Negative-strand RNA virus

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A negative-strand RNA virus (or negative-sense RNA virus) is a type of RNA virus whose genetic material is single-stranded RNA that is complementary to the mRNA (messenger RNA) needed for protein synthesis. This means that the viral RNA must be transcribed by an RNA-dependent RNA polymerase to produce a positive-sense RNA strand that can be translated by the host cell's ribosomes.

Classification

Negative-strand RNA viruses are classified within the order Mononegavirales, which includes several families:

• Bornaviridae: This family includes viruses that primarily infect mammals and are known to cause neurological diseases.
• Filoviridae: This family includes the Ebola virus and Marburg virus, which are known for causing severe hemorrhagic fevers.
• Mymonaviridae: A relatively newly identified family of viruses.
• Nyamiviridae: Another family of viruses with various hosts.
• Paramyxoviridae: This family includes viruses such as the measles virus and mumps virus, which are significant human pathogens.
• Pneumoviridae: This family includes the respiratory syncytial virus (RSV), which is a major cause of respiratory infections in infants and young children.
• Rhabdoviridae: This family includes the rabies virus, which is known for causing fatal encephalitis in mammals.

Replication Cycle

The replication cycle of negative-strand RNA viruses involves several key steps:

1. Attachment and Entry: The virus attaches to the host cell surface via specific receptors and enters the cell through endocytosis or membrane fusion. 2. Transcription: The viral RNA-dependent RNA polymerase transcribes the negative-sense RNA genome into positive-sense mRNA. 3. Translation: The positive-sense mRNA is translated by the host cell's ribosomes to produce viral proteins. 4. Replication: The viral RNA polymerase replicates the viral genome to produce new negative-sense RNA strands. 5. Assembly and Release: New viral particles are assembled and released from the host cell, often causing cell lysis or budding off from the cell membrane.

Pathogenesis

Negative-strand RNA viruses are responsible for a wide range of diseases in humans and animals. They can cause respiratory infections, neurological diseases, and hemorrhagic fevers, among other conditions. The severity of the disease depends on the specific virus and the host's immune response.

Research and Treatment

Research on negative-strand RNA viruses focuses on understanding their replication mechanisms, pathogenesis, and interactions with the host immune system. This knowledge is crucial for developing antiviral drugs and vaccines. For example, vaccines have been developed for diseases caused by viruses in the Paramyxoviridae family, such as measles and mumps.

See Also

• Positive-strand RNA virus
• RNA virus
• Virus classification
• Viral replication