By: Chelsea Dong
Infectious diseases have impacted human lives for decades as the world has grown concerned with studying how they devastate the host organisms they infect.
During the early twentieth century, scientists solidified the scientific method of systematic study for infectious agents and, soon after, germ theory was established. However, at the time, viruses remained a new, undiscovered agent. Eventually, viruses would be found within tissue extracts as they progressed through the fine filters of the human body and were therefore defined as submicroscopic infectious agents.
Early experimentation and observation had already paved the way for the discovery of oncogenes, intrinsic components of viruses shown to cause cancer. In 1908, Vilhelm Ellerman and Oluf Bang collaborated to illustrate the filtering of extracted devoid cells and bacteria spreading leukemia between chickens. Peyton Rous, two years later, had then come upon the realization of the chicken sarcomas being serially transferred from one animal to another through cell-free tumor extracts. The infectious agent, the Rous sarcoma virus (RSV), had been one of the first animal viruses discovered as it pioneered the discovery with a cancer-causing agent utilizing genetics.
From the rumors that the contagious generation of cancer via a contagious infectious agent which spread between two individuals through intimate interactions, many individuals initially assumed that cancer spread between spouses, mothers to children, and from patients to caregivers. The interest in infectious agents as a potentially common cause of cancer began with the formulation of germ theory in the early twentieth century. Despite various bacteria, yeasts, fungi, and protozoans being mysteriously rumored to be the potential agents that transfer cancer, studies failed to show a positive correlation between the submicroscopic infectious agents and cancer. In subsequent years, other infectious agents did not demonstrate a connection between the DNA tumor viruses and more common human cancers.
In reality, there are few known viruses that have similar dramatic effects on humans compared to the chicken's RSV cancer-causing DNA. The Human Papilloma Virus, acquired as a sexually transmitted infection, is known to cause cervical cancer, among a few other links between viral infections and oncogenesis. Beyond that, however, new developments in the study of submicroscopic organisms with the use of RSV have provided researchers with well-defined regions of DNA sequence known to have a direct relation with cancer development.
With that knowledge in mind, it poses the question: How are submicroscopic agents alive, what are their origins, and how do they spread?
Through the peculiar limitations and demands of what we may describe to be labeled as an organism, biologists agree that all living organisms exhibit some fundamental, shared properties: growing, reproducing, maintaining an internal homeostasis, responding to stimuli, and carrying out various metabolic processes. However, viruses can avoid fitting into the aforementioned criteria by exhibiting different characteristics. From inhaling particles expelled when another person coughs to eating without washing one's hands, people expose themselves to a meager number of virus particles as they gradually become infected and ill many days later as the viruses replicate within our bodies. This is accompanied by the realization of viruses evolving as each individual must receive a flu vaccine every year because the influenza virus changes as the years progress.
The question of where viruses come from proves itself to be a debate among virologists as many people voice three main hypotheses.
The progressive theory states that viruses originated from hereditary components that acquired the capacity of passing through cells. Following the Progressive Hypothesis, it suggests that viruses are founded by the progressive process of gathering genetic elements, having portions of genetic material be able to move within the genome, and also have them achieve the capability of living cells and to enter others.
The regressive, or reduction, hypothesis claims viruses that originate from normal cells that have atrophied to genes and coat protein, the genes of poxviruses and herpes viruses have double-stranded DNA and the viruses have 80 to 100 genes.
The virus-first hypothesis states that for the viruses to have initially predated or co-evolved with their general cellular hosts. This particular theory proposes the thought of viruses developing into more intricate free-living organisms, such as bacteria, or cells. With the curiosity of the source of viruses themselves, the theory of having similar ancient proteins grown to move from one being to another remains a possibility.
The question of the origins of viruses is accompanied by the awareness of taking preventative measures to keep oneself healthy. This includes covering one’s face when coughing or sneezing and washing one’s hands before eating to ensure safety from various bacteria. Moreover, advances in vaccinations and medicine have given more individuals higher chances of survival after viral infection. When taking even the smallest acts of precaution, the population is sure to appreciate you for taking into consideration the health of those around you. During the ongoing COVID-19 pandemic, each individual should become more aware of the environment filled with potential germs and take steps towards preventing others from being exposed, and we have germ theory and early study of submicroscopic organisms to thank for the knowledge of how to keep ourselves safer and healthier.
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