Human Parainfluenza Virus 3 - Symptoms and illnesses
Parainfluenza virus type 3 is one of a group of common viruses known as human parainfluenza viruses (HPIV) that cause a variety of respiratory illnesses. Symptoms usually develop between 2 and 7 days from the time of exposure and typically resolve in 7-10 days. Symptoms may include fever, runny nose, and cough. HPIV-3 can also cause bronchiolitis, bronchitis, and pneumonia. Infants and young children are particularly susceptible to HPIV-3 infections, though older adults and those with a weakened immune system are also at risk for complications. HPIVs are usually spread from an infected person to others through coughing, sneezing, and/or touching. Most adults have antibodies against parainfluenza but can get repeat infections. The incubation period, the time from getting infected with HPIV to onset of symptoms, is generally 2 to 6 days. HPIV-1 and HPIV-2 are most often associated with croup, with HPIV-1 most often identified as the cause in children. Both can also cause upper and lower respiratory illness and cold-like symptoms. HPIV-3 is more often associated with bronchiolitis, bronchitis, and pneumonia. HPIV-4 is recognized less often but may cause mild to severe respiratory tract illnesses. Upper respiratory illness from any HPIV is generally common cold symptoms. Signs and symptoms may include:
Reinfections
People can get multiple HPIV infections in their lifetime. These reinfections usually cause mild upper respiratory tract illness with cold-like symptoms. However, reinfections can cause serious lower respiratory tract illness, such as pneumonia, bronchitis, and bronchiolitis in some people. Older adults and people with weakened immune systems have a higher risk for severe infections. Most children 5 years of age and older have antibodies against HPIV-3 and approximately 75% have antibodies against HPIV-1 and HPIV-2.
Transmission
HPIVs usually spread by direct contact with infectious droplets or by airborne spread when an infected person breathes, coughs, or sneezes. HPIVs may remain infectious in airborne droplets for over an hour and on surfaces for a few hours depending on environmental conditions. People are most contagious during the early stage of illness.
HPIV Seasons
There are four types of HPIVs and two subtypes that circulate at different times of the year. HPIV-1 infections often cause croup in children. There are usually more cases in the fall of every other year. HPIV-2 infections can also cause croup. HPIV-2 infections occur more commonly in the fall of every other year during the years when HPIV-1 is low. It is less frequently detected than HPIV-1 and HPIV-3. HPIV-3 infections usually occur in spring and early summer months each year. However, HPIV-3 infections can occur throughout the year, particularly when HPIV-1 and HPIV-2 are not in season. HPIV-4 (subtypes 4a and 4b) seasonal patterns are not as well characterized, but appear to occur in fall and winter each year.
Prevention and treatment
Currently, there is no vaccine to prevent HPIV infection. However, researchers are trying to develop vaccines. Also, there is no specific antiviral treatment for HPIV illness. Most HPIV illnesses are mild and typically require only treatment of symptoms. In hospital settings, healthcare providers should follow contact precautions, such as handwashing and wearing protective gowns and gloves. For more information, see CDC’s 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings.
Overview
HPIVs belong to the Paramyxoviridae family. They are enveloped RNA viruses. There are four types (1 through 4) and two subtypes (4a and 4b) of HPIVs. The clinical and epidemiological features for each HPIV type can sometimes vary. In the United States, infections associated with HPIV-1 usually peak every other year. Infections with HPIV-2 also peak every other year, during the years when HPIV-1 is low. HPIV-3 usually has peaks annually, particularly when HPIV-1 and HPIV-2 are low. Infections with HPIV-4 are less well-defined but appear to occur yearly. HPIVs commonly infect infants, young children, and persons with weakened immune systems. However, anyone can get HPIV infection.
