Coronavirus disease 2019 (COVID-19) has spread rapidly and extensively to most countries in the world, resulting in considerable mortality in Europe and the United States, as well as in numerous upper-middle-income countries in South America and Asia. Experts predicted millions of COVID-19 deaths in Africa because many countries in the continent rank poorly on the United Nations Development Programme's Human Development Index. However, more than 4 months after the first cases in Africa were detected, prevalence and mortality are still low. It remains unclear if Africa is really spared from substantial cases and deaths. However, differences between Africa and the most affected countries in reliable reporting and death registration, lockdown stringency, demography, sociocultural aspects, environmental exposures, genetics, and the immune system could help to explain the experience of COVID-19 in Africa.
Africa faces major health and socioeconomic challenges that should have allowed rapid transmission of COVID-19. These include a weak health system (per capita health expenditure of <$50 in most West African countries compared with >$2500 in Europe and the United States), population crowding, poverty, and unhygienic conditions (1). Population densities are very high in most African capital cities such as Dakar (12,617 persons/km2), Abidjan (11,155 persons/km2), or Lagos (13,909 persons/km2), whereas New York City has 7101 persons/km2. However, although community transmission was reported in many major African cities months ago, the predicted number of cases and deaths has not yet been observed (see the figure). Low case numbers are often attributed to insufficient testing. However, many African countries implemented testing early on, and, based on the Our World in Data database (2), more tests per the number of cases were carried out than in other countries at similar phases of the epidemic (see the figure). Regarding the number of deaths, few functional civil registration services and thus statistics exist on the continent, raising questions about the reliability of mortality data. Potential underreporting of COVID-19associated deaths would not be specific to Africa, but the margin of error could be wider. To date, African countries have not indicated acute health emergencies; however, reliable age-stratified data are needed to fully grasp the COVID-19 situation in Africa to allow appropriate measures to be taken.
Measures such as travel restrictions, curfews, and school closures were implemented early in Africa compared with other continents, often before an African country had detected a case (fig. S1). These early responses might have resulted in fewer imported cases and reduced intracountry transmission, allowing sufficient time to prepare the constrained health systems for diagnosis and to prepare strategies for quarantine, contact tracing, and social distancing on a continent that already has experience in such practices to control epidemics such as Lassa fever and Ebola. Although it is likely that the early lockdown in Africa contributed to the slow spread, containment measures are not fully respected in many countries. Most people work in the informal business sector, such as in traditional markets, making strict lockdown measures impossible to implement. Recently, some African governments have been pressured to relax lockdown measures, for example, to carry out congregational prayers in mosques in Senegal. It remains unknown whether relaxation of containment measures will result in increased cases or if other factors are at play.
The majority of COVID-19associated deaths occur in older people. Africa has a comparatively young population, with a median population age of 19.7 years for the continent versus 38.6 years for the United States. Africa's youthful population is reflected in the structure of age-stratified cases (fig. S2). Based on global age-specific case fatality rates for COVID-19 and the age demographics of Africa, COVID-19 deaths would be expected to be only four times (3), rather than the observed 40 times, lower than in Europe or the United States. However, no aggregated data on age-specific case or death rates are available for the continent. There is substantial intergenerational mixing in Africa, and, with more cases of subclinical infections in the young, it could be a matter of time before expansive numbers of cases and deaths are recorded. Alternatively, a more rapid development of herd immunity among the youthful population might lead to fewer severe cases. Data from antibody tests (serosurveys) should clarify if transmission was more widespread with a high rate of asymptomatic and mild cases in African countries than in other countries.
The genetic characteristics of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and human genetics may be among the reasons for low incidence of severe COVID-19 in Africa. Although the relative contribution from Africa to the SARS-CoV-2 GISAID (Global Initiative on Sharing All Influenza Data) sequence database is small, the isolates found in Africa are representative of the different clades of SARS-CoV-2 found on other continents (fig. S3). Thus, it is unlikely that strains of SARS-CoV-2 in Africa have reduced virulence. Moreover, African-Americans constitute a disproportionate burden of deaths in the United States, so it seems unlikely that the lower mortality from COVID-19 in Africa is due to genetic factors. Nonetheless, the COVID Human Genetic Effort consortium aims to elucidate whether genetics can play a role in the patterns of disease worldwide.
