What is the Difference Between Enveloped and Non-enveloped Viruses

The main difference between enveloped and non-enveloped viruses is that enveloped viruses contain a lipid bilayer membrane on the outer part of the virus, whereas non-enveloped viruses do not contain a lipid bilayer membrane on the outer part of the virus.  

Enveloped and non-enveloped viruses are two virus types classified depending on the presence of an envelope.      

Key Areas Covered

1. What are Enveloped Viruses
– Definition, Features, Importance
2. What are Non-enveloped Viruses
– Definition, Features, Importance
3. Similarities Between Enveloped and Non-enveloped Viruses
– Outline of Common Features
4. Difference Between Enveloped and Non-enveloped Viruses
– Comparison of Key Differences

Key Terms 

Enveloped Viruses, Non-enveloped Viruses

What are Enveloped Viruses

Enveloped viruses are a type of viruses that contain an envelope surrounding the nucleocapsid. It is a lipid bilayer, forming the outer part of the virus. A key feature of the enveloped viruses is their virulence. Significantly, enveloped viruses are less virulent because they do not undergo cell lysis during their exit from the cell, although viral replication is always followed by cell death. Due to the containment of the viral envelope made up of a lipid bilayer, the virus uses the host’s cell membrane during the assembly as the envelope. It allows the viral particles to exit without breaking the host cell’s cell membrane. The process is called cell lysis.

Figure 1: Enveloped Virus

Furthermore, enveloped viruses can escape the host’s immune system. Since the lipid bilayer makes up the virus’s envelope, the immune system does not recognize the viral particles. However, enveloped viruses are more sensitive to harsh environmental conditions such as extreme pH, dryness, heat, and simple disinfectants. Influenza, human cytomegalovirus (HCMV), HIV, respiratory syncytial virus (RSV), vaccinia virus, and human coronaviruses (such as NL63, 229E, OC43, and SARS-CoV-2) are examples of enveloped viruses. 

What are Non-enveloped Viruses

Non-enveloped viruses are viruses that only contain a viral genome and a capsid. Therefore, they do not contain an envelope or a lipid bilayer surrounding the virus’s capsid. Hence, non-enveloped viruses are also called naked viruses. Typically, they are more virulent than the enveloped viruses because they undergo cell lysis. Following the replication of the viral particles inside the host cell, they undergo cell lysis, releasing the viral particles outside the host cell. It means they break up the host cell membrane. Also, cell lysis causes the host cell death by violating the integrity of the cell membrane.

Figure 2: Norovirus

Moreover, non-enveloped viruses are more resistant to harsh environmental conditions such as extreme pH, dryness, heat, and simple disinfectants. Norovirus, enterovirus, adenovirus, and rhinovirus are examples of non-enveloped viruses.   

Similarities Between Enveloped and Non-enveloped Viruses

• Enveloped and non-enveloped viruses are two virus types.
• They are classified according to the presence of an envelope.
• They contain a capsid and genetic material. 

Difference Between Enveloped and Non-enveloped Viruses

Definition

Enveloped viruses refer to viruses that contain a viral envelope, the outermost layer of many types of viruses. In contrast, non-enveloped viruses refer to viruses containing only the viral genome and the virus-coded proteins. 

Envelope

Enveloped viruses contain an envelope, a lipid bilayer membrane on the outer part of the virus, while non-enveloped viruses do not contain an envelope.    

Virulence

Enveloped viruses are less virulent, while non-enveloped viruses are more virulent.  

Environmental Conditions

Enveloped viruses are less resistant to harsh environmental conditions, while non-enveloped viruses are more resistant. 

Viral Replication

Enveloped viruses do not undergo cell lysis, while non-enveloped viruses undergo cell lysis. 

Examples

Influenza, human cytomegalovirus (HCMV), HIV, respiratory syncytial virus (RSV), vaccinia virus, and human coronaviruses (such as NL63, 229E, OC43, and SARS-CoV-2) are examples of enveloped viruses. At the same time, norovirus, enterovirus, adenovirus, and rhinovirus are examples of non-enveloped viruses.   

Conclusion

In brief, enveloped and non-enveloped viruses are two virus types that occur in the environment. Enveloped viruses contain an envelope, a lipid membrane on the outer part of the virus. Therefore, they are less virulent and less resistant to harsh environmental conditions. Also, they do not undergo cell lysis. In comparison, non-enveloped viruses do not contain an envelope. Hence, they are more virulent and more resistant to harsh environmental conditions. But they undergo cell lysis. So, the main difference between enveloped and non-enveloped viruses is the presence of an envelope.  

References:

1. Viral envelope. Viral Envelope – an overview | ScienceDirect Topics. (n.d.-a). https://www.sciencedirect.com/topics/immunology-and-microbiology/viral-envelope
2. Naked virus – definition and examples – biology online dictionary. Biology Articles, Tutorials & Dictionary Online. (2022, June 16). https://www.biologyonline.com/dictionary/naked-virus

Image Courtesy:

1. “Simple diagram of virus (en)” By domdomegg – Own work (CC-BY 4.0) via Commons Wikimedia
2. “Norovirus 4” By en:User:Graham Beards – Own Work (CC-BY 3.0) via Commons Wikimedia