Oxford languages definition of a virus: “an infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.”
As we sit in our houses hiding from a virus, I thought it might be time to learn about viruses. With a degree in basic chemistry the subject of viruses was only on the periphery of my learning. However, the longer the pandemic lasts, the more interested I become in virology and public health. The future of our country seems to depend on it.
Planet of Viruses was written in 2011 by Carl Zimmer and I think there is an update- but on my shelf I have the 2011 edition. This book was written with the University of Nebraska at Lincoln which is the place my parents met in the late 1960s. The entire Kinyoun clan has a large representation of veterinarians, medical doctors and other scientists from this institution- I am revealing my bias right here.
Here is a list of viruses with a short blurb explanation:
Rhinovirus: the common cold. Ten genes each (of the twenty thousand genes in our bodies). This virus lines the cells in our nose, throat, and lungs. In each host cell it makes copies of its genetic material before ripping its host apart and releasing copies of the virus. Because of the mild nature of this virus it may be advantageous to keep it alive in our population for “training” purposes. With it, our immune systems are properly trained in how to manage a virus, albeit a mild one, before coming in contact with something much more virulent.
Influenza Virus: Well duh....what is that? Sorry for the sarcasm. Also just ten genes (like cold virus). Spread from cell to cell in an airway it is like a lawn mower destroying cells and mucus in its way. Originated in birds. Seems to jump between humans, horses, dogs and pigs doing a process called “reassortment” along the way. This means the virus is any given combination of genes from any of these animals at any given time- always fluid and always changing it is impossible to entirely predict which strain will dominate any given year.
Human Papillomavirus: Begins when virus injects its DNA into a host cell, often epithelial cells- skin and mucous membranes. Cell makes HPV proteins from the DNA. The proteins start programming the cell. It duplicates itself. If on epithelial cells, these eventually rise to the top of our skin layer and die off- leaving a fresh layer underneath. Many people live peacefully with HPV for this reason- they are constantly shedding enough virus to keep their system in check. If, for whatever reason, the excess virus is not shed in normal cycle of epithelial growth and regrowth, a tumor forms- and manifests itself as cervical cancer.
Bacteriophages: A possible alternative to antibiotics in fighting bacteria, this is a potential future treatment option in modern medicine. First studied in World War I in soldiers with dysentery, it has only recently been seriously considered as a viable treatment. Viruses may be the solution to antibiotic resistant bacterial infections.
Marine Phages: Outnumber anything else in ocean by 15 to 1. Ninety percent of their genetic makeup is completely unknown to science. The viruses of the ocean exhibit stunning genetic diversity possibly because of the variety of hosts available for infection.
Endogenous Retroviruses: The existence of latent viruses was discovered in chicken DNA. Avian leukosis virus protein was found in healthy chickens. At some point in history, chickens had been infected by the virus and some had survived. These survivors had incorporated the genes for the virus into their genome- the advent of the endogenous or “generated within” virus. At any point, this endogenous virus could reactivate itself and start making chickens sick again. One such virus is responsible for proper attachment of the placenta in the uterus of a human mother.
Human Immunodeficiency Virus: First revealed itself as Acquired Immunodeficiency Syndrome (AIDS). Healthy men with severe pneumonia were mysteriously dying from it- their immune systems were failing. Eventually this was traced to the Human Immunodeficiency Virus (HIV)- a virus that attacks the immune system itself. It has two major forms- HIV-1 and HIV-2. Through genetic sequencing, these two forms have been traced to African primates- specifically sooty mangabeys, which are often kept as pets, and chimpanzees, often killed for meat. Unfortunately, a vaccine for HIV has not been found although a cocktail of drugs can dramatically influence the quality and longevity of life for people who are HIV positive.
West Nile Virus: This virus became a reality for our family when my aunt in Dallas Texas went to the hospital with what she thought was Covid-19 and found out she really had West Nile Virus. Really? You can get infected with West Nile Virus in a Dallas suburban backyard. Not pleasant, to say the least.
This virus emerged in the United States in 1999 although it probably originated in Africa. It seems to exist in many species of birds and is transmitted to other species via mosquito. When mosquitos “bite” humans they inject their saliva into their bloodstream, and with it is the West Nile virus. The dominant strain in the US is most close to that found in birds in Israel in 1998. Somehow these birds found their way to the US- and to the 62 species of mosquitos that have carried them across the US in just four years. In the worst 15% of cases, people develop encephalitis but most people just have fevers, rashes, headaches.
Severe Acute Respiratory Syndrome and Ebola: In 2002 an American businessman developed a fever on a flight back from China and died. It was the first of the SARS epidemic- evolved from the family of corona viruses-originally in Chinese bats. This outbreak of SARS was quickly contained with nine hundred deaths because they were able to track and contain the sources- a catlike animal called a civet was banned from open air markets and people infected were identified and quarantined.
In order to better identify viruses that might make a jump from animal to human there is a team of scientists from a project called the Global Viral Forecasting Initiative. They collect samples in an attempt to better understand exotic viruses and how they might influence global health.
Smallpox: This age-old virus taught modern medicine about vaccines. It infects the airway and causes flu-like symptoms followed by sores filled with pus. It traces back to Egyptian mummies three thousand five hundred years ago. It has wiped out countless civilizations of people. The “prevaccine” method of eradication involved rubbing a scab from a smallpox victim into a scratch of a healthy person. This often prevented the person from getting smallpox- but it wasn’t very reliable. It was rumored that milkmaids never got smallpox and a physician wondered if this was no accident- and it wasn’t. The cowpox illness was passed to most milkmaids and because of the immunity this provided they were protected against smallpox. The process was named “vaccination” after the Latin name of cowpox, Variolae vaccinae.
This is a major argument for better science education- a mere rumor about milkmaids led to a major advancement in western medicine. Think how many advancements would be made if knowledge were more than just a rumor?
Mimivirus: In 1992 a virus in the water of an English town caught the attention of officials looking for the cause of a pneumonia outbreak. They almost missed it because it was one hundred times larger than it was supposed to be. Besides being exponentially larger than expected, it contained proteins that look like proteins in our own human cells. This virus was able to do far more than viruses were thought capable of independently. This raises the question of what is a virus? And more importantly: what does it mean to be alive. According to the definition at the beginning of this post, a virus cannot reproduce independent of its host. For mimivirus, this is not true......Work for the future scientists to investigate this further.
Thanks to this book, and dead time created by the coronavirus of 2020(Covid-19- not the coronavirus of this post) I am much better informed and ready to explain viruses.
