Those that cause pneumonia as a primary manifestation of disease include influenza virus types A and B, Respiratory synctytial virus (RSV), adenovirus, parainfluenza virus, rhinovirus, Hantavirus, and cytomegalovirus (CMV). Those that cause pneumonia as part of a multi-system syndrome include Paramyxovirus species (measles), varicella-zoster virus, Epstein-Barr virus, CMV, and herpes simplex virus (Hull, 1989).
Patients with the greatest risk for severe disease are the elderly, patients whose immune systems are compromised, due to HIV or organ transplants, and those with underlying chronic illnesses. Certain medications, such as steroids, can also increase susceptibility of acquiring pneumonia in a patient. Viruses are also the most frequent cause of pneumonia in children, especially those with heart defects. Some patients have few, if any, physical signs or symptoms other than mild fever, while other patients may have respiratory failure. Other symptoms that may be present upon onset of viral pneumonia are: cough, headache, muscular stiffness and aching, shortness of breath, chills, sweating, fatigue, and sore throat. Conjunctivitis may also be a sign of viral pneumonia, although this symptom usually occurs when adenovirus is the culprit.
Over the past decade, developments in diagnostic techniques have led to a significant improvement in the ability to detect viruses in the respiratory tract. However, the detection of viral pathogens does not always indicate active disease. For example, herpes viruses may become reactivated without causing significant active disease. Similarly, RSV and CMV can be detected in the presence of other known bacterial pathogens, making it difficult to decide whether these are the causative agents of pneumonia (Hull, 1989). For an accurate diagnosis, temperature, heart rate, and blood pressure are usually checked. A small clamp, which looks like a clothespin, can be put on the finger to check blood oxygen level.