Viral infection

Virus is Latin for poison. There is no original plural form of virus, so both virus and vira can be used in the plural form. The "virus" expression originates from before the term microorganisms were known and was used for all substances regarded as a cause of disease.
A virus consists of its hereditary material (DNA and RNA) surrounded by a protein integument. In the case of bacteria, they can usually be seen in a microscope at 1000 magnification, whereas vira require an electron microscope in order to be seen. A picorna virus (which causes polio and cold) has a size of about 20 millionths of a millimetre (20 nanometres). One of the largest vira is the pox virus (which causes variola). It is 120 - 300 nm. in size.
Strictly speaking, vira are not part of the generic term of microorganisms as they lack their own metabolism, and without a metabolism the ability to propagate independently is non-existing. Instead, vira invade living cells. This is the way it happens:
The virus clings to a host cell with receptors on its surface that fits the virus. This causes the cell to let viral DNA or -RNA pass through its cell wall and this causes the viral hereditary material to be built into the DNA of the host cell. The host cell will start to produce new vira which can invade new, healthy cells. In some cases the host cell dies when it has produced new vira, in other cases it lives on.
Arbo virus (Arthropod-Borne Virus)
Are transmitted via various insects (arthropods); e.g. mosquitoes and ticks. The diseases – with the exception of Dengue fever – especially occur in animals and are transmitted from the animals via e.g. mosquitoes to people. Being infected with the arbo virus can result in the tropical diseases Dengue fever, Yellow fever, and Japanese encephalitis.
Dengue fever
Is an acute viral infectious disease with fever caused by the arbo virus of the flavivirus group which is transmitted via mosquito bites from a certain kind of mosquito (Aedes aegypti) which is active very early in the morning and late in the afternoon. There are 4 different kinds of dengue fever and being infected with one does not give antibody protection against the other three. It is therefore possible to be infected with dengue fever more than once.
The disease causes flu-like symptoms with fever, violent headaches, joint- and muscle pain (breakbone pains), skin rashes spreading to the entire body, plus fatigue. Only rarely – and mostly among the local population – skin bleedings and shock may appear.
From being bitten by the infected mosquito until acute high fever occurs, most often 4 - 10 days pass. The fever rarely lasts for more than a week and in most cases, the disease is over in 10 days although subsequent the tiredness and possibly depression might last for weeks.
Serious reactions can occur in people who have previously been infected with one type of dengue virus and are now being infected with one of the other three. These serious variations of the disease are called dengue haemmoragic fever and dengue shock syndrome.
In dengue haemmoragic fever, bleedings areis which are caused by the destruction of blood platelets and the damage of blood vessels. In case of dengue shock syndrome, circulatory arrest occurs because the blood seeps out of the destroyed blood vessels and into the surrounding tissue.
The disease is often observed in youngsters, elderly, and weak persons and can be deadly.
The risk zone is especially cities in Central- and South America, India, the Pacific Island, and South East Asia where there the incidence is high.
Ebola fever
The viral disease only occurs in Africa and is actually quite rare. It was discovered quite recently and is a deadly disease caused by the Ebola virus transmitted via the bodily fluids of infected people.
The virus attacks both the cells, organs, and tissues in the body. The actual disease starts 3 - 21 days after contamination and the first symptoms are fever, shivers, and soreness; after that the symptoms develop into diarrhoea, violent chest- and stomach pains, and conjunctivitis. Moreover, the disease can cause bleedings leading to shock and eventually death. The death-rate is very high.
Yellow fever (Febris flava)
Is a viral disease caused by an arbo virus transmitted between people (and apes) via mosquitoes. Some infections have an easy course and feels like a heavy case of the flu, but the disease can become serious. The symptoms are fever, headaches, nausea, stomach pains, vomiting, back pains, and an exhausting fatigue. After a short improvement, bloody vomitings and violent hepatitis might occur.
The disease can have chronic consequenses as it might attack the kidneys, brain, and heart and cause kidney- and liver failure plus bleedings from the mucous membranes. When suffering from liver failure the skin, mucous membranes, and the white of the eyes are coloured yellow and this is what has given the disease its name.
Yellow fever occurs in the tropic part of Africa and in South America in the area 15 degrees north and 15 degrees south of Equator.

