This is not a bacterium: some common misunderstandings about viruses

October 11, 2017

 

Reading time: 5 min | Difficulty: high | Sources: 3 of 8 are open access

 

Information is the gold of the modern age. Everyone is always seeking truth - googling any question that arises in a conversation. This constant search emphasizes the need to differentiate truth from myth. One of the themes that gets people’s attention, lately, is the occurrence of outbreaks like Ebola in Africa (2014-16) or the pandemic swine flu in 2009. Thus, let us clarify some common misunderstandings, because, in reality, bacteria and viruses are very different.

 

First, to understand both better, let us enter the microscopic world and talk about size. Viruses are smaller (10 to 100 times) than bacteria, which are 10 to 100 times smaller than the diameter of a string of hair. Bacteria are microscopic organisms capable of living and replicating independently and considered to be the first forms of life on Earth. Viruses are scientifically not considered alive as all of them lack any form of energy, metabolism, and ability to replicate or evolve without infecting a cell. So, what are they? They are an inanimate complex of proteins (typically arranged as a shield) with genetic information (DNA or RNA) inside. To multiply, viruses need to infect a cell, which can be a plant cell or a human cell - or even a bacterium.

 

No matter which type of  cell, a viral infection follows these general steps:

- attachment to and entry in the cell;

- production of the necessary proteins;

- replication of the DNA or RNA;

- assembly of the newly produced components;

- and release of new viruses into the immediate environment or into another cell.

 

Sometimes, the time between production and assembly of the components is very long, years even, so a person may carry a virus but not show any signs of illness. In this case, viruses enter a dormant phase. This happens for example with viruses causing AIDS (human immunodeficiency virus), chickenpox (varicella zoster virus) or cold sores (herpes simplex virus).

 

One of the most common myths about viruses is that viral infections, such as a cold or the flu, can be treated with antibiotics. However, antibiotics target only bacteria and are therefore ineffective at killing viruses. In fact, using antibiotics when you have a viral infection can disrupt your natural community of bacteria and contributes to the evolution of antibiotic resistance, a huge medical concern. Currently, the only available solutions against viruses are: vaccines that improve immunity to a particular disease (for example, the vaccine against human papilloma virus which causes cervical cancer); or antivirals that help treating human infections by stopping the virus from spreading into new cells (for example, acyclovir for cold sores or varicella).

 

Another myth around viruses is their reputation as pathogens. Yes, viruses can cause a disease, but some viruses are actually valuable to their host and can live in a symbiotic relationship with them. Research has shown that some viruses decrease the number of tumors in hamsters whereas others increase the survival of parasitic wasp eggs in insect larvae. Moreover, in humans it is known that viruses played a major part in the evolution of the placenta and that 8% of the genome is from viral origin. Finally, some viruses, especially those that infect bacteria (called bacteriophages), are currently being considered as a therapeutic option to control bacterial infections, such as ear or human skin infections, or to target cancer cells.

 

It is interesting to realize the importance of studying these microorganisms, as it can provide evidence about our surroundings, our history and life itself. Recently, some scientists discovered and resuscitated from ice a new type of virus that lived 30,000 years ago. This means that ice melts may trigger the return of other ancient viruses with potential traces of our past or with potential risks for human health. Regardless of what is to come, we have to continue seeking  truth and work towards abolishing myths because, as Kofi Annan said “knowledge is power”. It is crucial that we keep track of our knowledge as we develop and improve our technological capabilities and understanding of the world.

 

 

About the author: Natacha Ogando

 

Natacha is currently doing her PhD degree through the ANTIVIRALS project (a Marie Sklodowska Curie European Training Network) at Leiden University Medical Center in the Netherlands. She is trying to identify broad-spectrum coronavirus inhibitors and understand their mode of action. Besides, she likes to play football and goof around with her friends. She consider herself a citizen of the world and it is always planning new adventures to meet new cultures and new people.

 

Sources:

PNAS

- Retroviruses push the envelope for mammalian placentation (2012)

- Thirty-thousand-year-old distant relative of giant icosahedral DNA viruses with a pandoravirus morphology (2014)

Nature Reviews Microbiology

- The good viruses: viral mutualistic symbioses (2011)

- A century of the phage: past, present and future (2015)

Others

- Impact and effectiveness of the quadrivalent human papillomavirus vaccine: a systematic review of 10 years of real-world experience (2016)

- Aciclovir. A reappraisal of its antiviral activity, pharmacokinetic properties and therapeutic efficacy (1994)

- Inhibition of adenovirus oncogenicity in hamsters by adeno‑ associated virus DNA (1981)

- Virus in a parasitoid wasp: suppression of the cellular immune response in the parasitoid’s host (1981)

 

 

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