May 1, 2020

By Dr. Diana Horvath and Dr. Curt Horvath 


The COVID-19 pandemic is a sobering reminder that the tiniest microbe can bring the human race to its knees.  

Viruses, bacteria, fungi, water molds and other microbes are everywhere in our world. The human body has 10 times as many microbial cells as human cells, and a 200-pound man likely carries around as much as 6 pounds of bacteria.  Most of our microbes are benign, and some are even beneficial like those in our gut.   

The same is true for plants: the majority of microbes are harmless or form symbiotic relationships that give and receive benefits from the plant host. 

Yet some microbes make people sick, and others attack the crops we rely on for food.  These bad actors are called pathogens. 

The two of us met in graduate school, studied molecular biology, and pursued parallel paths studying pathogens and host responses. Curt is a professor in the Department of Molecular Biosciences at Northwestern University, focusing on virology and antiviral immunity, and Diana heads the nonprofit 2Blades Foundation which advances genetic resistance to pathogens that attack our food crops.  

Another biologist couple, Jean and Peter Medwar famously wrote in 1977 that a virus is “a piece of bad news wrapped up in a protein.” Not all viruses are bad news, yet a few are very bad indeed — and SARS-CoV-2, the virus that causes the disease COVID-19, is among the worst. 

The simplest viruses are protein-coated nucleic acids — DNA or RNA — which are molecular blueprints for making copies of themselves.  Other viruses, like SARS-CoV-2  or the influenza virus, have additional molecules like lipids surrounding their protein-coated nucleic acids and protect them from the outside world (though soap can destroy this coating). 

Like other living creatures, viruses reproduce themselves, but since they don’t have the machinery and raw materials to make new viruses on their own, they must enter living cells and trick them into becoming virus factories. Within hours, a virus can copy itself hundreds or thousands of times, then leave the now-depleted host cell and move on to the next one, and so on. 

Some of the deadliest diseases of mankind are caused by viruses. Since the 1980s about 75 million people have been infected with HIV worldwide, killing nearly half from AIDS.  The Ebola virus has killed tens of thousands, and the 2018 flu season claimed 80,000 American lives, while a century earlier the 1918 influenza pandemic killed 50 million worldwide.  

As of today, the COVID-19 pandemic has infected over 3 million people, and in the US alone more than 1 million are infected and over 60,000 dead in just the past two months. 

To fight these kinds of bad actor microbial threats we need to understand them and find vulnerabilities and advantages for ourselves and our crops.  As molecular biologists, that’s what we live for. 

So let’s take a look under the hood.  

Coronaviruses were named for their appearance under a microscope — they have spikes that form crown-like projections, or corona in Latin.  The virus that causes COVID-19 is a member of the large Coronavirus family that can infect a wide range of animal species.  The virus is named SARS-CoV-2, due to its similarity to the virus that caused the SARS pandemic in 2003, which was called SARS-CoV. 

Both of these coronaviruses were introduced to humans from bats and other animals that likely came in contact in live game markets.  However, there are many differences which make COVID-19 a more destructive disease in humans.  For example, the virus has acquired the ability to spread more easily throughout the human population by taking a longer time to cause observable symptoms (cough, fever, etc.), and this enables it to begin replicating before we know we should isolate ourselves. 

Plant pathogens also cause human misery and death by destroying our food. One tragic example occurred when a microbe called Phytophthora infestans, (an oomycete or water mold) was inadvertently transported by ship to Ireland in the 1840s. For several years this microbe (whose name aptly means “plant destroyer”) caused the late blight disease of potato that decimated the crop upon which the Irish poor depended for sustenance, with over 1 million dying of starvation and forcing at least a million more to flee to the US, Canada and other nations. 

Today the potato is the third most important food crop in the world, and is still ravaged by late blight.  Our other main food crops — corn, wheat, soybeans, and rice — are also victim to pathogens which attack with the same vigor as COVID-19.   

In plants, fungi are the most prevalent cause of disease.  Rust fungi that attack wheat have been around since the Roman Empire and threaten our very daily bread, because wheat supplies 20 percent of the world’s calories and protein. Fungal diseases are especially dangerous because they produce trillions of spores that can be carried by winds for thousands of miles, even across oceans, seeking a chance to attach themselves to the next susceptible crop. 

These kinds of threats to our health and our food are not new, and we have made important strides in how we study and fight them. But recombination and mutation are nature’s mechanisms for survival, and new threats continue to evolve.  

Pathogens never sleep. Thus, we can never be complacent and must apply our best minds to relentlessly pursue more knowledge, more tools, new methods.  

Thankfully, today many thousands of scientists throughout the world are focusing on these existential threats to our way of life and to our children’s future. 

The current crisis shows that we have failed to prepare for what is coming next, and we must learn to mitigate these risks by quickly and adequately funding research which has been proven to protect our health and the crops we need to survive. The cost of such research is an infinitesimal fraction of the $8 trillion governments have spent in just the last two months to stimulate the global economy and protect families from COVID-19’s economic harm. 

Thus, biological research on microbial threats to human and plant life is an insurance policy for our survival and success on this planet. We can pay a little now, or assuredly we will pay a lot more later.