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A viral infection does not always cause disease. A viral infection simply involves viral replication in the host, but disease is the damage caused by viral multiplication. [5] An individual who has a viral infection but does not display disease symptoms is known as a carrier. [17] Mechanisms by which viruses cause damage and disease to host cells
An example would include the ability of the herpes simplex virus, which causes cold sores, to remain in a dormant state within the human body. This is called latency [110] and is a characteristic of the herpes viruses, including Epstein–Barr virus, which causes glandular fever, and varicella zoster virus, which causes chickenpox and shingles.
Their growth and reproduction within their hosts can cause disease. "Germ" refers to not just a bacterium but to any type of microorganism, such as protists or fungi, or other pathogens that can cause disease, such as viruses, prions, or viroids. [1] Diseases caused by pathogens are called infectious diseases. Even when a pathogen is the ...
Viruses can, and do, turn our world upside down. But they also made us into what we are today.
In developing countries, viruses that cause respiratory and enteric infections are common throughout the year. Viruses carried by insects are a common cause of diseases in these settings. Zika and dengue viruses for example are transmitted by the female Aedes mosquitoes, which bite humans particularly during the mosquitoes' breeding season. [60]
Viruses, however, use a completely different mechanism to cause disease. Upon entry into the host, they can do one of two things. Many times, viral pathogens enter the lytic cycle; this is when the virus inserts its DNA or RNA into the host cell, replicates, and eventually causes the cell to lyse, releasing more viruses into the environment.
An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection. Infections can be caused by a wide range of pathogens, most prominently bacteria and viruses. [2] Hosts can fight infections using their immune systems.
[2] [3] Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. [4] [5] [6] Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. [7]