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Our genomes are riddled with the detritus of ancient viruses. They infected our hominid ancestors tens of millions of years ago, inserting their genes into the DNA of their hosts. Today, we carry about 100,000 genetic remnants of this invasion. So-called endogenous retroviruses make up 8 percent of the human genome.

Lyme disease, Ebola and malaria all developed in animals before making the leap to infect humans. Predicting when such a 'zoonotic' disease will spark an outbreak remains difficult, but a new study suggests that artificial intelligence could give these efforts a boost. A computer model that incorporates machine learning can pinpoint, with 90% accuracy, rodent species that are known to harbour pathogens that can spread to humans, researchers report this week in the Proceedings of the National Academy of Sciences1. The model also identified more than 150 species that are likely to be disease reservoirs but have yet to be confirmed as such.

In order to be useful in treating human infections, antibiotics must selectively target bacteria for eradication and not the cells of its human host. Indeed, modern antibiotics act either on processes that are unique to bacteria--such as the synthesis of cell walls or folic acid--or on bacterium-specific targets within processes that are common to both bacterium and human cells, including protein or DNA replication. Following are some examples.

Iona Twaddell looks at the science of the waterborne disease cholera There are an estimated 3-5 million cases of cholera, a disease caused by the bacterium Vibrio cholera, each year. It is passed on through drinking water that has been contaminated with faeces from someone infected with the bacteria. Cholera causes vomiting and diarrhoea, leading to severe dehydration.

Cancer usually begins with one tumor in a specific area of the body. But if the tumor is not removed, cancer has the ability to spread to nearby organs as well as places far away from the origin, like the brain. How does cancer move to these new areas and why are some organs more likely to get infected than others? Ivan Seah Yu Jun explains the three common routes of metastasis.

A study in monkeys offers the first evidence that a leading drug developed to fight Ebola works against the strain causing the current outbreak in West Africa. Six animals were infected with a very high dose of the virus and then, three days later, half were given the drug, TKM-Ebola-Makona, which was designed specifically to fight the West African strain. The monkeys that received the drug survived, but all three untreated monkeys died, researchers reported on Wednesday in the journal Nature.

Components of the immune system called antibodies are found in the liquid portion of blood and help protect the body from harm. Antibodies can also be used outside the body in a laboratory-based assay to help diagnose disease caused by malfunctions of the immune system or by infections.

Neutrophils are our body's first line of defense against bacterial infections. After leaving nearby blood vessels, these cells recognize chemicals produced by bacteria in a cut or scratch and migrate "toward the smell". The above neutrophils were placed in a gradient of fMLP (n formyl methionine- leucine- phenylalanine), a peptide chain produced by some bacteria. The cells charge out like a "posse" after the bad guys.

Controversial new research suggests that contrary to the history books, the "Black Death" that devastated medieval Europe was not the bubonic plague, but rather an Ebola-like virus. History books have long taught the Black Death, which wiped out a quarter of Europe's population in the Middle Ages, was caused by bubonic plague, spread by infected fleas that lived on black rats. But new research in England suggests the killer was actually an Ebola-like virus transmitted directly from person to person.

15min How do vaccines prevent disease - even among people too young to get vaccinated? It's a concept called "herd immunity," and it relies on a critical mass of people getting their shots to break the chain of infection. Health researcher Romina Libster shows how herd immunity contained a deadly outbreak of H1N1 in her hometown. (In Spanish with subtitles.)

Since 2003, the H5N1 influenza virus, more commonly known as the bird flu, has been responsible for the deaths of millions of chickens and ducks and has infected more than 650 people, leading to a 60 percent mortality rate for the latter. Luckily, this virus has yet to achieve human-to-human transmission, but a small number of mutations could change that, resulting in a pandemic. Now a team of investigators from St. Jude Children's Research Hospital, Stanford University Medical Center, and MacroGenics have developed an antibody which has proven 100 percent protective against the virus in two species of animal models.

4:43 Cancer usually begins with one tumor in a specific area of the body. But if the tumor is not removed, cancer has the ability to spread to nearby organs as well as places far away from the origin, like the brain. How does cancer move to these new areas and why are some organs more likely to get infected than others? Ivan Seah Yu Jun explains the three common routes of metastasis.

