Influenza Virus, Epidemiology, and Malaria

Posted on Mar 15, 2025 in Microbiology

The Lytic Life Cycle of the Influenza Virus

The lytic cycle is a method of viral replication involving the independent replication of viral DNA/RNA as part of virion assembly.

This is in contrast to the lysogenic cycle, where the viral DNA is integrated into the host genome and replicated with the cell’s DNA.

The lytic life cycle of the influenza virus can be summarized in a number of key steps:

When the virus attaches to cell surface receptors, it is internalized in an endosome, uncoated, and released into the cytoplasm.
Influenza is a retrovirus, and the RNA of the viral genome is transported to the nucleus where it is replicated (reverse transcription is not involved).
The viral RNA acts as an mRNA template for the translation of viral core proteins, which assemble as a capsid around viral RNA in the cytoplasm.
Newly constructed virus particles recognize regions of the cell membrane where viral proteins have attached and are released from these points.
Unlike most lytic viruses, the influenza virus does not promote the lysis of the cell as part of its release.

Epidemiology is the study of the occurrence, distribution, and control of diseases.

A pandemic is an outbreak of a disease over a large geographical area (i.e., many countries).

In the late 20th century (1997), there was a pandemic outbreak of avian bird flu.

Infectious Agent: The outbreak was caused by the H5N1 virus.
Mode of Transmission: The virus originated in domestic poultry but spread to humans through exposure to the birds and their feces.
Distribution: The outbreak originated in Asia, and although it mainly remained there, there were cases noted in other parts of the world.
Methods of Control: Containment strategies were employed for the infected, infected birds were killed, and global records of occurrences were kept.
Problems of Control: Migrating wild birds could spread the virus, problems coordinating international communities, and questions of equitable access to care.

Malaria is caused by the protozoan Plasmodium and is transmitted to humans by the Anopheles mosquito (females only).

The life cycle of the Plasmodium parasite requires both a primary human host (adult stage) and an intermediary mosquito host (juvenile stage).

When a mosquito ingests infected human blood, the parasite reproduces and matures in the mosquito’s gut before migrating to the salivary glands.
When a mosquito feeds on another human, the parasite is injected into the blood and travels to the liver for further development.
After a period, the parasite migrates to erythrocytes (red blood cells), which then rupture as the parasite spreads.
Symptoms of malaria include fever, nausea, and chills – these symptoms may be cyclic due to the parasitic life cycle (period of dormancy in the liver).
Additionally, the frequent rupturing of red blood cells can lead to the development of anemia.