from animals to humans: the rise of new infectious diseases thomas abraham
TRANSCRIPT
From animals to humans: the rise of
new infectious diseases
Thomas Abraham
Today’s class
The rise of emerging infectious diseases- from SARS to H5N1
Current controversy surrounding H5N1
Malaysian flying fox- Pteropus vampyrus
Copyright Adam Fink
1998 Malaysia An unusual disease breaks out among
people working in pig farms High fever, muscle pain, convulsions
and possible death Pigs were first affected, and
transmitted the disease to humans 265 human cases, 105 deaths Eventually traced to a previously
unknown virus: Nipah
Malaysian flying foxes had been noticed eating fruit from trees near the farm
Their droppings and saliva could have contained the virus which could have infected the pigs
Ebola Reston in the Philippines,2008/09
Photo credit: R. Dolan
Rift Valley Fever, East Africa
The emergence of new diseases
At least 20 new infectious diseases have emerged since the 1970s including HIV/AIDS, SARS, Ebola, Nipah, Marburg
All of them caused by viruses which passed from animals to humans
Re-emergence of infectious diseases
Penicillin and other antibiotics proved miraculously effective against a range of common infections and diseases -scarlet fever, diphtheria, meningitis, tuberculosis
Development of anti-viral drugs In the 1950s and 1960’s, plans made to
eradicate malaria, polio, tuberculosis and smallpox globally
US Surgeon General in 1969 “ We can now close the book on infectious diseases.”
The Surgeon General was mistaken
Malaria kills one child every 30 seconds, and one million people a year
One third of the world’s population is infected with TB
Polio has not yet been eradicated Smallpox the only successful
eradication programme
The microbes fight back
Drug resistant forms of disease causing agents developed
Increasingly TB does not respond to the earlier, cheaper antibiotics. MDR and XDR TB
The case of malaria- both parasite and vector became resistant to control methods
HIV Nearly 30 years ago, HIV/AIDS was
first identified and has since spread across the world
HIV= Human immunodeficiency virus AIDS= Acquired Immune Deficiency
Syndrome ( the advanced stages of HIV infection)
December 2009
Total: 33.4 million (31.1 – 35.8 million)
Western & Central Europe
850 000[710 000 – 970 000]
Middle East & North Africa
310 000[250 000 – 380 000]Sub-Saharan Africa
22.4 million[20.8 – 24.1 million]
Eastern Europe & Central Asia
1.5 million [1.4 – 1.7 million]
South & South-East Asia
3.8 million[3.4 – 4.3 million]Oceania
59 000[51 000 – 68 000]
North America1.4 million
[1.2 – 1.6 million]
Latin America2.0 million
[1.8 – 2.2 million]
East Asia850 000
[700 000 – 1.0 million]Caribbean240 000
[220 000 – 260 000]
Adults and children estimated to be living with HIV, 2008
December 2009
Estimated number of adults and children newly infected with HIV, 2008
Western & Central Europe
30 000[23 000 – 35 000]
Middle East & North Africa35 000
[24 000 – 46 000]Sub-Saharan Africa
1.9 million[1.6 – 2.2 million]
Eastern Europe & Central Asia
110 000 [100 000 – 130 000]
South & South-East Asia
280 000[240 000 – 320 000]Oceania
3900[2900 – 5100]
North America55 000
[36 000 – 61 000]
Latin America170 000
[150 000 – 200 000]
East Asia75 000
[58 000 – 88 000]Caribbean
20 000[16 000 – 24 000]
Total: 2.7 million (2.4 – 3.0 million)
December 2009
Global estimates for adults and children, 2008
• People living with HIV 33.4 million [31.1 – 35.8 million]
• New HIV infections in 2008 2.7 million [ 2.4 – 3.0 million]
• Deaths due to AIDS in 2008 2.0 million [1.7 – 2.4 million]
December 2009
Estimated adult and child deaths due to AIDS, 2008
Western & Central Europe
13 000[10 000 – 15 000]
Middle East & North Africa20 000
[15 000 – 25 000]Sub-Saharan Africa
1.4 million[1.1 – 1.7 million]
Eastern Europe & Central Asia
87 000 [72 000 – 110 000]
South & South-East Asia
270 000[220 000 – 310 000]Oceania
2000[1100 – 3100]
North America25 000
[20 000 – 31 000]
Latin America77 000
[66 000 – 89 000]
East Asia59 000
[46 000 – 71 000]Caribbean
12 000[9300 – 14 000]
Total: 2.0 million (1.7 – 2.4 million)
December 2009
Western & Central Europe
<100[<100 – <200]
Middle East & North Africa4600
[2300 – 7500]Sub-Saharan Africa
390 000[210 000 – 570 000]
Eastern Europe & Central Asia
3700 [1700 – 6000]
South & South-East Asia18 000
[11 000 – 25 000]Oceania<500
[<500 – <1000]
North America<100
[<100 – <200]
Latin America6900
[4200 – 9700]
East Asia3200
[2100 – 4500]Caribbean
2300[1400 – 3400]
Estimated number of children (<15 years) newly infected with HIV, 2008
Total: 430 000 (240 000 – 610 000)
December 2009
Western & Central Europe
<100[<100 – <200]
Middle East & North Africa3300
[1600 – 5300]Sub-Saharan Africa
230 000[120 000 – 350 000]
Eastern Europe & Central Asia
1400 [<500 – 2700]
South & South-East Asia11 000
[4900 – 17 000]Oceania<100
[<100 – <500]
North America<100
[<100 – <200]
Latin America3900
[2100 – 5700]
East Asia1500
[<1000 – 2300]Caribbean
1300[<1000 – 2100]
Estimated deaths of children (<15 years) due to AIDS, 2008
Total: 280 000 (150 000 – 410 000)
December 2009
Over 7400 new HIV infections a day in 2008
• More than 97% are in low- and middle-income countries
• About 1200 are in children under 15 years of age
• About 6200 are in adults aged 15 years and older, of whom:— almost 48% are among women— about 40% are among young people (15–24)
December 2009
• Children living with HIV 2.1 million [1.2 – 2.9 million]
• New HIV infections in 2008 430 000 [240 000 – 610 000]
• Deaths due to AIDS in 2008 280 000 [150 000 – 410 000]
2008 global HIV and AIDS estimates Children (<15 years)
How did this all happen?
