How Viruses Are Important for Human Health

 by Nikhil Sen

The COVID-19 pandemic affected the world deeply and as a result the narrative against viruses became embittered. People, businesses and entire economies are still recovering from the absolute shutdown of almost everything. Recorded instances of pandemics have increased over the centuries with the Spanish Flu infecting about one-third of the world’s population and a resultant death toll of 50 million in 1918-1919. Coronavirus infected 696 million worldwide, with associated deaths just under 7 million, showing the devastating effects of these two different viruses. The pandemic meant that viruses were portrayed in a wholly negative light, even though less than 0.0001% of viruses are pathogenic (capable of causing disease) and are essentially a small portion of genetic material in a protein capsule. In essence, viral particles are very important to humankind. 

Due to recent technological developments in microbiology and virology, scientists have found ways to manipulate viruses. Oncolytic viruses are used to infect and destroy cancer cells. The first was a modified herpes virus, and since then other viruses such as polio, rabies and adenovirus (which causes multiple different infections, such as pneumonia or conjunctivitis) have been used successfully as part of cancer therapy. This method of immunotherapy represents promising progress in the treatment of cancers. Cancer cells are effectively malfunctioning cells that cannot stop dividing, this means that they often have an impaired defence against viruses, making them more susceptible to infections. The oncolytic virus infects the cell, and replicates itself until the cancer cell bursts, initiating an immune response as cancer antigens are released, which eliminates remaining tumour cells in the body. Yet viruses’ aid in the fight against cancer goes unnoticed by most.

Viral particles can be modified to carry medicine to specific parts of the body which are virtually inaccessible to regular pharmaceutical products. Drug delivery via viral nanoparticles is considered an innovative step in the ability to treat many different diseases. Viral nanoparticles have properties which give them a wide range of applications, including vaccines, antimicrobial therapies, cardiovascular therapies, gene therapies, as well as imaging. Vaccines are probably the most well-known implementation of viral particles - inactive viral particles are injected into the body stimulating an immune response. The immune system has an immunological memory in both B and T lymphocytes (a type of white blood cell). When the real, active virus enters the body, it is recognised due to the previous exposure and destroyed quickly.

Viral particles in antimicrobial therapies (formulations that treat microbial infections, which are not just bacteria, but also fungal, viral and protozoan), have the potential to kill larger microbes such as bacteria and fungi, in the same way that they kill our own body cells. Bacteriophages are viruses that solely target and kill bacteria. They have proven effective in the fight against multi-antibiotic resistant bacteria. These types of phages are by far the most populous biological entity on the planet, with an estimated figure of over 10 to the power 31 bacteriophages, which is more than all organisms combined.

The thing that interests me most about viruses is the way they have secretly influenced the evolution of life. Viruses introduce genetic information and help shape genomes and the immunity of all cellular life. Over 65% of the human genome originates from viruses and a smaller percentage comes from bacteria and other microbes. Retroviruses integrate themselves into the host's genome - this has led to large numbers of retroviruses having amassed in some eukaryotic genomes. Some retroviruses activate cancer-causing genes (called oncogenes), which contribute to the genetic liability of increased cancer risk from family history. Genes derived from viruses may contribute to long-term memory formation, neurotransmission and brain development. The integrated retroviruses are also thought to form the foundational layer of cells from the placenta, regulate embryonic development and control birth timing.

In conclusion, viruses have moulded our existence in unexpected ways, and have the power to impact our lives positively if we can harness their potential.