Medical Publishing

5. Propagation

Viruses are spread from person to person, causing new cases of the disease. Many of them, as those responsible for influenza and measles, are transmitted by inhalation, through its dissemination in the infected droplets emitted by coughing and sneezing. Others, like those that cause diarrhea are spread by fecal-oral route. In other cases, the spread is through the bite of insects, such as yellow fever and arboviruses. Viral diseases may be endemic (specific to one area), affecting susceptible individuals, or epidemic, which appear in waves and attack much of the population. An example is the emergence of epidemic flu worldwide, almost always once a year.

6. Treatment

The treatments against viral infections are often not entirely satisfactory, since most of the drugs that kill viruses also affect cells in which they play. The alpha-adamantanamine is used in some countries to treat respiratory infections caused by influenza A and isatin-beta-thiosemicarbazone, effective against smallpox. Certain substances similar to precursors of nucleic acids may be useful against severe herpes infections.

One promising antiviral agent is interferon, which is a non-toxic protein produced by some animal cells infected with viruses and can protect other cells against such infections. Is currently studying the effectiveness of the drug to fight cancer. Until recently, these studies were limited by their limited availability, but new techniques of cloning the genetic material, produce large amounts of this protein. In a few years you may know whether interferon is really effective as an antiviral agent.

The only effective way to prevent viral infections is the use of vaccines. Vaccination against smallpox worldwide in the 1970s, eradicated the disease. It has developed many human virus vaccines and other animals. Among infections suffered by people include measles, rubella, polio and influenza. Immunization with an antiviral vaccine stimulates the body’s immune mechanism, which produces antibodies that protect you when you return to contact with the same virus. Vaccines contain viruses always altered so they can not cause disease.

7. Infections in plants

The virus originated wide variety of plant diseases and serious damage to crops. The most common are produced by the virus of turnip yellow mosaic, the potato virus X (potato) and snuff mosaic virus. Plants have rigid cell walls that viruses can not cross, so that the most important for propagation is provided by the animals that feed on them. Often, insects inoculated into healthy plants that carry the virus on its mouth parts, from other infected plants. Also nematodes, roundworms can transmit the infection when they feed on the roots.

Plant viruses can accumulate huge amounts within infected cells. For example, the snuff mosaic virus may represent up to 10% of the dry weight of the plant. Studies of the interaction between virus and host cells are limited because the infection is via an insect vector. Also, do not typically available in the laboratory of cell cultures susceptible to infection by plant viruses.

credit to: Martín Buczyner