Parvovirus B19

Parvovirus B19
Electron micrograph of Parvoviruses in blood
Virus classification
Group: Group II (ssDNA) Family: Parvoviridae Genus: Erythrovirus Species: B19 virus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Parvovirus B19 (B19 virus) was the first (and, until 2005, only) human parvovirus to be discovered, by chance in 1975 by the Australian virologist Yvonne Cossart. It gained its name because it was discovered in well B19 of a large series of petri dishes apparently numbered in this way.

Electron micrograph of Parvoviruses in blood

Parvovirus B19 is best known for causing a childhood exanthem called fifth disease or erythema infectiosum.

Virology

The B19 virus belongs to the Parvoviridae family of small DNA viruses. It is classified as Erythrovirus because of its capability to invade red blood cell precursors in the bone marrow.

Transmission

The virus is primarily spread by infected respiratory droplets; blood-borne transmission, however, has been reported. The secondary attack risk for exposed household persons is about 50%, and about half of that for classroom contacts.

Infectivity

B19 symptoms begins some six days after exposure and last about a week. Infected patients with normal immune systems are contagious before becoming symptomatic, but probably not after then. Individuals with B19 IgG antibodies are generally considered immune to recurrent infection, but reinfection is possible in a minority of cases. About half of adults are B19-immune due to a past infection.

Epidemiology

A significant increase in the number of cases is seen every three to four years; the last epidemic year was 1998. Outbreaks can arise especially in nurseries and schools.

Parvovirus B19 causes an infection in humans only; cat and dog parvoviruses do not infect humans. In contrast with small animals, there is no vaccine available for human parvovirus B19.

Role in disease

Child showing symptoms of erythema infectiosum, or Fifth disease.

Fifth disease

Fifth disease or erythema infectiosium 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.

After being infected, patients usually develop the illness after an incubation period of four to fourteen days. The disease commences with fever and malaise while the virus is most abundant in the bloodstream, and patients are usually no longer infectious once the characteristic rash of this disease has appeared.

Teenagers or young adults tend to develop the so called 'Papular Pupuric Gloves and Socks Syndrome.' Unlike young children, these patients may be infectious with this rash.

Rash

The "slapped cheek" appearance typical of Fifths disease.

The rash of fifth disease is typically described as "slapped cheeks," with erythema across the cheeks and sparing the nasolabial folds, forehead, and mouth. Because of this rash, fifth disease is sometimes called slapped cheek syndrome. Fifth disease is also known for "lace-like" rashes on the arms, legs, torso, and back. These rashes can last for up to 5 weeks and are worse after sun exposure, exercise, or hot baths.

Arthritis

In adults (and perhaps some children), parvovirus B19 can lead to a seronegative arthritis which is usually easily controlled with analgesics. Women are approximately twice as likely as men to experience arthritis after parvo virus infection. Possibly up to 15% of all new cases of arthritis are due to parvovirus, and a history of recent contact with a patient and positive serology generally confirms the diagnosis. This arthritis does not progress to other forms of arthritis. Typically joint symptoms last 1-3 weeks, but in 10-20% of those affected, it may last weeks to months.

Aplastic crisis

Although most patients have an arrest of erythropoiesis (production of red blood cells) during parvovirus infection, it causes worse problems in patients with sickle cell anemia, or with hereditary spherocytosis, who are heavily dependent on erythropoeisis due to the reduced lifespan of the red cells. This is termed "aplastic crisis" (also called reticulocytopenia). It is treated with blood transfusion. Sickle-cell patients will probably be the first candidates for a parvovirus B19 vaccine when it is developed.

Hydrops fetalis

Parvovirus infection in pregnant women is associated with hydrops fetalis due to severe fetal anemia, sometimes leading to miscarriage or stillbirth. The risk of fetal loss is about 10% if infection occurs before pregnancy week 20 (esp. between weeks 14-20), but minimal after then. Routine screening of the antinatal sample would enable the pregnant mother to determine the risk of infection. Knowledge of her status would allow the mother to avoid the risk of infection.The risk to the fetus will be reduced with correct diagnosis of the anemia (by ultrasound scans) and treatment (by blood transfusions). Once the baby is born, there is evidence to suggest that no developmental abnormalities are due to B19 infection during pregnancy.

Differentiating Parvovirus B19 Rash from other diseases

Different rash-like conditions may be misdiagnosed with the rash from Parvovirus B19, including:

• Insect bites - In an insect bite, the insect injects formic acid, which can cause an immediate skin reaction often resulting in a rash and swelling in the injured area, often with formation of vesicles.

• Kawasaki disease - commonly presents with high and persistent fever, red mucous membranes in mouth, "strawberry tongue", swollen lymph nodes and skin rash in early disease, with peeling off of the skin of the hands, feet and genital area.

• Measles - commonly presents with high fever, coryza and conjunctivitis, with observation of oral mucosal lesions (Koplik's spots), followed by widespread skin rash.

