Alpha, Beta and Gamma

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A virus is a microscopic entity composed of genetic material (DNA or RNA) enclosed within a protein coat. Viruses are extremely small, measuring only a few nanometers across (one billionth of a meter).

Unlike bacteria, viruses are not cellular structures; they lack a membrane, cytoplasm, or nucleus. Their simplicity raises the debate over whether they are truly "alive." The primary biological activity of viruses is reproduction, which they can only achieve by infecting a host cell. In contrast, bacteria are independent organisms capable of reproducing on their own.

Viruses are highly diverse and can infect a wide range of organisms and cell types. Some viruses target human cells and cause diseases. Notable examples include the Epstein-Barr virus (EBV), which causes glandular fever, and the human papillomavirus (HPV), which can lead to cervical cancer.