Viruses occupy a unique biological space, sitting on the boundary between living and non-living entities. Unlike bacteria or fungi, a virus is not a complete cell. It is an obligate intracellular parasite, meaning it completely lacks the metabolic machinery required to generate energy or synthesize proteins on its own. To survive and multiply, a virus must hijack the living machinery of a host cell. In Nigerian clinical practice, midwives encounter numerous viral pathogens that threaten maternal and neonatal health, including the human immunodeficiency virus (HIV), hepatitis B virus, measles, and rubella. Understanding their basic nature helps explain why standard antibacterial drugs like penicillin are completely useless against viral infections.
A complete, infectious viral particle is called a virion. At its core lies the genetic material, which can be either DNA or RNA, but never both in the same virus. Surrounding this genetic core is a protective protein coat known as a capsid, built from smaller protein subunits called capsomeres. Together, the nucleic acid and the capsid form the nucleocapsid.
Some viruses possess an outer covering called an envelope, which is derived from the host cell membrane during release. Enveloped viruses, such as HIV and herpes simplex, are generally more vulnerable to heat, drying, and alcohol-based disinfectants because their outer lipid membrane easily breaks down. Naked viruses lack this envelope and tend to survive much longer in the environment.
Classifying viruses helps clinicians understand how they spread and cause disease. Unlike bacteria, viruses are not classified using a binomial genus and species name in the traditional sense. Instead, modern virology relies heavily on the Baltimore classification system, which groups viruses based on their type of nucleic acid (DNA or RNA) and their method of messenger RNA synthesis.
Key groups include:
Viral multiplication follows a strict biological sequence inside a susceptible host cell. Midwives should understand these phases because many antiviral medications are designed to block specific steps in this cycle.
When viruses multiply inside human tissues, they cause noticeable cellular damage known as cytopathic effect (CPE). Some infections lead to rapid cell death and tissue breakdown, as seen in acute viral illnesses. Other viruses establish persistent or latent infections where the viral genome remains inside the host cell for years without causing immediate destruction, occasionally reactivating under stress, such as the Herpes Simplex Virus. In some cases, viral integration into host chromosomes can disrupt normal cell cycle controls, leading to uncontrolled cellular proliferation and malignant transformation, which is how human papillomavirus (HPV) can eventually lead to cervical cancer.