Dengue Viruses Cause Dengue Fever

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Viruses are the smallest in size but highly efficient infection machines. They are neither classified as living nor non-living. Viruses are relatively smarter at molecular levels. They can have both the deoxyribonucleic acid and ribonucleic acid and their various forms as genetic material. Moreover, viruses have a remarkable ability to invade a wide range of living organisms, from bacteria and plants to animals. The dengue, like other viruses, thrives only within a host.

 

The Discovery of Dengue Viruses

The dengue viruses belong to the genus Flavivirus within the Flaviviridae family. This group also includes other mosquito- and tick-borne viruses responsible for significant human diseases, such as yellow fever, West Nile, and Japanese encephalitis. The journey of discovering the dengue virus began in 1943, when Ren Kimura and Susumu Hotta isolated it while studying blood samples from patients during a dengue epidemic in Nagasaki, Japan. The following year, Albert B. Sabin and Walter Schlesinger independently achieved the same isolation, identifying what we now know as dengue virus 1 (DEN-1). However, DEN-1 is just one piece of the puzzle.

 

The Four Dengue Serotypes and May Be Others

Now we know that besides DEN-1, there are three others, DEN-2, DEN-3, and DEN-4, causing dengue fever. These are serotypes due to their distinct interactions with human blood serum antibodies. These serotypes exhibit genetic variations despite sharing around 65% of their genomes. Nevertheless, infection with any dengue serotype leads to similar clinical symptoms. Initially, DEN-1 and DEN-2 were in Central America and Africa, whereas all four serotypes were prevalent in Southeast Asia by the 1970s. By 2004, the distribution had broadened significantly, with all four serotypes circulating worldwide in tropical and subtropical regions and spreading to many other countries.

 

Understanding the Dengue Virus Structure

The dengue virus genome is a single strand of positive-sense RNA, directly translatable into proteins. This genome encodes ten genes, producing three structural proteins (capsid, envelope, and membrane) and seven nonstructural proteins crucial for viral replication and assembly. The virus is roughly spherical, about 50 nanometers in diameter, with a nucleocapsid core surrounded by a lipid bilayer membrane derived from the host, embedded with an envelope and

 

Viral Replication

The dengue virus embarks on a complex replication process upon entering the human body. It first attaches to a human skin cell, which engulfs the virus in an endosome. Deep within the cell, the acidic and negatively charged environment allows the virus to fuse with the endosomal membrane, releasing the nucleocapsid into the cytoplasm. Here, the viral RNA hijacks the host's machinery to replicate and produce viral proteins. These newly formed viral particles mature within the host's Golgi apparatus before being released to infect other cells, perpetuating the cycle.