Re-emergence

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En provenance du cours de The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

577 notes

The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

577 notes

Not so long ago, it was almost guaranteed that you would die of an infectious disease. In fact, had you been born just 150 years ago, your chances of dying of an infectious disease before you've reached the tender age of 5 would have been extremely high. Since then, science has come a long way in understanding infectious diseases - what they are, how they spread, and how they can be prevented. But diseases like HIV/AIDS, Malaria, Tuberculosis, or the flu are still major killers worldwide, and novel emerging diseases are a constant threat to public health. In addition, the bugs are evolving. Antibiotics, our most potent weapon against bacterial infections, are losing their power because the bacteria are becoming resistant. In this course, we'll explore the major themes of infectious diseases dynamics. After we’ve covered the basics, we'll be looking at the dynamics of the flu, and why we're worried about flu pandemics. We'll be looking at the dynamics of childhood diseases such as measles and whooping cough, which were once considered almost eradicated, but are now making a comeback. We'll explore Malaria, and use it as a case study of the evolution of drug resistance. We'll even be looking at social networks - how diseases can spread from you to your friends to your friends' friends, and so on. And of course we’ll be talking about vaccination too. We’ll also be talking about how mobile phones, social media and crowdsourcing are revolutionizing disease surveillance, giving rise to a new field of digital epidemiology. And yes, we will be talking about Zombies - not human zombies, but zombie ants whose brains are hijacked by an infectious fungus. We're looking forward to having you join us for an exciting course!

À partir de la leçon

Emergence

In module 7 of the course, we’ll look at so-called emerging infectious diseases. These are diseases that are causing new problems. They include infectious agents that are new to humanity, but also infectious agents that were once controlled and are now returning, particularly those that are evolving around formerly very effective public health tools like drugs and vaccines. This means much of the week involves a discussion of evolution. We will look at these emerging diseases and ask, where do they come from and what can be done about them? You will learn about new ideas for managing evolution, and some of the societal challenges involved. We will also look at the related question of how some diseases evolve to be nicer or nastier to their hosts.

Disease Emergence9:49

Re-emergence5:27

Evolution General5:38

Rencontrer les enseignants

Dr. Ottar N. Bjornstad
Professor of Entomology and Biology
Department of Biology
Dr. Rachel A. Smith
Associate Professor
Department of Communication Arts & Sciences and Human Development & Family Studies
Dr. Mary L. Poss
Professor of Biology
Department of Biology
Dr. David P. Hughes
Assistant Professor of Entomology and Biology
Department of Biology
Dr. Peter Hudson
Willaman Professor of Biology
Department of Biology
Dr. Matthew Ferrari
Assistant Professor of Biology
Department of Biology
Dr. Andrew Read
Alumni Professor in the Biological Sciences, and Professor of Entomology
Center for Infectious Disease Dynamics
Dr. Marcel Salathé
Assistant Professor of Biology
Department of Biology

Folklore has it that a 1960s US Surgeon General, proclaimed that it is time to

close the book on infectious diseases, and declare the war against pestilence won.

All evidence indicates that this is a medical urban legend, since

there is no written or first hand testimony to this statement.

The urban legend does however, reflect the

overall optimism in the public health community

at that time.

For example, Sir Frank MacFarlane Burnet,

the 1960 Nobel laureate in medicine, declare.

One can think of the middle of the twentieth century as

the end of one of the most important social revolutions in history.

The virtual emil, elimination of the infectious

diseases as a significant factor in social life.

Today, 50 years later, infectious diseases are still

the second leading cause of mortality in the world.

Accounting for more than 15% of all deaths world, worldwide.

At the continental scale, almost 2 3rds of all

deaths in Africa, are still caused by infectious disease.

Our battle against lethal bugs is very much still raging.

The virtual elimination still stifles us.

To understand the current state of world health, it is

instructional to understand the world optimism from half a century ago.

It stemmed from the tremendous improvements made

in the decades following World War II.

With respect to nearly all aspects of infectious diseases.

First the discovery and mass production of antibiotics, such,

such as penicillin, allowed treatment of many nasty bacterial infections.

For which there had previously been no cures.

Second, mass vaccination campaigns were repeatedly rolled out to greatly

reduce many of the most lethal and debilitating viral diseases.

Indeed, Smallpox was at the time already on the brink

of being stamped out by the global Smallpox eradication program.

Third, widespread application of the insecticide DDT.

A practice abolished since, in the 1970s

because of its environmental and hu, human toxicity.

Had led to the first ever global decrease in many vector born infections.

Ranging from malaria to typhus and dengue.

In rich countries, this had also all taken place against the backdrop

of decreasing incidents of waterborne infections;

due to continually improving urban sanitation.

There were generally great courses for optimism.

Today somewhat more somber outlook comes from two reasons.

First, we have come to realize that the human host is

continually being challenged, by not only established, but also new pathogens.

One of the world's worst current killer.

The HIV/AIDS virus, for example, only emerged out of the jungles

of Central Africa, sometimes in the middle of the 20th century.

Emergence of new diseases is just a continuous process.

Second, several diseases against which serious inroads were

being made, have for various reasons started to reemerge.

Antibiotic resistance, insecticide resistance,

vaccine-driven evolution and vaccine refusal.

First,

bacterial evolution and antibiotic resistance.

Tuberculosis, the great killer of the 16th through 19th century, could

easily be cured by their antibiotic Streptomycin discovered in the mid 1940s.

However, by 1980 resistance had appeared. Since the appearance of the subsequent

multi-drug resistant TB strain, the worldwide in, incidence of tuberculosis

has been steadily increasing.

In 1970, the hope of the public

health community was to completely eradicate the disease.

In 1993, TB was declared a global

health emergency by the World Health Organization.

Second, vector evolution of insecticide resistance.

Insecticidal control of vectors can be a

very powerful weapon against vector borne infections.

Unfortunately, insects like bacteria, can evolve resistance.

Sri Lanka virtually eliminated malaria from the entire country during the 1960s,

using DDT to kill mosquitos. By 1970, the mosquitos

had developed DDT resistance.

Third, vaccines, like drugs, can drive evolution.

And there is evidence that both viral pathogens like Hepatitis B, and bacterial

pathogens like Streptococcus pneumonia, have changed over

time to get around vaccine induced immunity.

A perhaps more surprising cause of reemergence

of vaccine preventable infections, is vaccine refusal.

Both the Measles-Mumps-Rubella and the Diptheria-Tetanus-Pertussis vaccines,

have been the subject of recent vaccine scares.

Alleged severe side effects of vaccines.

The allegations have been unfounded.

However the subsequent large number of parents who have decided against

vaccinating their children, have lead to outbreaks of both

measles and pertussis in populations that otherwise had robust

[UNKNOWN]

immunity.

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