**1. Introduction**

Pneumonia was once known as Winter Fever and is an acute infection and inflammation of the lung parenchyma. It was first described by Hippocrates around 460 BC [1] . However, it wasn't until the 19th century that pneumonia was established as a true infection, and not just a symptom of other diseases. Edwin Klebs a German pathologist in 1875 observed bacteria under a microscope in cases of pneumonia [2]. Then, Carl Friedlander and Albert Frankel in

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

1884 and 1884 respectively identified two of the most common bacterial causes of pneumonia, *Streptococcus pneumoniae* and *Klebsiella pneumonia* [3]. By the 1930s, treatment for pneumonia had been developed with the introduction of penicillin playing a key role.

Respiratory viruses such as RSV or rhinovirus that damage the respiratory tract cause release of multiple humoral factors, including leukotriene C4, and histamine. In the case of RSV virusspecific immunoglobulin E is released. Rhinovirus infections can cause release of bradykinin, interleukin 1, interleukin 6, and interleukin 8. A further complication of RSV infections is that they can increase bacterial adherence to respiratory epithelium, impair mucociliary clearance,

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In co infections, secondary bacterial superinfection makes for a poor prognosis of the original viral infection [13]. Interleukin-10, is purported to attract large numbers of macrophages and neutrophils to the lung. The presence of these cytokines increases the immune response, caus-

Numerous studies by the WHO have estimated there are over 450 million cases of pneumonia globally with approximately 3 million deaths particularly prone are the elderly and children [14]. The annual rate of CAP increases from 6/1000 in the 18–39 age group to 34/1000 in 75 years and over age group. Incident rates tend to be higher in colder climates of the North and hospitalization is required in 20–40% cases. In severe cases mortality can vary from 5 to

Viral pneumonias are common in the Mideast. In an Iranian study viruses causing pneumonia were Influenza A (7.4%), influenza B (3.5%), RSV (12.9%), and adenovirus (5.9%). Parainfluenza-1,2 and 3 were 6.4, 6.4 and 15.8% respectively [16]. More recently, avian influenza has become endemic in some parts of the Middle East, especially Egypt and

WHO data published in May 2014 Influenza and Pneumonia Deaths in Saudi Arabia reached 5689 or 7.08% of total deaths. The age adjusted death rate is 44.89 per 100,000 of population [18]. Middle East respiratory syndrome is caused by a novel coronavirus (MERS-CoV) first isolated in the Kingdom of Saudi Arabia in 2012 from the respiratory tract secretions of a Saudi businessman who died from viral pneumonia [19]. Subsequently, cases were identified in patients living outside the Arabian Peninsula and the Middle East, who were infected either during a stay in the Middle East or by close contact with an individual from an endemic country. Most affected patients were previously healthy men with a median age of 50 years [20]. In 2016, the World Health Organization (WHO) published a report on 1698 laboratoryconfirmed cases of MERS-CoV infection. The mortality rate was 36%. All cases were directly or indirectly linked through residence or travel to Saudi Arabia, the UAE, Jordan, Qatar, Oman, Lebanon, Kuwait, Yemen, Egypt, and Iran. There were also reports of sporadic reports in other countries including the United Kingdom, France, Malaysia, Tunisia, Italy, Austria, Greece, Turkey, the United States of America, Germany, Philippines, and Thailand [21]. The largest outbreak of the virus outside its endemic region was recorded in 2015, in South Korea. One-hundred and eighty-six additional cases were confirmed, including the first in China, with a total of 36 deaths. MERS-CoV is a zoonotic virus that can lead to secondary human

and cause changes in bacterial phagocytosis by host cells [12].

**3. Epidemiology**

10% of cases [15] .

Turkey [17].

ing inflammatory damage and preventing the proper removal of bacteria.

Pneumonia remains the leading cause of childhood mortality under the age of 5 and the most common reason for adult hospitalisation in low and middle income countries, despite advances in preventative and management strategies [4]. Pneumonia usually causes symptoms for 3–4 weeks, and daily activities may be impaired for a further 3 weeks on average. Community-acquired pneumonia (CAP) refers to pneumonia acquired outside of hospitals or extended-care facilities. Nosocomial pneumonia and hospital-acquired pneumonia describe infections acquired in the hospital setting. These are usually defined as pneumonia that occurs 48 h or more after hospital admission, and which was not incubating at the time of admission. Community-acquired pneumonia continues to be a significant health issue [5]. Annually in the United States there are around 4 million cases of which 20% of cases may require hospitalization. As a result there are more than 65 million days of reduced activity overall. Mortality rates can range from 1 to 30% making it the sixth leading cause of death [6]. In developing countries pneumonia is either the first or second leading cause of death. In Europe, around 14.4 per 10,000 children aged over 5 years and 33.8 per 10,000 under 5 years are diagnosed with CAP. CAP is more common in the developing world, estimated at 0.28 episodes per child per year and accounting for 95% of all cases [7].
