By the late 19th century, humans knew of the existence of viruses, but they could not see them. With the invention of electron microscope in 1891 by German engineers Ernst Ruska and Max Knoll, scientists could see all types of viruses and study them in detail.

No living organism is free from viruses. They can infect human beings, animals, plants and even bacteria. What are viruses?

According to a well-known science writer from the United States named Aparna Vidyasagar, viruses are microscopic parasites, which lack the capacity to thrive and reproduce outside of a host’s body. 

The interesting question about viruses is whether they are alive.

“Virologists say viruses are not alive because they don’t grow or eat or move themselves. They can’t reproduce on their own,” Sanjeevini Pertiwi, who studied infectious diseases, told The Jakarta Post on Monday.

Some scientists, according to Sanjeevini, argue that viruses are a kind of living organism; they simply do not carry out metabolic processes. They can replicate themselves only in a living host cell. Viruses are parasites. That is why they have to invade our cells, so that they can use the complex machinery, nutrients and energy in our cells to their advantage.

“Viruses take control of the cell and give instructions to make millions of copies of themselves using their genetic blueprint,” Sanjeevini said. 

Whether viruses are alive or not, some of them are undoubtedly killers.  

According to the World Health Organization (WHO), viruses kill 15 million people every year all over the world. The smallpox virus killed 500 million people in the 20th century and the Spanish flu killed some 50 million people from 1918 to 1919. Now we have the novel coronavirus (SARS-CoV-2), which is destroying the lives of people all over the world.

As of June 15, according to worldometers.info, COVID-19, the disease caused by the SARS-CoV-2 virus, had infected 8,108,651 people and taken the lives of 438,596 people worldwide in less than seven months. 

Indonesia, the fourth most populous country in the world, is no exception. As of June 15, the country had reported 39,294 COVID-19 cases and 2,198 deaths in 105 days of record keeping.

How many types of viruses are there on Earth?

There are, perhaps, millions of types of viruses on our planet. According to Columbia University epidemiologist Stephen S. Morse, there could be about one million types of viruses in vertebrates, including humans. But this was an estimation from 27 years ago.

About 7 years ago, new details emerged regarding the number of viruses that infect mammals.

According to www.virology.ws, a group of scientists conducted a new study whose results were published on the website of the American Society for Microbiology. The researchers found that there were at least 320,000 types of viruses that could infect mammals.

What about human beings?

On March 4, livescience.com, a well-known online journal that specializes in health matters, published an interesting article titled “The 12 deadliest viruses on Earth”.

Of the 12, the most lethal virus is smallpox, which killed one in three people it infected. It killed 500 million people and 90 percent of the native people in the Americas. For thousands of years, people suffered from this disease. But in 1980, the World Health Assembly proudly declared that the world was free of the smallpox virus. The eradication of the virus through a vaccine was among the greatest achievements of humanity. 

A second lethal virus is HIV (human immunodeficiency virus), which was first identified in the early 1980s. HIV causes AIDS (acquired immunodefieciency syndrome), which has killed 32 million people worldwide. HIV has no vaccine yet, but powerful antiviral drugs can prolong the lives of those who have the disease.

Another deadly one is the Ebola virus, which was first detected in Sudan and the Democratic Republic of Congo in 1976. It has a fatality rate of 71 percent. So far, the virus has been largely confined to Africa. It has many strains whose fatality rates differ.

“Do not ever think that Ebola is only present in Africa. We have a less harmful strain of Ebola called Ebola Reston in the Philippines, mainly in monkeys. This Ebola Reston cannot make people sick. The real problem comes if it mutates,” Sanjeevini said. 

Influenza is another deadly virus. It has many strains and mutates frequently. One of its strains was the Spanish flu, which killed 50 million people between 1918 and 1919.

In the 1950s, the Dengue virus appeared in Southeast Asia. It can be deadly if it is not treated quickly. Every year about 100 million people will become sick from dengue. Now we have a vaccine.

We have SARS-CoV or severe acquired respiratory syndrome (SARS), which originated in China in 2002. It killed 770 people.

Now we are facing SARS-CoV’s sister: the novel coronavirus or SARS-COV-2, which is extremely contagious and more lethal than its elder sister.

We have also other viruses like the Marburg virus, Rabies, Hanta virus, Rota virus and MERS-CoV (Middle East Respiratory Syndrome or MERS). 

Play it safe: People eat at a restaurant in Jakarta on Monday. Due to the COVID-19 pandemic, restaurants have placed physical distancing signs on tables. Since viruses like the novel coronavirus are contagious, maintaining a safe distance is urged in public places. (JP/Arief Suhardiman)

How can we cure diseases caused by viruses?

“Vaccines are the best weapons against viral diseases. We should use antiviral drugs, not antibiotics, to cure these diseases. Unfortunately, we have neither a vaccine nor a cure for COVID-19,” Mery Harita, a doctor from West Jakarta, told the Post. 

There is a huge threat to human beings from various types of viruses in the future. Will they destroy human  race?

Humans are smartest species on the planet. They can develop vaccines for various types of viruses and medicines for the diseases they cause. Hopefully, our bodies will develop more antibodies to fight COVID-19 through our immune system.

The quick development of a vaccine or a proper cure for COVID-19 is very important. We all should follow health protocols to fight against COVID-19. Prevention is always better than cure.