HIV virus related to a group of viruses simian immunodeficiency viruses (SIV)
Closest relative an SIV virus found among chimpanzees in Gabon and Zaire
Could have been present in humans as early as the 1930s
Had probably begun to spread outside Africa in isolated cases by the 1960s
Social and cultural conditions required for an epidemic
HIV infection spread through bodily fluids: blood and sexual fluids primarily
Changes in social and sexual practices Great increase in numbers of injection
drug users Professional donors donating blood to
blood banks
Spread in AfricaIn Africa: Armed conflicts in the 1970s and 80s
disrupted societies Movement of soldiers and combatants Men going to work in urban areas
away from their families Women looking for ways to support
their families become commercial sex workers
Mother to child transmission
Issues in HIV/AIDS
Meeting the challenge of HIV/AIDs has two aspects: Prevention, and Treatment
Prevention
An average of over 7,000 new people get infected every day
New infections are outpacing people getting treatment by a 5:2 ratio; the AIDS pandemic cannot be stopped without effective prevention
More than 80% of transmission is sexual
Behavioral changes in sexual behaviour
Empowering women Decriminalising homosexuality and
encouraging access to treatment and prevention services
Encouraging drug users to use needle exchanges etc
Encouraging condom use/Male circumcision
HIV/AIDS as a human rights issue
Prevention through medical interventions
Research on vaccines showing some promise
Microbicides to use after exposure
Treatment
Getting people access to anti-retroviral therapy
33 million people living with HIV/AIDS. Only 14.6 million have access to treatment
Funding: costs US$ 143/person/year Ensuring the treatment is adhered to More infor: UNAIDS
(http://www.unaids.org)
Environmental change and disease
How did the Nipah get to Malaysia In 1997, giant forest fires broke out in
Kalimantan and Borneo in Indonesia
1997 forest fires in Kalimantan and Borneo
Haze reaches Malaysia, Singapore and Thailand
The speed at which disease travelled
In 1827, a cholera outbreak in north India
1830, carried by traders to Moscow 1831, reaches other European cities 1832 reaches North America
The speed at which it travels now
The SARS outbreak showed us, that a disease that is in Hong Kong today, can be in South east Asia in 3-4 hours, Europe in 12 hours, and North America in 18 hours
Summing up
Population growth has led humans to expand to new environments and come in contact with new pathogens
Social and cultural factors have contributed to the spread of new diseases
Science, censorship and H5N1
H5N1: aka “bird flu” First known cases of human infection
in Hong Kong in 1997 By end 2003, had begun to spread to
domestic and wild birds throughout Asia.
2003-2004 bird virus travelled to middle East, Africa, Europe.
Increasing numbers of human cases
Still an avian virus The number of cases still relatively
small, since the virus is not easily transmissible from avians to humans
If it were transmissible easily, could cause a pandemic with millions of deaths
Can H5N1 ever become transmissible between humans?
If so, what genetic changes would it be required to undergo?
Two teams began to investigate - one led by Ron Fouchier at Erasmus University in the Netherlands, and the other by Yoshihiro Kawaoka.
They genetically altered the virus, and used ferrets, to test whether it would transmit easily
Eventually, both teams came up with altered viruses that would transmit easily
“Because H5N1 mutations that confer transmissibility in mammals may emerge
in nature, I believe that it would be
irresponsible not to study the underlying mechanisms” Yoshihiro Kawaoka, University of Wisconsin and Tokyo University
“Aimed to investigate whether and how HPAI H5N1 virus can acquire the ability to be transmitted via aerosols among mammals and whether it would retain its virulence”
Ron Fouchier, Erasmus University, Rotterdam
“ If such viruses were misused or escaped from the lab, they would evolve in ways that cannot be predicted.” Paul Keim, US National Science Advisory Board for Biosecurity
“Making every effort to ensure that this information does not easily fall into the hands of those who might use it for nefarious purposes or that a biosafety accident esulting in an unintended release does not occur should be our first and highest priority.”
Michael T Osterholm, University of Minnesota
The two research teams submitted their findings to Science and Nature respectively.
The journals asked the opinion of the US NSABB (National Science Advisory Board for Biosecurity)
NSAAB said this was dangerous, and the journals should publish only after removing essential details.
Essential details should only be given to those who needed to know.
This was controversial Censorship- should scientific findings
be censored? Who is to decide which researchers are
“qualified”? The viruses come from Indonesia,
Egypt and elsewhere. These countries are the most affected by H5N1. Should researchers from these countries be barred?
If so, why should they share virus samples?
WHO convened a meeting of international experts
General agreement that results should be published ( US experts disagreed)
Moratorium on this research until there was greater public understanding
Research on H5N1 must continue to protect public health
How do you get to know about stories like this
Nature Science WHO
Community of journalists and scientists
Laurie Garrett Helen Branswell Martin Enserink Vincent Racniello Seth Mnookin And many many more….