**5.4. Epstein-Barr virus**

**5.1. Adenoviruses**

196 Contemporary Topics of Pneumonia

**5.2. Coronavirus**

respiratory syndrome) [39].

**5.3. Cytomegalovirus**

the United States and in the Pacific Northwest [38].

household contacts and in healthcare settings [40].

Adenoviruses are enveloped DNA viruses and a diverse group that cause a wide spectrum of clinical illnesses. At least 52 serotypes exist, classified into 7 subgroups or species (A-G). Adenovirus pneumonia typically is limited to newborns, immunocompromised hosts, and school or military camp populations. Severe adenovirus pneumonia has been more commonly described in immunocompromised patients. Respiratory infection in immunocompetent patients is usually self-limited and mild [37]. However, with advances in molecular techniques, adenovirus has been increasingly discovered to be involved in sporadic cases and in severe CAP in healthy adults. Pulmonary disease is predominantly caused by serotypes 1, 2, 3, 4, 5, 7, 14, and 21. Adenovirus infection accounts for up to 20% of childhood pneumonias, primarily in those children younger than 5 years of age, but such pneumonias occur infrequently in the non-military adult population. Types 4 and 7 viruses can cause outbreaks of respiratory disease in military recruits, whereas Type 7 viruses can cause bronchiolitis and pneumonia in infants. A virulent strain of Adenovirus, serotype 14 (subgroup B) has been reported to cause greater symptoms of respiratory illness and pneumonia. It was first observed in 2005 among civilian and military populations. Outbreaks occurred subsequently at military academies throughout

Coronaviruses are from the family Coronaviridae and are single-stranded RNA viruses. As the name indicates the surface is covered by crown like projections. This virus is spread via droplet and fomite exposure. Coronaviruses were not thought to significantly cause pneumonia until recently. However, the severe acute respiratory syndrome (SARS) pandemic in 2003 brought

There are six human coronaviruses (HCoVs) that are established human pathogens with worldwide distribution, causing upper and lower respiratory tract infections: HCoV-229E, OC43, HKU1, NL63, MERS-COV (Middle East respiratory syndrome) and SARS-COV (severe acute

MERS-COV was first identified in Saudi Arabia in September 2012, approximately 2000 MERS-CoV cases have been detected in over 20 countries. The newly reported cases lift Saudi Arabia's MERS-CoV total since the virus was first detected in humans in 2012 to 1598 cases, 661 of them fatal and the majority of MERS-CoV cases continue to be reported from the Middle East. The source of the virus has remained a mystery but transmission and virological studies point toward dromedary camels in the Middle East by which humans may become infected through zoonotic transmission. Human-to-human transmission is then exacerbated through close

Cytomegalovirus (CMV) is a herpesvirus that is a common cause of infections. In hosts who are immunocompetent, acute CMV infection causes a mononucleosis-like syndrome. CMV

the ability of this virus to cause life-threatening pneumonia to worldwide attention.

Epstein-Barr virus (EBV) is well-known to be transmitted through infected saliva. The virus can cause pneumonia without mononucleosis. Lung involvement secondary to EBV infections usually only occurs in immunocompromised people. However, in 25% of pediatric patients with HIV infection, the virus can cause lesions due to lymphocytic interstitial pneumonia or pulmonary lymphoid hyperplasia.

Infectious mononucleosis occurs in young adults aged 15–30 years and usually resolves without *sequelae*. This disorder may cause chronic tiredness and fevers but can also be complicated by life-threatening problems. Pulmonary involvement associated with Epstein-Barr virus infection is uncommon but can occur as a complication of infectious mononucleosis. Pathologically, mononuclear inflammatory cells are evident along interlobular septa in interstitial pulmonary infiltrates [43].
