Herpes simplex type 1 (HSV‑1) is a widespread pathogen responsible for orolabial lesions. It is an enveloped, double-stranded DNA (dsDNA) virus belonging to the family Herpesviridae. Once the virus infects a host cell, its double‑stranded DNA genome is delivered into the nucleus, where a coordinated cascade of immediate‑early, early, and late gene expression directs viral DNA replication, structural protein synthesis, and virion assembly. After primary infection of epithelial cells, HSV-1...

Poliomyelitis is caused by poliovirus, a small, non-enveloped, positive-sense RNA virus of the Picornaviridae family and Enterovirus genus. Transmission occurs primarily via the fecal-oral route, often through ingestion of contaminated water or food. The virus initially replicates in the oropharynx and intestinal mucosa, particularly in lymphoid tissues such as the tonsils, Peyer’s patches, and regional lymph nodes. Primary viremia follows, allowing dissemination throughout the body.In most...

Rabies is a lethal zoonotic disease caused by a single-stranded, negative-sense RNA virus of the Lyssavirus genus, within the family Rhabdoviridae. Its primary mode of transmission to humans is through bites or saliva-contaminated scratches from infected mammals such as dogs, bats, raccoons, or foxes. Transmission can also occur if infectious saliva contacts abraded skin or intact mucous membranes, including the conjunctiva.Viral Entry and Early ReplicationOnce introduced at the bite or scratch...

Yellow fever is a viral hemorrhagic disease caused by the yellow fever virus (YFV), a member of the Flaviviridae family. It is transmitted primarily by Aedes and Haemagogus mosquitoes in tropical and subtropical regions of Africa and South America. After transmission through a mosquito bite, the virus initially replicates in skin-resident immune cells such as dendritic cells and macrophages. These cells then migrate to the lymph nodes, where viral replication increases, eventually leading to...

Cytomegalovirus (CMV) disease is caused by human cytomegalovirus, a double-stranded DNA virus of the Herpesviridae family. While primary CMV infection is often asymptomatic in immunocompetent individuals, the virus can cause severe disease in neonates and immunocompromised patients. CMV is the most common cause of congenital viral infection in the United States, and a major pathogen in solid organ and hematopoietic stem cell transplant recipients.CMV is transmitted via bodily fluids, sexual...

Genital herpes is a sexually transmitted infection primarily caused by herpes simplex virus type 2 (HSV-2), though herpes simplex virus type 1 (HSV-1) is increasingly implicated in genital infections, particularly among younger populations. Transmission occurs mainly through sexual contact, with asymptomatic viral shedding serving as a major route of spread. This characteristic makes HSV-2 difficult to control at a population level, as individuals may unknowingly transmit the virus even in the...