What we thought were answers have turned into questions when it comes to the topic of viruses. Any perceived borders between human DNA and viral DNA have become blurred, making it unclear if we “have a virus” or if viruses actually “have” us.
More than 3,500 viruses have been classified. Viruses are so tiny (about a thousand times smaller than bacteria) that they can only be seen with a special electron microscope. They vary in form from spherical or rod-shaped to structures resembling lunar landing modules.
Viruses are responsible for relatively harmless ailments such as the common cold, warts, and chicken pox, as well as more serious illnesses such as mono, measles, gastroenteritis, herpes, shingles, viral hepatitis, influenza, polio, West Nile, Hantavirus, SARS, Ebola, and HIV/AIDS. Viruses cause 10 percent of all cancers. The health of our animal friends is affected by viruses that result in diseases including feline leukemia, Parvo, rabies, and bird flu. Use good hygiene and preventive practices to avoid contracting disease from insects or other animals.
Scientists debate amongst themselves whether viruses are living or not. Most scientists agree that viruses exist in a gray area between life and inanimate matter. To be considered as “living,” the simplest functioning unit of an organism (a cell) needs the capability to reproduce, eat, and die. Bacteria, human and plant cells, for example, meet this criteria as they all contain a nucleus with DNA that enables them to reproduce, they eat, and they die. Not so with viruses. They are simply genetic material (DNA or RNA) wearing a protein coat and don’t even have a nucleus. They don’t eat and can lie dormant, hovering between life and death for long periods of time. Living organisms must come to the assistance of these cleverly dependent viruses.
Without so much as a “howdy,” viruses enter living cells and hijack their host’s cellular activity by inserting their own DNA into the host cell’s DNA, for the purpose of using host cells as their own private virus nursery. The host cell may die during “viral childbirth” or it may live to slowly produce more viruses for years. Viruses can lie dormant in their host’s cells for decades, patiently waiting for some triggering event that instructs them to start reproducing viral genetic material. Using a kind of “primitive intelligence” to cleverly alter the host cell’s genetic code, viruses can avoid being detected by their host’s immune system.
Viruses are simple-minded: all they want to do is reproduce. To accomplish this, they can gain entry into the human body through vectors including birds, pets, mosquitoes, rodents, bats, ticks, and can even hitch a ride inside bacteria. They can also enter the body through mucus membranes or a break or cut in our first line of defense against infection (the skin), through contact with contaminated surfaces such as drinking glasses, doorknobs, or when we inhale viral matter that is shed from another person’s sneeze. Viruses can invade a variety of body tissues including respiratory cells (influenza), nerve tissue (shingles), or circulating immune cells (HIV/AIDS). Body fluids including saliva, blood, semen, nasal secretions, vaginal secretions, and sputum can shed viruses.
The encroachment of humans into all previously remote areas of our planet through international travel increases the risks of exposure to and transmission of viruses. Ecological imbalances from overpopulation and chemical poisoning of our global environment decrease our immunity and encourage viral mutations. Viruses are highly adaptable and are continually reinventing themselves, making it difficult for epidemiologists (scientists who study all matters of public health) to track them and to accurately predict their impact on public health.
Through sequencing of genetic code made it possible by the Genome Project, it is indisputable that viral DNA has been part and parcel of human DNA throughout the history of mankind. Genetically speaking, Viruses R Us.
