherine Cairns Mackay Rockhampton Townsville Port Headland Broome

.

.

.

.

..

.

.

Brisbane

.

Current risk region for

dengue _Darwin Katherine Cairns Mackay Rockhampton Townsville Port Headland Broome

.

.

.

.

.

.

.

.

Carnarvon

.

_{Risk region under high}

Source: Kris Ebi

Humans, domestic animals and wildlife are inextricably

linked by epidemiology of infectious diseases (IDs).

IDs will continue to emerge, re-emerge and spread.

Human-induced environmental changes, inter-species

contacts, altered social conditions, demography and

medical technology affect microbes’ opportunities.

Also:

New research, technology and collaborative networks

will also elucidate role of infection in diverse, mostly

chronic, diseases of unknown cause . . . .

INFECTIOUS CAUSES OF

CHRONIC DISEASE: Examples

Disease

Cervical cancer

Chronic hepatitis, liver cancer Lyme disease (arthritis)

Whipple’s disease Bladder cancer Stomach cancer

Peptic ulcer disease

Atherosclerosis (CHD) Diabetes mellitus, type 1 Multiple sclerosis

Inflammatory bowel disease

Cause

Human papilloma virus Hepatitis B and C viruses

Borrelia burgdorferi Tropheryma whippelii Schistosoma haematobium Helicobacter pylori Helicobacter pylori Chlamydiae pneumoniae

Enteroviruses (esp. Coxsackie)

Epstein-Barr v, herpes vv?

Mycobacterium avium sub-spp.

Conclusion I: Understanding what

promotes human-microbe contacts

(i)

Intensified modification/exploitation of natural

environments and food production.

(ii)

Disturbance of natural ecosystems and their

various internal biotic controls.

(iii)

Poverty, crowding, social disorder, mobility and

Conclusion II:

Microbes as Co-Habitants

Microbes’ interest is in survival and

reproduction. They have no malign

intent; morally neutral!

Their evolution-based drive to survive is

as strong as ours (and draws on

much

27 Dec 1997: Tropical Cyclone Sid