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None of them are really popular. Because they are responsible for a variety of annoying and sometimes serious diseases, they are stuck with a bad reputation. We often have no effective medicines to combat them. Today however, we celebrate them...
It’s Virus Appreciation Day
October 3 is a special day for recognizing viruses around the world. While we don’t want to miss out on the celebration, it begs the question: what are viruses actually? The answer requires a more in-depth look at their appearance and how they impact human life. By looking a little harder between the various epidemics and latest threats, we might even find some characteristics that put viruses in a positive light.
What makes a virus a virus?
Simply put: it’s genetic material. Viruses are not living beings, rather merely a type of infectious agent. They have no cells, cannot reproduce on their own and they do not have their own metabolism.
Viruses are very, very small. They are 20 -300 nm in diameter, a scale of one-billionth of a meter. Compared to all of the known microbes, viruses are teeny. They can only be visualized with fluorescent ultra-microscopy or electron microscopy.
Viruses can appear in two forms. First, they exist outside host cells as infectious particles called virons. In this form the virus spreads from one host to another. Most virons carry a protein envelope. They can exist for decades without a host and don’t lose their contagion potential. As soon as they are able to infect a new host cell, they change to their virus form and begin to replicate by borrowing the host cell’s DNA replication systems and metabolism.
There are currently around 3,000 known virus species. They can infect multicellular organisms like plants, fungi and animals, including human beings. Viruses also attack bacteria and other single-cell creatures. Every living being is host to a variety of virus species. Considering we have around 1.8 million plant, animal and unicellular species on earth, plus an enormous number of yet unknown species, we might expect an equally-enormous number of different viruses. The majority of them are still unknown.
Even though only a few viruses are known to us, their existence has been reported for a very long time. People were observed with polio and rabies symptoms as early as 2000 B.C. plus there are references in several documents and Egyptian hieroglyphs. Evidence of the oldest virus infection was found in the malformed bones of a 150-million-year old dinosaur fossil. Our understanding of viruses, their behavior and molecular mechanisms has been growing since the end of the 19th century, with more and more details coming to light.
Dangerous or beneficial?
Many viruses cause illnesses. Influenza often breaks out in the fall of each year for instance. And most childhood diseases are caused by viruses. While some diseases are common, such as Hepatitis or HIV, others have been nearly eradicated, such as smallpox. Serious epidemics such as the Ebola outbreak in West Africa or the Zika bug also pose periodic threats.
The fact is, because the virus and host cell metabolism are so closely intertwined, we lack the right medications to combat most viruses. By killing the virus, the host cell is attacked as well. On the other hand, there is a bright side related to medical development. Researchers recently discovered that modified viruses can be used to destroy targeted tumor cells or antibiotic-resistant bacteria for example.