SARS-CoV-2 infection leads to a heterogeneous outcome. About 80% of symptomatic cases are mild to moderate, whereas 20% can develop severe respiratory disease and display high rates of mortality (4). The development of an effective adaptive immune response can limit viral infection, whereas uncontrolled activation of innate immune cells leads to a cytokine storm and hyperinflammation in the lungs, ultimately leading to acute respiratory distress syndrome (ARDS) and multiorgan failure (4, 5). Being able to suppress viral infection early or to temper excessive inflammatory responses are likely complementary mechanisms to prevent severe disease.
Most convalescent symptomatic COVID-19 patients develop virus-specific neutralizing antibodies as well as specific CD4+ and CD8+ T cell responses (5). The efficiency and adequacy of these adaptive responses to clear viral infections depends on multiple factors, including past or concurrent infections with other pathogens. For example, antibodies directed to the four human coronaviruses that cause common colds could cross-react and neutralize SARS-CoV-2 in humans (6), and preexisting cross-reactive T cells can be found in individuals that have not been exposed to SARS-CoV-2 (7), suggesting previous exposure to related human coronaviruses could generate immunological cross-reactivity (7).
There are considerable differences in environmental exposures in Africa, compared with Europe or the United States. Noncommunicable diseases (NCDs)such as cardiovascular diseases, obesity, and type 2 diabetesare risk factors for severe COVID-19. These environmentally and behaviorally driven conditions are increasingly recognized in urban centers in Africa, and most COVID-19 deaths in Africa have been in older people with NCDs. However, infectious diseases such as HIV, tuberculosis, malaria, and other respiratory infections or those caused by helminths (parasitic worms) are prevalent in Africa, but there is currently little information on whether, or how, these infections affect COVID-19 disease progression.
The distribution of coronavirus disease 2019 (COVID-19) cases and deaths per 1 million inhabitants per continent reveals surprisingly low rates in Africa (left). This is despite comparable levels of testing per confirmed cases across continents (right). The dotted lines show the number of tests performed per number of detected cases. Data are from European Centre for Disease Prevention and Control COVID-19 situation updates, United Nations World Population Prospects 2019, and Our World in Data (2).
It is increasingly recognized that the immune system is shaped not only by genetics but also by environmental factors, such as exposure to microorganisms and parasites. This educates the immune system to protect against invading pathogens not only specifically but also nonspecifically through, for example, trained immunity, which involves the reprogramming of innate cells that, on secondary encounter with a pathogen, can show a stronger response (8) or virtual memory (9). Virtual memory T cells (TVM cells) expand in response to cytokines such as helminth-induced interleukin-4 (IL-4), rather than through pathogen-specific antigens, leading to enhanced antiviral effector functions (9). Thus, it can be envisaged that TVM cells are more prevalent in people in Africa owing to the higher exposure to such pathogens. This could contribute to the control of SARS-CoV-2. Additionally, as postulated by the hygiene hypothesis, early and chronic exposure to pathogens leading to relentless immune cell activation in harsh environments induces a strong regulatory immune response to counteract excessive inflammation (10).
The ability to prevent excessive inflammation could be a critical parameter that is associated with COVID-19 outcome. Recent data suggest that inflammatory alveolar macrophages (AMs), which can arise from differentiation of recruited monocytes upon infection, are increased in the lungs of patients with severe COVID-19 (11). It is unclear whether these monocyte-derived AMs are an important source of the cytokine-release syndrome observed during SARS-CoV-2 infection or whether they are involved in the pathogenesis of ARDS. However, monocyte and macrophage inflammatory cytokines, such as IL-6, have been repeatedly observed to be a marker of severe COVID-19, and myeloid cells are thus likely to be associated with the hyperinflammation. Monocytes from African individuals with high exposure to pathogens can be less proinflammatory (12). Thus, their recruitment into the lungs might prevent high cytokine production and therefore lead to better outcomes of COVID-19. Moreover, the airway microbiota, as well as more distal gut microbiota, could play important roles in preventing or potentiating respiratory tract infections and modulating virus-induced inflammation, as has been shown for several respiratory viruses (13). The known variations in microbiota across geographical areas could thus also participate in modulating disease severity and should be studied.