• Monkeypox - presentation is similar to smallpox, although it is often a milder form, with fever, headache, myalgia, back pain, swollen lymph nodes, a general feeling of discomfort, and exhaustion. Within 1 to 3 days (sometimes longer) after the appearance of fever, the patient develops a papular rash, often first on the face. The lesions usually develop through several stages before crusting and falling off.

• Rubella - commonly presents with a facial rash which then spreads to the trunk and limbs, fading after 3 days, low grade fever, swollen glands, joint pains, headache and conjunctivitis. The rash disappears after a few days with no staining or peeling of the skin. Forchheimer's sign occurs in 20% of cases, and is characterized by small, red papules on the area of the soft palate.

• Atypical measles - symptoms commonly begin about 7-14 days after infection and present as fever, cough, coryza and conjunctivitis. Observation of Koplik's spots is also a characteristic finding in measles.

• Coxsackievirus - the most commonly caused disease is the Coxsackie A disease, presenting as hand, foot and mouth disease. It may be asymptomatic or cause mild symptoms, or it may produce fever and painful blisters in the mouth (herpangina), on the palms and fingers of the hand, or on the soles of the feet. There can also be blisters in the throat or above the tonsils. Adults can also be affected. The rash, which can appear several days after high temperature and painful sore throat, can be itchy and painful, especially on the hands/fingers and bottom of feet.

• Acne - typical of teenagers, usually appears on the face and upper neck, but the chest, back and shoulders may have acne as well. The upper arms can also have acne, but lesions found there are often keratosis pilaris, not acne. The typical acne lesions are comedones and inflammatory papules, pustules, and nodules. Some of the large nodules were previously called "cysts"

• Syphilis - commonly presents with gneralized systemic symptoms such as malaise, fatigue, headache and fever. Skin eruptions may be subtle and asymptomatic Classically described as 1) non-pruritic bilateral symmetrical mucocutaneous rash; 2) non-tender regional lymphadenopathy; 3) condylomata lata; and 4) patchy alopecia.

• Molluscum contagiosum - lesions are commonly flesh-colored, dome-shaped, and pearly in appearance. They are often 1-5 millimeters in diameter, with a dimpled center. Generally not painful, but they may itch or become irritated. Picking or scratching the lesions may lead to further infection or scarring. In about 10% of the cases, eczema develops around the lesions. They may occasionally be complicated by secondary bacterial infections.

• Mononucleosis - Common symptoms include low-grade fever without chills, sore throat, white patches on tonsils and back of the throat, muscle weakness and sometime extreme fatigue, tender lymphadenopathy, petechial hemorrhage and skin rash.

• Toxic erythema - common rash in infants, with clustered and vesicular appearance.

• Rat-bite fever - commonly presents with fever, chills, open sore at the site of the bite and rash, which may show red or purple plaques.

• Parvovirus B19 - the rash of fifth disease is typically described as "slapped cheeks," with erythema across the cheeks and sparing the nasolabial folds, forehead, and mouth.

• Cytomegalovirus - common symptoms include sore throat, swollen lymph nodes, fever, headache, fatigue, weakness, muscle pain and loss of appetite.

• Scarlet fever - commonly includes fever, punctate red macules on the hard and soft palate and uvula (Forchheimer's spots), bright red tongue with a "strawberry" appearance, sore throat and headache and lymphadenopathy.

• Rocky Mountain spotted fever - symptoms may include maculopapular rash, petechial rash, abdominal pain and joint pain.

• Stevens-Johnson syndrome - symptoms may include fever, sore throat and fatigue. Commonly presents ulcers and other lesions in the mucous membranes, almost always in the mouth and lips but also in the genital and anal regions. Those in the mouth are usually extremely painful and reduce the patient's ability to eat or drink. Conjunctivitis of the eyes occurs in about 30% of children. A rash of round lesions about an inch across, may arise on the face, trunk, arms and legs, and soles of the feet, but usually not on the scalp.

• Varicella-zoster virus - commonly starts as a painful rash on one side of the face or body. The rash forms blisters that typically scab over in 7-10 days and clears up within 2-4 weeks.

• Chickenpox - commonly starts with conjunctival and catarrhal symptoms and then characteristic spots appearing in two or three waves, mainly on the body and head, rather than the hands, becoming itchy raw pox (small open sores which heal mostly without scarring). Touching the fluid from a chickenpox blister can also spread the disease.

• Meningococcemia - commonly presents with rash, petechiae, headache, confusion, and stiff neck, high fever, mental status changes, nausea and vomiting.

• Rickettsialpox - first symptom is commonly a bump formed by a mite-bite, eventually resulting in a black, crusty scab. Many of the symptoms are flu-like including fever, chills, weakness and muscle pain but the most distinctive symptom is the rash that breaks out, spanning the person's entire body.

• Meningitis - commonly presents with headache, nuchal rigidity, fever, petechiae and altered mental status.

• Impetigo - commonly presents with pimple-like lesions surrounded by erythematous skin. Lesions are pustules, filled with pus, which then break down over 4-6 days and form a thick crust. It's often associated with insect bites, cuts, and other forms of trauma to the skin.

External links

• Association of Medical Microbiologists page on parvovirus B19
• Parvovirus B19 Information
• fifthdisease.org