COVID-19 : EPIDEMIOLOGY, CLINICAL PRESENTATION AND PROGNOSIS Logan S. Ledet, MD, Fred A. Lopez, MD, MACP
Dr. Ledet is a Fellow in the Section of Infectious Diseases, Department of Internal Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA Dr. Lopez is the Richard Vial Professor and Vice Chair of Education in the Department of Internal Medicine, Louisiana State University Health Sciences Center, New w, LA, USA
ABSTRACT Since the first case of COVID-19 was reported inWuhan City, Hubei Province, China, in December 2019, an ensuing pandemic has challenged public health infrastructure around the world. During this time, scientists and clinicians have been striving to understand, prevent, and treat this disease, generating an enormously robust amount of data in the process. This article aims to provide clinicians with up-to-date, useful and accurate information regarding the virus’s origins, transmission dynamics, clinical presentation, and prognosis that can help inform their practice in this challenging, and constantly evolving health crisis.
HISTORY AND EPIDEMIOLOGY Throughout human history, society has been shaped by intermittent outbreaks of infectious diseases described as “plagues” and/or “pandemics.” Outbreaks of infectious diseases have changed the course of history, transforming economies and affecting the outcomes of wars, causing devastation but also leading to amazing advancements in public health and medicine. Since the beginning of the 21st century, some of the most notable outbreaks of infectious diseases have been due to novel viruses from the family Coronaviridae. The 2003 outbreak of Severe Acute Respiratory Syndrome (SARS) ultimately resulted in more than 8,000 cases with an approximate 10% mortality rate. The disease, first documented in Hong Kong, spread rapidly over multiple continents, sparking worldwide fear and causing disastrous economic impacts 1 . No cases have been reported since 2004. Again, in 2012, a SARS-like coronavirus illness emerged in Saudi Arabia. Deemed Middle East Respiratory Syndrome (MERS), this outbreak led to more than 1,000 cases with an even higher mortality rate estimated at almost 35% (2). In both instances, these viruses emerged in areas with dense human populations where there exist so-called “wet markets.” In these markets, fresh meat, fish, and produce are sold, allowing for frequent mixing of different animal species in close contact with human patrons. SARS-CoV and MERS-CoV originated from animal reservoirs. The SARS virus was originally traced to wildlife market civets, which likely acted as an amplifying intermediate animal host, and ultimately to bats. Likewise, MERS was traced to bats, with
dromedary camels acting as intermediate hosts. These viruses gained the ability to not only infect humans, but also achieve human-to-human transmission. The resulting illnesses included severe lower respiratory tract infections with extra-pulmonarymanifestations due to viruses abilities to infect a broad range of cell types while simultaneously evading host immune response and triggering cytokine dysregulation 1,2 . SARS-CoV and MERS-CoV served as harbingers of the pandemic we find ourselves in today, fully realized in COVID-19 caused by SARS-CoV-2. In December 2019, a cluster of severe pneumonia cases were described inWuhan City, Hubei Province, China. It was noted that a number of the patients affected had either visited or worked in the same local seafood market prior to becoming ill. Shortly thereafter, a novel coronavirus, now called SARS- CoV-2, was isolated via PCR from bronchoalveolar lavage fluid collected from infected patients 3 . Since isolation of the virus, much work has been done to determine its animal origins. Like SARS and MERS, this virus likely originated in bats. SARS-CoV-2 shares 96.2% sequence identity with a bat coronavirus, BatCoV RaTG13, first isolated from Rhinolophus affinis (intermediate horseshoe bat) in Yunnan province. Though a number of intermediate animal hosts have been proposed, including the pangolin, thus far the intermediate host or hosts have not been definitively identified. A WHO task force continues to investigate this issue 4 . SARS-CoV-2 spread rapidly thereafter, with the first case on US soil being reported on January 19, 2020, in Washington state 5 . Eleven days later, on January 30th, the WHO declared 5
Made with FlippingBook Digital Publishing Software