People with conditions that affect the immune system (immunodeficiency conditions) are at risk for developing acute or chronic anemia as a result of an infection with parvovirus B19.
Conditions in which an infection with this virus can cause chronic anemia include:
- Acute lymphocytic leukemia (ALL) or other cancers
- Certain congenital immunodeficiencies
- Organ transplant recipients.
Parvovirus B19 infections usually do not affect the fetus. It is estimated that less than 10 percent of infections in pregnant mothers cause fetal death. When fetal death does occur, it is most commonly due to nonimmune hydrops fetalis (excess fluid in the connective tissue of the fetus), which causes severe anemia and congestive heart failure.
There is no evidence that a parvovirus B19 infection in the mother can cause birth defects.
Parvovirus B19 has been found in the respiratory secretions (e.g., saliva, sputum, and nasal mucus) of infected people before the onset of the rash, when they appear to "just have a cold." The virus is probably spread from person to person by direct contact with those secretions, such as sharing drinking cups or utensils.
In a household, as many as 50 percent of susceptible people (those who are exposed to a family member who has parvovirus B19) may become infected. During school outbreaks of the virus, 10 to 60 percent of students may get fifth disease.