A science teacher explains: What is a virus? Nearly 1031 types exist on earth

The very mention of the word virus sends a chill down the spine looking at the kind of harm coronavirus is doing to humans. But are all viruses harmful? Let us learn a little more about them.

The name virus was coined from the Latin word meaning slimy liquid or poison. Viruses swing on the boundary of what is considered life. They are generally much smaller than bacteria. On one hand, they have the key elements that make up all living organisms: DNA or RNA, the nucleic acids. On the other hand, they lack the capacity to grow and reproduce outside of a host body, which can be any living organism. They work by taking over the cellular machinery of the host cell and releasing new viral particles infecting more cells and cause illness.

ALSO READ | Milton and the Invisible Coronavirus: A book that tells kids how to fight the illness

They enter the host’s body through respiratory passages or open wounds. Certain viruses can also enter the host’s body through an insect’s saliva, after the insect bites. Yellow fever and dengue fever are examples of such viral infections. Humans also get infected by mammals like bats, pigs, camels and birds etc. Mammals and birds alone are thought to host about 1.7 million undiscovered types of viruses. Ebola and SARs (Severe Acute Respiratory Syndrome) carried to humans through bats, MERS (Middle East Respiratory Syndrome) through Camels, HIV through chimpanzees, etc, are some such examples.

Predominantly, viruses are known as the cause of infection. Widespread events of disease and death like the 2014 outbreak of Ebola in West Africa, the 2009 H1N1/swine flu global pandemic and now COVID 19 adds to this reputation. Most viruses indeed cause diseases ranging from a mild cold to serious conditions like severe acute respiratory syndrome (SARS), but all viruses are not harmful. Some viruses are helpful as they kill some harmful bacteria or fight against more dangerous viruses.

ALSO READ | In US, paediatricians recommend that children return to schools

Bacteriophages (or “phages”) are viruses that infect and destroy specific bacteria. These are found in the mucus membrane lining in the digestive, respiratory and reproductive tracts of humans. These are a part of our natural immune system.

Phages have been used to treat dysentery, sepsis, salmonella infections and skin infections for nearly a century. These viruses were isolated from sources, like local water bodies, sewage or even from infected patient’s body fluids, purified and then used for treatment. Phages have also been used successfully to treat drug-resistant infections.

Though an estimated 1031 types of viruses exist on Earth, yet, most of the time, we manage to live in this virus-filled world relatively free of illness. Pandemics like COVID 19 jolt us out of this state of complacency. To forecast the outbreaks timely and prevent them, scientists are researching the traits that may explain why some viruses, and not others, enter and infect humans.

ALSO READ | Why early child health immunisation is important in India

We are yet at a very nascent stage of our understanding of this viral component. The study or research of viruses has a huge potential in helping us understand viral infections, and importantly, how to fight the harmful ones.

(The writer is Lead, Curriculum – Science & Math at Shiv Nadar School)