Africa should be part of the roadmap for COVID-19 research. Although there are no available data on the immune responses in African COVID-19 patients, studies show clear differences in the activation, proinflammatory, and memory profiles of the immune cells not only in Africans versus Europeans but also among Africans with high and low exposure to microorganisms and parasites (14) (fig. S4). Does the difference in immunological profiles matter for the outcome of COVID-19 in Africa? This needs further investigation, and the pattern of COVID-19 in urban and rural Africa could be informative.
There are differences in opinion about whether the pattern of SARS-CoV-2 spread is different in Africa compared with that in the United States and Europe. So far, despite a paucity of data, it appears that the virus is spreading differently and potentially with an attenuated outcome in Africa. There has been limited testing of asymptomatic cases or of antibody titers. Therefore, it is unknown whether early interventions were successful in preventing transmission or whether there are differences in susceptibility between populations of different regions. Perhaps the COVID-19 pandemic can emphasize the need for widespread implementation of public health tools, such as high-quality data, accurate diagnostics for track and trace, good communication, and an effective vaccine. Early testing of vaccines in different regions of Africa is essential because the high degree of exposure to pathogens can limit some vaccine responses (15). The first COVID-19 vaccine testing is starting in South Africa (Ox1Cov-19 Vaccine VIDA-Trial), and others are planned. Hopefully, this will stimulate the full participation of Africa in research into the critical factors that hold the key to innovative solutions in the fight against the pandemic.
Continue reading here:
- Study Identifies Breast Cancer Risk and Disease-Causing Mutations in Women Over 65 - Cancer Network - November 28th, 2020
- Scientists say West Africans originally migrated to East Africa - Quartz Africa - November 28th, 2020
- Major new study unveils complexity and vast diversity of Africa's genetic variation - The Conversation CA - November 28th, 2020
- Future Visioning the Role of CRISPR Gene Editing: Navigating Law and Ethics to Regenerate Health and Cure Disease - IPWatchdog.com - November 28th, 2020
- Future Visioning The Role Of CRISPR Gene Editing: Navigating Law And Ethics To Regenerate Health And Cure Disease - Technology - United States -... - November 28th, 2020
- Understanding the immunology of COVID-19 - SelectScience - November 28th, 2020
- Scientists successfully implanted human genes into monkeys to increase their brain mass - Boing Boing - November 28th, 2020
- Thirteen TUM researchers among the most cited worldwide - India Education Diary - November 28th, 2020
- Twist Bioscience Reports Fourth Quarter and Full Year Fiscal 2020 Financial Results - Business Wire - November 28th, 2020
- Spaceflight does some weird things to astronauts bodies - MIT Technology Review - November 28th, 2020
- Amgen To Present At The Evercore ISI Virtual HealthCONx Conference - GuruFocus.com - November 28th, 2020
- How to use precision medicine to personalize COVID-19 treatment according to the patients genes - TheStreet - September 2nd, 2020
- Meiotic chromosome synapsis depends on multivalent SYCE1-SIX6OS1 interactions that are disrupted in cases of human infertility - Science Advances - September 2nd, 2020
- Thought to Be Extinct, New Guinea's Singing Dogs Found Alive in the Wild - Smithsonian Magazine - September 2nd, 2020
- Humans have had mystery DNA for 300,000 yearsand now we might finally know what it is - SYFY WIRE - August 10th, 2020
- The Secret to a Long, Healthy Life Is in the Genes of the Oldest Humans Alive - Singularity Hub - August 10th, 2020
- LogicBio Therapeutics Reports Second Quarter 2020 Financial Results and Provides Business UpdatesFDA Clears IND Application for LB-001 for the... - August 10th, 2020
