Viral

Preface

The Covid-19 pandemic has thrust the virus center stage as a dangerous and dreaded foe similar to the way the influenza pandemic did a century ago. The causative viruses, SARS-CoV-2 and influenza A(H1N1), produce respiratory illnesses that are easily transmittable person to person and thereby quickly swept around the globe. Within months, both scourges sickened millions of people, and many died.

Although these two biologic entities currently dominate the spotlight, there are other viruses that deserve equal fear, concern, and attention, since some of the resultant diseases have a higher lethality as well as the capacity to cause more serious complications. Although these diseases are not transmitted by aerosol and are thereby less communicative, they, too, are spreading around the world at a slower — yet ever-quickening — pace thanks to climate change and human encroachment into previously isolated environments. In particular, a number of viruses have cleverly hijacked the mosquito to ensure their survival. These viruses are responsible for illnesses such as yellow fever, dengue, West Nile fever, and an array of diseases that cause dangerous inflammation of the brain called encephalitis. This includes eastern equine encephalitis virus, or EEE, which is known to have a death rate as high as thirty percent. As climate change advances, aggressive mosquitoes like the Aedes Asian tiger mosquito, which carry these dangerous viruses and which had heretofore been restricted to tropical climes, are progressively and relentlessly spreading northward into temperate regions, currently reaching as far north as the state of Maine in the USA and the Netherlands in Europe.

These other, fearful viruses couldn’t have picked a better vector. As obligate bloodsuckers to enable breeding, mosquitoes are high on everyone’s nuisance list. Most people can recall a disrupted summer slumber, or evening stroll, or hike in the woods, or barbecue on the beach, heralded by the characteristic whine of the female mosquito. As a creature superbly designed after almost one hundred million years of adaptive evolution (even dinosaurs were plagued by mosquitoes), the female mosquito invariably gets her blood meal or dies trying. For some reason that has yet to be explained, the female Asian tiger mosquito is particularly attracted to human females with blood type O, although other blood types or even human males will do in a pinch.

As a testament to the effectiveness of the mosquito — pathogen partnership, almost a million people die each year from a mosquito-spread illness. Some naturalists even posit that mosquito-transmitted illnesses have killed nearly half of all the humans who have ever lived.

— Robin Cook, MD