Dr. Tim's Spineless Wonders

What has a fly with a flu to do with you?

Wednesday, April 1st, 2020

Viruses are at the top of nearly everyone’s list of concerns right now, and understandably so. COVID-19 has wreaked havoc within our medical community and our current way of life. Ripple effects to our economy are yet to be determined – huge ramifications for such a tiny, sub-microscopic “bug.” Viruses are so small that 100 or more can exist in the shadow of a single bacterium. Only a very powerful and sensitive microscope can visually detect them.

As far as science can tell, viruses have always existed. There is no getting away from them. There are literally millions of them, and they are everywhere in the world. Though most are innocuous, there are always some that can invade and infect the living cells of other life forms. Once inside, they multiply by replicating themselves again and again using the host’s biological mechanisms.

Are viruses alive? Viruses exist as lifeless, inanimate molecules composed of pieces of nucleic acid contained inside a special protein and lipid coat, referred to as virions. Yet they sometimes, somehow, enter into and replicate themselves within the living cells of a new biological host, almost as if they were alive. As a result, most scientists today consider viruses as being in a gray area between living and nonliving.

After viruses multiply, they can be spread to people in many ways. Some are passed on through contaminated food or water or because of a lack of sanitation. Other viruses are spread directly from one infected person to another, such as via sexual contact or by exposure to infected blood. Still others, including the common cold, influenza and corona viruses such as Covid-19, are even more contagious and can be spread indirectly and from a distance by coughing, sneezing or touching contaminated surfaces.

Insects play a significant role in transmitting viral diseases to both animals and plants. In earlier Spineless Wonder columns, I have written about insects and other arthropods as vectors, or transmitters, of human diseases. For example, encephalitis, chikungunya, yellow fever, dengue, West Nile, and, most recently, Zika, are all viral diseases transmitted to humans by mosquitoes. Lice, fleas and ticks are also common vectors of infectious viral agents, including heartland virus, and Colorado tick fever.

When I think about diseases and the insects that carry them, I sometimes wonder if insects are susceptible to viruses, and if so, why are they are not affected by the diseases they carry? It turns out that all living organisms can become infected by viruses, including insects. However, viral diseases are quite host-specific, meaning that one specific virus may harm a certain group of animals but not others. Plant viruses don’t transfer to fish, pet diseases are not necessarily a threat to people, and vice versa. The point is that insects can suffer from viral infections, which, while devastating to the insect hosts, are harmless to humans.

Interestingly, however, we have learned that in some exceptional cases, the transmitted diseases actually do affect the insect itself. For example, a series of studies beginning a decade ago found that carrying malaria actually does increase the mortality risk to a mosquito. But recent follow-up studies are now showing that a mosquito’s immune system can respond, making it able to withstand malaria-causing parasites. It is hoped that this finding might possibly lead to a new understanding of our own immune system and ways humans might combat disease, which is why insect pathology (a specialized study in entomology) is so important.

The immune system is a remarkable piece of biological engineering. Viral infections in animals can be eliminated because the body’s immune system fairly quickly identifies the invading virus and produces antibodies of its own that seek out and destroy it. Animals of all kinds have this remarkable capacity. Even insects. The immune response of insects is actually quite similar to that of mammals. They can become sick just like people or pets can, but if their immune systems work quickly enough, they can ward off a disease and will survive.

We have learned to work with the natural immune system in amazing ways. Once the germ theory was established and specific microbes were implicated as the cause of certain infectious diseases, scientists found that human immune responses can be quick-started by injecting vaccines into a person. Once artificially activated, the immune system can produce antibodies against a specific virus – even before that virus invades. This discovery was a game changer for humanity and continues to protect millions of people each year from an array of potential threats including diphtheria, tetanus, whooping cough, polio, measles, mumps, rubella, hepatitis, influenza, cholera, plague, rabies, yellow fever, tuberculosis, typhoid fever, and chickenpox. Vaccines are currently being developed for AIDS, Ebola and Zika.

With such a proven track record we can be confident that vaccines for coronaviruses are on the horizon as well. Coronaviruses comprise a small group of viruses; only seven are known to infect humans. Four cause symptoms similar to the common cold, and three are known zoonotic (begin in animals and spread to people) diseases that are much more serious and can inhibit and compromise respiratory functions (think pneumonia). These include SARS, severe acute respiratory syndrome, first discovered in 2002; MERS, Middle East respiratory syndrome, first discovered in 2012; and now COVID-19, the cause of our current pandemic.

COVID-19 is an acronym that stands for coronavirus disease of 2019. In addition to respiratory impairment, what makes coronaviruses so deadly is the fact that they are easily mutatable, so can suddenly change their capacity to infect, what host they can infect, how quickly they can infect, and how they can become transmitted. COVID-19 has given us all of that, plus it is so new that we have no natural or acquired immunity, no vaccines or even proven medicines to combat the specific symptoms of which we are just learning.

Of course, we are not entirely without hope. We have been given societal tips and behavioral modifications proven to limit the infection and spread of the pandemic. And, not to minimize its potential threat but rather to give hope, we have the following poem that seems to be particularly fitting right now. It was written by Ogden Nash, America’s best-known producer of humorous poetry.

Text of old poem

Not only does this limerick elicit a slight smile because of its play on the use of English homonyms and its light humorous story line but it also causes some deeper reflection when pondered more closely. My interpretation is that the two insects (a fly and a flea) both come down with, and are suffering from, the flu, which can be considered poetic justice, for these two insects have transmitted disease-causing organisms and death to far more people in the world than all other animals combined. Not only that but they find themselves quarantined together in what feels like a prison – also a fitting recompense for their past nefarious behaviors.

A similar feeling of imprisonment is prevalent in our world right now as we socially isolate and quarantine ourselves in an effort to slow the pandemic. The uncertainty, fear and loneliness are burdensome, but what we can learn from Ogden’s verse is that there is hope. Eventually there will be relief because, like the flea and the fly, we too will find a crack or a flaw in the grip of this pandemic, and we will find a way to pull through. In time, strict social distancing will give way to new drugs, new medical techniques, and even new vaccines.

Life, as we know it, will restart.

We will recover.

We always do.

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Author: Dr. Tim Gibb, gibb@purdue.edu
Editor: Charles Wineland, cwinelan@purdue.edu
Category: Entomology
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