Clinical Significance

Respiratory viruses are responsible for a wide range of acute respiratory tract infections including the common cold, influenza, and croup and represent the most common cause of acute illness in the United States. Disease severity can be especially high in the young, the immunocompromised, and elderly patients. Accurate and timely diagnosis of the cause of respiratory tract infections has many benefits. They include improved treatment of the patient by ensuring appropriate antiviral treatment (e.g. oseltamivir for influenza), decreasing the overall cost of care, reducing selection for antimicrobial resistant organisms due to excessive and inappropriate use of antibiotics,1 assisting infection control personnel in providing appropriate measures to minimize nosocomial spread, and providing valued information to public health authorities regarding which viruses are circulating in the community.

Adenoviruses are members of the Adenoviridae family which commonly cause respiratory illness which can range from the common cold to pneumonia, croup, and bronchitis. Depending on the type, Adenoviruses can cause other illnesses such as gastroenteritis, conjunctivitis, cystitis, and, less commonly, neurological disease. Infants and people with weakened immune systems are at high risk for developing severe illness caused by Adenovirus infection.

Human Metapneumovirus (hMPV) is a common respiratory pathogen associated with both upper and lower respiratory tract infections and may be a trigger for asthma. Symptoms commonly associated with hMPV include cough, fever, nasal congestion, and shortness of breath. Clinical symptoms of hMPV infection may progress to bronchiolitis or pneumonia and are similar to other viruses that cause upper and lower respiratory infections. The incubation period is estimated to be 3 to 6 days, and the median duration of illness can vary depending upon severity but is similar to other respiratory infections caused by viruses.

Rhinoviruses, members of the family Picornaviridae, are the causative pathogens in more than half of viral respiratory infections, and they are associated with acute exacerbations of respiratory disease, including asthma, sinusitis, otitis media, and COPD. Studies have confirmed rhinoviruses as being the most common cause of “the common cold” and affect all age groups. Symptoms usually include sore throat, runny nose, coughing, sneezing, watery eyes, headaches and body aches. Most people recover within about 7-10 days.

Human parainfluenza viruses (HPIVs) belong to the Paramyxoviridae family. There are four types (1 through 4). The clinical and epidemiological features for each HPIV type can vary. HPIVs commonly infect infants and young children, however, anyone can get the HPIV infection. HPIV-1 and HPIV-2 both cause 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 not recognized as often but may cause mild to severe respiratory tract illnesses. The incubation period, the time from exposure to HPIV to onset of symptoms, is generally 2 to 7 days.