Rabies is a fatal viral disease (Rhabdoviridae from the Lyssa virus group) that infects mammals such as apes, bats, cats, cows, dogs, foxes, raccoons, reindeer, sheep, skunks, and wild rodents, who might again infect humans. The rabies virus is present in the infected animal’s saliva and is transmitted via the saliva when the infected animal bites, scratches, or licks another animal or a human.
Rabies attacks the central nervous system and the first symptoms are therefore an altered behaviour.
The unnatural behaviour of an infected animal could e.g. be a wild animal's loss of shyness, an unusual aggression, confusion, or a shifty and reserved behaviour. The animal often has foam arond its mouth and it is unable to swallow, eat, and drink since the consumption of liquid causes painful cramps in the neck, back, and throat. The incubation period can be anything from a few days and up to several years after a bite, but normally it is 3-12 weeks.
The area around the bite will be painful, and later pain is accompanied by fever, confusion, hallucinations, headache, shivers, and hypersensitivity to light, and maybe even later on aggressiveness. After these symptoms cramps, paralysis, and extreme hydrophobia occur. The last thing because of the painful muscle contractions occuring when the sick person drinks water. Later on the hydrophobia develops into occuring at just the sound, sight, or splash of water. Often the patient dies during a cramp attack within 10 days of the outbreak and he or she suffers terribly until death occurs.
It varies as to which mammals are infected in the different countries. The disease is widespread in the entire world – especially in Africa, Asia, Greenland, North-, Central-, and South America, Central-, South-, and Eastern Europe. Approximately 15,000 people die every year on account of this disease.
Japanese encephalitis
Is caused by a flavi virus from the arbo virus group transmitted by various kinds of mosquitoes that bite both day and night. The virus is transmitted to animals such as pigs and to certain birds and from there to humans. One is most exposed in rural and humid areas with rice fields and in the rainy season. The disease is present in large parts of Asia: Bali, India, China, and Nepal.
The incubation period is 5 - 20 days. The symptoms are usually mild to high fever, confusion, violent headache, and pain behind the eyes. Moreover, cramps, and maybe paralysis and loss of consciousness occur. Not everyone who is infected gets the actual disease; one in 200 patients develops the actual encephalitis that might be deadly.
The acute period might last up to several weeks. Among the survivors of the disease, 30 - 40% might have lasting and disabling mental injuries. The most dangerous viral meningitises are caused by e.g. Japanese encephalitis. See "Viral meningitis" below.
Lassa fever
The disease only occurs in rural areas in Africa - the risk of infection is especially large in Nigeria, Sierra Leone, and Western Africa. It was discovered relatively recently and is a deadly and very infectious viral disease caused by the arena virus that is infectious via the urine of rats.
The symptoms of Lassa fever might be mistaken for a whole lot of other viral diseases. For this reason, the diagnosis is made on the basis of indications. The fever disease begins as a serious flu with fever, headache, shivers, and soreness.
After this, symptoms occur such as diarrhoea, vomiting, chest pains, and a soar throat with the formation of wounds. Recovery is very slow, and if surviving the disease a feeling of exhaustion will be present for several weeks. Weak people get very ill and often break down shortly after the appearance of the first symptoms which might cause loss of consciousness and death.
The marburg disease
Was discovered quite recently and is a deadly viral infection caused by the marburg virus that is present only in Africa.
Originally, it stems from infected laboratory apes. The symptoms resemble a very bad case of the flu. A scaling measle-like rash might occur. After this, there may be bleedings from mucous membranes, the skin, the stomach, and the intestines. The death-rate is high.
Polio (infantile paralysis)
Is caused by the polio virus types 1, 2, and 3 that is contagious via drop infection and through contaminated water and/or food. The symptoms are fever, headache, and stiffness in the neck and back. Moreover paralysis might occur. The prevalence of the disease is highest in the developing countries - but it occurs in a few European countries as well. The most dangerous viral meningitises are caused by e.g. Polio. See "Viral meningitis" below.
Viral meningitis
The disease can occur on account of quite a lot of vira, e.g. mumps, measles, and rubella. The most dangerous viral meningitises are caused by Japanese encephalitis and Polio.