The yellow fever virus is transmitted by the bite of female mosquitoes and is found in tropical and subtropical areas in South America and Africa, not in Asia. Since the 17th century, several major epidemics of the disease have been recorded in the Americas, Africa and Europe. In the 19th century, yellow fever was deemed one of the most dangerous infectious diseases. Yellow fever begins after an incubation period of three to six days. Most cases only cause a mild infection with fever, headache, chills, back pain, loss of appetite,...
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West Nile virus is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, crows, robins, crocodiles and alligators. The main route of human infection is through the bite of an infected mosquito. The West Nile Virus produces one of three different outcomes in humans. The first is an asymptomatic infection (approximately 90% of West Nile Virus infections in humans are without any symptoms); the second is a mild febrile syndrome termed West Nile...
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The variola virus includes several strains, all of which cause various "pox" diseases with the most famous one being Smallpox. Variola caprina is the virus that causes goatpox, and Variola porcina is the virus that causes swinepox. Variola major and minor are the famously known viruses that caused the highly contagious, epidemic (now considered nearly extinct) of smallpox. The term "smallpox" was first used in Europe in the 15th century to distinguish variola from the "great pox" (syphilis). The disease killed an estimated 400,000 Europeans per year during the closing...
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Rubella, commonly known as German measles, is a disease caused by the rubella virus. Rubella is a common childhood infection usually with minimal systemic upset although transient arthropathy (joint condition) may occur in adults who contract the virus. Serious complications are very rare, although infection of a pregnant woman by Rubella virus can be serious. If the mother is infected within the first 20 weeks of pregnancy, the child may be born with congenital rubella syndrome (CRS), which entails a range of serious illnesses. Spontaneous abortion occurs in up to...
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Rotavirus is the most common cause of severe diarrhea among infants and young children, accounting for close to 50% of hospitalizations for that. It is one of several viruses that cause infections often called stomach flu, despite having no relation to influenza. Rotavirus A, the most common of the 5 known species, causes more than 90% of infections in humans. Worldwide nearly 500,000 children under five years of age still die from rotavirus infection each year and almost two million more become severely ill. In addition to its impact on...
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Human rhinoviruses are the most common viral infective agents in humans and are the predominant cause of the common cold. There are two modes of transmission: aerosols of respiratory droplets and contaminated surfaces, including direct person-to-person contact. Human rhinoviruses occur worldwide. Symptoms include sore throat, runny nose, nasal congestion, sneezing and cough. They may also be accompanied by muscle aches, fatigue, malaise, headache, muscle weakness, or loss of appetite. Fever and extreme exhaustion are more common in influenza. In the United States, the incidence of colds is higher in the...
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Human respiratory syncytial virus (RSV) is a virus that causes respiratory tract infections. It is the major cause of lower respiratory tract infections and results in many hospital visits during infancy and childhood. In temperate climates there is an annual epidemic during the winter months. In tropical climates, infection is most common during the rainy season. In the United States, 60% of infants are infected during their first RSV season, and nearly all children will have been infected with the virus by 2–3 years of age. Among those infected with...
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Rabies is a viral disease that causes acute encephalitis (inflammation of the brain). It is zoonotic (i.e., transmitted by beasts), most commonly by a bite from an infected subject. Roughly, ninety-seven percent of human rabies cases come from dog bites. The rabies virus travels to the brain by following the peripheral nerves. The incubation period of the disease is usually a few months in humans, depending on the distance the virus must travel to reach the central nervous system. The time between infection and the first flu-like symptoms is normally...
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The B19 virus, generally referred to as parvovirus B19 or sometimes erythrovirus B19, causes a childhood rash called fifth disease or erythema infectiosum, which is commonly called "slapped cheek syndrome". You can see why by the photo. The virus is primarily spread by infected respiratory droplets, but blood-borne transmission has been reported. Fifth disease or erythema infectiosum is only one of several expressions of Parvovirus B19. Any age may be affected, although it is most common in children aged six to ten years. It is named due to being the...
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HPIVs (human parainfluenza viruses) are spread person to person by direct contact with infected secretions through respiratory droplets or contaminated surfaces or objects. Infection can occur when infectious material contacts mucous membranes of the eyes, mouth, or nose, and possibly through the inhalation of droplets generated by a sneeze or cough. HPIVs can remain infectious in airborne droplets for over an hour. HPIVs are ubiquitous and infect most people during childhood. The highest rates of serious HPIV illnesses occur among young children. Serologic surveys have shown that 90-100% of children...
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Human papillomaviruses (HPV) establish productive infections either in keratinocytes of the skin (outermost layer of the skin, causing warts) or in mucous membranes, as in the case of HPV. HPV is the most frequent sexually transmitted disease in the world! These viruses are responsible for common warts, plantar warts, flat warts and possibly the cause of many skin tags. More than 30 to 40 types of HPV are typically transmitted through sexual contact and infect the anal-genital region. Some sexually transmitted HPV types may cause genital warts. Persistent infection with...
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