15. That's all you need to know about the measles. OK, that's not true at all. There's no one weird trick that will give you a flat belly (besides lying face-down on something flat), and there's no one weird number that explains measles epidemiology. But the basic reproduction number, or R0, of a disease does shed some light on which diseases become epidemics and how we can keep them in check.

A nationwide outbreak of a respiratory virus last fall sent droves of children to emergency departments. The infections have now subsided, as researchers knew they would, but they have left behind a frightening mystery. Since August, 103 children in 34 states have had an unexplained, poliolike paralysis of an arm or leg. Each week, roughly three new cases of so-called acute flaccid myelitis are still reported to the Centers for Disease Control and Prevention.

The CDC released travel health notices Tuesday that named two more places in which the disease has spread via mosquito bites: The US Virgin Islands and the Dominican Republic.  The Zika virus is primarily transmitted by Aedes aegypti, the type of mosquito responsible for spreading dengue, yellow fever, and a whole host of other tropical infectious diseases. Originally identified in 1947 in Uganda, Zika was relatively unknown until 2007, when there was an outbreak of the virus in Micronesia. The mosquitoes pick up the virus from infected people, according to the CDC. 

The origin of viruses remains mysterious because of their diverse and patchy molecular and functional makeup. Although numerous hypotheses have attempted to explain viral origins, none is backed by substantive data. We take full advantage of the wealth of available protein structural and functional data to explore the evolution of the proteomic makeup of thousands of cells and viruses. Despite the extremely reduced nature of viral proteomes, we established an ancient origin of the "viral supergroup" and the existence of widespread episodes of horizontal transfer of genetic information. Viruses harboring different replicon types and infecting distantly related hosts shared many metabolic and informational protein structural domains of ancient origin that were also widespread in cellular proteomes. Phylogenomic analysis uncovered a universal tree of life and revealed that modern viruses reduced from multiple ancient cells that harbored segmented RNA genomes and coexisted with the ancestors of modern cells. The model for the origin and evolution of viruses and cells is backed by strong genomic and structural evidence and can be reconciled with existing models of viral evolution if one considers viruses to have originated from ancient cells and not from modern counterparts.

This case study presents the story of Phil, an undergraduate majoring in biology, whose Russian cousin Dimitri has contracted tuberculosis (TB) from inmates at the prison where he works.  Phil learns that his cousin's failure to complete his antibiotic regimen likely contributed to the evolution of antibiotic-resistant TB in his body.  Phil consults with his friend Stacy, and together they try to understand Dimitri's condition by applying what they are learning in their genetics lab experiment about the role of random mutation in bacterial evolution (including the development of antibiotic resistance) through Luria- Delbrück fluctuation analysis. The same analysis includes calculation of the mutation rate, which Phil realizes is sufficient to cause MRSA and other antibiotic-resistant infections. This case study was originally developed for concurrent use in freshman/sophomore-level genetics, elementary statistics, and precalculus. However, it is also very appropriate for courses in introductory biology, evolutionary biology, and biostatistics. The teaching notes discuss various ways to run the case depending on the mathematics and biology background of students.

But this tiny sample turned out to hold tremendous scientific value. It was from a person fortunate to survive the deadly Ebola virus outbreak of 2014. Walker and her colleagues wanted to know if they could identify some special antibodies in that person's blood. If this person had special Ebola-neutralizing antibodies, that might help explain why that person lived. The antibodies might also help provide a template for future development of a vaccine. Or, they could be the basis for genetically engineered copies that could be manufactured at large scale, stockpiled and used to rescue people newly infected in an outbreak.

HIV is a disease of the gut, a concept that's easy to lose sight of with all the attention paid to sexual transmission and blood measurements of the virus and the CD4+ T cells it infects and kills. But the bottom line is that about two thirds of all T cells reside in the lymphoid tissue of the gut, where the virus spreads after exposure, even before it shows up in blood.

What does the Ebola virus actually do in your body? Why is it so dangerous and why does it kill so many people? We take a look at the apocalyptic war that rages in the body after an infection by the Ebola virus and the soldiers fighting.