Category Archives: Viral Disease

Zika Virus: What You Need to Know

Once relatively unknown, Zika virus is in the middle of an explosive epidemic in Brasil and other South American countries. While common symptoms are mild, pregnant women should be wary as contracting Zika virus during pregnancy appears to be linked to microcephaly in their babies.

What can we expect from Zika virus in the Americas? Read on to find out.

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The Concept of Viral Quasispecies

Many of us are familiar with the concept of a species at the macro (visible) scale. Dogs are dogs; pigs are pigs, and so on. Each is a distinct species based on the fact that they can only reproduce and generate fertile offspring with other members of the same species. Over the course of many generations mutations may arise in these populations which lead to different genotypes in the species. Left long enough, these two sub-populations may keep mutating to the point where they can no longer interbreed and become their own genetically distinct species. However, when you get down to the viral scale species becomes a much more difficult concept. Viruses don’t have sex in the traditional sense, so how do we determine what makes up a viral species?

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Viral fossils in our genome: Endogenous retroviruses

The last twenty years have been marked by a veritable explosion in sequencing technology. The Human Genome Project and it’s completion in 2003 was the crowning jewel of this burgeoning genomics revolution . The amount of information to come from this relatively new branch of science is literally mind-boggling and only grows with each passing day.

Interesting observations have come out of this massive amount of genomic data relating to the  non-coding DNA in our genome. Less than 2% of the over 3 billion nucleotides in our genome are responsible for coding all of the protein that makes up a human being. This leaves a large question as to what exactly that other 98% of our genome is up to. Large parts (roughly 50%) are known as “junk DNA” with no accepted role, although new research is beginning to shed light on the functions of this DNA. The remainder of our genome is composed of long and short repeated sequences, transposons, retrotransposons and the topic of today’s article: endogenous retroviruses.

These elements are not human, they are fully viral in origin. This means that our genome is not just ours alone, we carry the DNA of many viruses that infected our ancestors in every cell in our own bodies.

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Cancer-Causing Viruses: An overview

Can a virus cause cancer in humans?

In a word, yes. In fact, at this point multiple viruses have been identified as playing a role in the progression of many different cancers. The very first of these cancer-causing viruses was discovered by Peyton Rous in 1911, making the field of tumor virology over one century old. While this initial discovery was a virus that causes tumors in chickens, many important human cancers have since been discovered to have a viral component. The first human tumor virus to be discovered was Epstein-Barr virus (EBV) in association with Burkitt’s lymphoma in 1965 (see featured image). Since then many more viruses have been found to be tumorigenic (tumor-causing) in humans and more may still be awaiting to be discovered.

How is it that these many different viruses are involved in so many different types of cancers? What about these viruses makes them tumorigenic?

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The Problem with Polio

Child receiving polio vaccine.Polio is a disease that has seemed to fade away in the United States since the introduction of the polio vaccine in 1955. However, this disease is alive and well outside of the US despite a strong push by international agencies such as the WHO to eradicate polio in the last few decades. In fact, in 1988 the WHO pledged to eradicate polio by 2000, but this dream has yet to reach reality.

Why is the eradication of polio less successful than the effort to eradicate Smallpox, a goal achieved in the 1970’s?

These difficulties come from the nature of polio itself and the special challenges that this virus poses to those who would halt its transmission. Continue reading The Problem with Polio