Viral infections kill nearly 50,000 people worldwide each day unless an epidemic is afoot. Usually, viral infections are non-fatal, but over the years a number of highly fatal viruses such as H1N1 or influenza, COVID19, Rabies, and Ebola have taken the lives of people around the world. Most common viral infections like common cold and different types of flu does not have dire effects on the person, but other infections like smallpox, measles, mumps, rubella, chickenpox, shingles, herpes, hepatitis, polio, HIV, SARS, dengue fever, Zika, and Epstein-Barr, might cause disfiguring or lead to death if not properly treated. However, not all viruses cause harm to us. Just like friendly bacteria, friendly viruses in our bodies help protect us from dangerous bacteria.
Viruses are microscopic organisms that exist everywhere on earth, within every ecosystem. The ultimate purpose of a virus is to reproduce. However, they are parasitic organisms that cannot survive or reproduce without a host. For this, a virus may infect humans, animals, plants and even other microorganisms like fungi or bacteria. One type of virus may infect one species but pose no threat to another. Viruses transmit from person to person, and from mother to child during pregnancy or delivery. They also spread through touch, saliva, coughing, sneezing sexual contact, contaminated food or water, and even by insects that carry them. Some can even survive on an object for a brief period.
When a virus infects a host, it inserts a copy of its genetic material into the host cell and takes over the functions of the host cell. Then the host cell begins reproducing with more viral protein and genetic material instead of the usual cellular products. After a period of time called the incubation period , the host is affected and starts to show symptoms. However, the symptoms may vary from fatal to none at all. When the host’s immune system recognizes the virus as an intruder, it responds by producing T-cells and antibodies that can bind to viruses and make them non-infectious by breaking down the genetic material in a process called RNA interference . Most fatal viruses are neurotropic, which means that they weaken the immune response by infecting the nerve cells directly, affecting the structure of the central nervous system (CNS) with delayed and progressive effects that can be severe.
Treatments for viral diseases do not use cures, rather vaccines to prevent their further spreading or antiviral drugs to treat them. Sometimes, the only solution that can be provided is to relieve the symptoms.
The development of antiviral drugs has been mostly in response to the AIDS pandemic. These do not destroy the virus but slow down the progress of the disease by inhibiting their growth. Antivirals are used to treat the herpes simplex virus, hepatitis B, hepatitis C, influenza, shingles, and chickenpox. A vaccine may consist of a weakened form of the virus, viral proteins called antigens that stimulate the body to form antibodies that will fight off future infections with the same virus or live-attenuated viruses such as immunization for poliomyelitis. Vaccinations exist for polio,
measles, mumps, and rubella, among others. The widespread use of these vaccines has reduced their prevalence dramatically. Vaccinations are generally the cheapest and most effective way to prevent viruses. Some vaccines have succeeded in eliminating diseases, such as smallpox. Vaccinations also carry the advantage of herd immunity , where a virus can be effectively eliminated from a community if a significant percentage of its inhabitants are properly vaccinated against it.