Difference Between Enveloped and Nonenveloped Viruses

The key difference between enveloped and nonenveloped viruses is that enveloped viruses possess a lipid bilayer surrounding the protein capsid, while nonenveloped viruses lack this lipid bilayered membrane.

Viruses are tiny infectious particles that show living as well as non-living characteristics. Virus particles have two main components: the viral genome and the protein capsid. Protein capsid surrounds the viral genome. Some viruses have another cover called envelope surrounding the protein capsid. Envelope constitutes of a lipid bilayer. Moreover, it contains viral proteins that are essential in binding with the host cells. Protein capsid and envelope play key roles in viral infection including virus attachment to host cell, entry into the cell, release of the proteins of the capsid, assembly and packaging of newly synthesized viral particles, transfer of the viral genetic material from one cell to another, etc. However, only enveloped viruses possess an envelope.

CONTENTS

1. Overview and Key Difference
2. What are Enveloped Viruses
3. What are Nonenveloped Viruses
4. Similarities Between Enveloped and Nonenveloped Viruses
5. Side by Side Comparison – Enveloped vs Nonenveloped Viruses in Tabular Form
6. Summary

What are Enveloped Viruses?

Some viruses have an extra lipid membrane called envelope surrounding the protein capsid. These viruses belong to the virus group named ‘enveloped viruses’. The envelope contains phospholipids and proteins derived from host cell membranes. Enveloped viruses acquire this envelope during viral replication and release. HIV, HSV, HBV, and influenza virus are several examples of enveloped viruses. Moreover, some enveloped viruses contain spikes (made from glycoprotein) protruding from the envelope.

Viral proteins in the envelope help the virus to bind with the host cell receptors. Viral envelope plays a major role in viral infections, including host recognition and entry. It helps the virus for attachment, transfer of genetic material to host cell and between cells, etc. Moreover, some viral envelopes help in determining characteristics of viral stability, such as resistance to chemical and physical inactivation. Enveloped viruses are more sensitive to biocides. Furthermore, they are sensitive to heat, dryness and acids.

What are Nonenveloped Viruses?

Nonenveloped viruses are the viral particles composed only of nucleocapsids. They lack the lipid membrane or the envelope. Since they don’t have an envelope, we call them naked viruses. Nonenveloped viruses are more virulent compared to enveloped viruses because they often cause host cell lysis. Furthermore, nonenveloped viruses are resistant to heat, dryness and acids. They can even survive in the gastrointestinal tract of mammals.

Moreover, they can tolerate harsh environmental conditions. Norovirus, parvovirus, HEV, HAV are several examples of nonenveloped viruses.

What are the Similarities Between Enveloped and Nonenveloped Viruses?

• Both enveloped and nonenveloped viruses have nucleocapsid.
• Also, they contain a viral genome.
• Moreover, both types cause diseases to different living organisms.
• They need a host to replicate. Hence, they are obligate parasites.

What is the Difference Between Enveloped and Nonenveloped Viruses?

Enveloped viruses and nonenveloped viruses are two groups of viruses categorized based on the presence or absence of lipid bilayer with proteins. Enveloped viruses have a lipid bilayer called envelope surrounding the protein capsid while nonenveloped viruses do not have it. So, this is the key difference between enveloped and nonenveloped viruses.

Furthermore, nonenveloped viruses are more virulent than enveloped viruses. They cause host cell lysis, unlike enveloped viruses. Therefore, we can consider this as another difference between enveloped and nonenveloped viruses.

The below infographic summarizes the difference between enveloped and nonenveloped viruses comparatively.

Summary – Enveloped vs Nonenveloped Viruses

Based on the presence and absence of an envelope, there are two groups of viruses as enveloped viruses and non-enveloped viruses (naked viruses). Here, the naked viruses do not contain an envelope surrounding the nucleocapsid. So, this is the key difference between enveloped and nonenveloped viruses. Compared to enveloped viruses, naked viruses can survive a long time in the environment. Moreover, nonenveloped viruses are more virulent than enveloped viruses. They often cause host cell lysis. But, enveloped viruses are often released by budding rather than cell lysing.

Reference:

1. “Viral Envelope.” Wikipedia, Wikimedia Foundation, 30 Nov. 2018, Available here.
2. Gelderblom, Hans R. “Structure and Classification of Viruses.” Medical Microbiology. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1996, Available here.

Image Courtesy:

1. “HI-virion-structure” By Thomas Splettstoesser (www.scistyle.com) – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Non-enveloped helical virus” By Nossedotti (Anderson Brito) – Own work (CC BY-SA 3.0) via Commons Wikimedia