The Epidemiological and Immunological Attributes for the Progress and Outcomes of Covid-19 Disease in Tanzania

COVID-19, a disease caused by a novel Severe Acute Respiratory Syndrome Coronavirus - 2 (SARS-CoV-2), was first identified in China and quickly spread at global level, including Tanzania [1]-[3]. SARS-CoV-2 is, together with SARS-CoV-1 (2002-2003) and the Middle East Respiratory Syndrome CoV (MERS-CoV,2012), one of three zoonotic betacoronaviruses known to have crossed the species barrier and caused outbreaks in humans [4]-[7]. More than 400,000 deaths and over 7,000,000 cases of SARS-CoV-2 have been reported globally as of 14th June 2020. Europe, Asia and North America remain the most severely affected countries with high COVID-19 fatality rates. Despite a huge volume of traffic between China where the first cases of COVID -19 were reported and Africa, there was a delay in conformation of a first case of the virus on the African continent. Contrary to the expectations of many, to date, Africa remains the least affected region globally, with 1·5% of the world's reported COVID-19 cases and 0·1% of the world's deaths [1], [8]. This phenomenon has been associated with several theories, including inability of African countries to conduct effective viral surveillance, sensitivity of the virus to warm weather conditions in most African countries and Africa's relatively young population. Other biological factors may potentially modulate Africans' immune responses to SARS-CoV-2, including host factors, such as genetic background, gender and age; and environmental dynamics such as prior exposure to similar pathogens and the nutritional status. Host genetic background, such as polymorphisms in HLA and Fc receptor genes influence the immunological outcome of infection or vaccination in specific study populations [9], [10]. Similarly, Lassaunière and Tiemessen reported that FcγR variant distribution and linkage disequilibrium differs in Africans and Caucasians in a manner that suggests a differentially maintained balance of FcγRmediated cell activation in these populations [13]. While HLA genes are critical in host immune responses to microbes, Fc receptors also mediate a various function including clearance of infected cells, activation of immune cells and regulation of antibodies and a range of cytokine production. SARS-CoV-2 exposed individuals elicit antibodies with varying binding and neutralizing capacity [14], it is therefore likely that the produced antibodies activate the Fc receptor pathways in containing the virus and that variations in Fc receptor genes affect the role of these receptors in the control of SARS-CoV-2 infection. Moreover, genes encoding for SARS-CoV-2's entry receptor to host cells, angiotensinconverting enzyme 2 (ACE-2) may also vary between populations, which may in turn affect populations' susceptibility to SARS-CoV-2. Since COVID-19 pandemic is projected to continue spreading, it is crucial to understand the risk factors for SARSCoV- 2 disease in Africa. Herein, we propose to explore the epidemiological and host immunological factors to acquiring SARS-CoV-2 and progressing to severe illness in Tanzania. We intend to describe characteristics that influence the outcome of COVID-19 in different demographic groups (age, sex, geographic location) and in people with different lifestyles, medical histories (eg: pre-existing conditions vs none). This information is required especially to resource-limited countries in order to: (1) give a scientific explanation on the difference in the dynamic of COVID-19 in different regions/countries and (2) identify populations at high risk for acquiring SARS-CoV-2 infection and progression to severe disease in order to help the government to make decisions on prioritizing limited-resources to those at highest risk of COVID-19. Expected Outputs The proposed study will interrogate differences in epidemiologic, immunologic and genetic profiles of people who recovered from COVID-19 of different severity. The project will further investigate whether SARS-CoV-2 unexposed individuals have immunity that can cross-react with SARS-CoV-2. Data generated from this project will shed light about populations that are at greater risk of progressing to severe forms of COVID-19. This information will help the responsible authorities and healthcare providers in mitigating the effects of COVID-19 by identifying and targeting interventions to priority populations. Further, findings from this study will provide baseline information for further research towards management and control of COVID-19.