- Research on Tasmanian devil offers new insights into tackling human cancer - National Science Foundation - August 10th, 2020
- Human Genetics Market 2020 Size by Product Analysis, Application, End-Users, Regional Outlook, Competitive Strategies and Forecast to 2027 - Owned - August 10th, 2020
- University of Texas researchers find mutation that led to 2015-2016 Zika outbreak - Homeland Preparedness News - August 10th, 2020
- Blood lipid levels may be altered in some autistic people - Spectrum - August 10th, 2020
- NIH taps Dr. Lindsey Criswell as director of the National Institute of Arthritis and Musculoskeletal and Skin Diseases - National Institutes of Health - August 10th, 2020
- 'Hyper urban' coyote genomes are growing apart from their city and rural cousins - Massive Science - August 10th, 2020
- Why scientists are worried about a 'Warp Speed' COVID-19 vaccine - New Haven Register - August 10th, 2020
- Gyroscope Announces Appointment of Leaders in Retinal Disease, Gene Therapy and the Complement System to Its Clinical and Scientific Advisory Boards -... - August 10th, 2020
- Noel Rose, Who Demonstrated Autoimmunity Exists, Dies at 92 - The Scientist - August 10th, 2020
- Invasion of the Body Snatchers: Viruses Can Steal Our Genetic Code to Create New Human-Virus Genes - SciTechDaily - August 10th, 2020
- Why Are Only 10% of People Left-Handed? Here's What Scientists Know So Far - ScienceAlert - August 10th, 2020
- Holder pasteurization of donated human milk is effective in inactivating SARS-CoV-2 - CMAJ - August 10th, 2020
- Dinosaur diagnosed with bone cancer that afflicts humans today - CNN - August 10th, 2020
- LogicBio Therapeutics Reports Second Quarter 2020 Financial Results and Provides Business Updates - GlobeNewswire - August 10th, 2020
- The Secret to Healthy Longevity Is in the Genes of the Oldest Humans Alive - Singularity Hub - August 10th, 2020
- BU's COVID-19 Testing Passes Its First Test | BU Today - BU Today - August 10th, 2020
- Pacific Biosciences and Asuragen Collaborate to Develop Assays for Carrier Screening and other Applications Based on SMRT Sequencing Technology and... - August 10th, 2020
- U of T researchers identify molecular switch allowing parasites to survive inside hosts without oxygen - News@UofT - August 9th, 2020
- LUMINEX : MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS (form 10-Q) - marketscreener.com - August 8th, 2020
- Gaucher Disease Treatment Market Size, Top Companies, Trends, Growth Factors Details by Regions, Types and Applications - Owned - August 8th, 2020
- How studying genetics and lifestyle can shape a healthier MENA region - The European Sting - August 8th, 2020
- Detection of H1 Swine Influenza A Virus Antibodies in Human Serum Samples by Age Group - CDC - August 7th, 2020
- UW researchers devise approach to treat rare, incurable form of blindness - University of Wisconsin-Madison - August 7th, 2020
- Prevail Therapeutics to Present at 2020 Wedbush PacGrow Healthcare Conference - Stockhouse - August 7th, 2020
- human genetics | Description, Chromosomes, & Inheritance ... - August 6th, 2020
- Human Genetics | Pitt Public Health | University of Pittsburgh - August 6th, 2020
- Triplet Therapeutics To Present at Upcoming Events - Business Wire - August 5th, 2020
- 'Hyper urban' coyote genomes are growing apart their from city and rural cousins - Massive Science - August 5th, 2020
- Baylor genomics teams partner to provide COVID-19 testing for Houston area - Baylor College of Medicine News - August 5th, 2020
- Gaucher Disease Treatment Market (Impact of COVID-19) Top Growing Companies: Acetelion Pharmaceutical (J&J Ltd.), Erad Therapeutic Inc., JCR... - August 5th, 2020
- High-fat Diet and Genetics Lead to Anxiety and Depression in Rats - Newswise - August 5th, 2020
- 'Mono' virus turns on cancer-related genes. Here's how. - Live Science - August 4th, 2020
- Human Challenge Trial Neither Essential Nor Ethically Justified at This Time, Says US Expert Anthony Fauci - Yahoo India News - August 4th, 2020
- ICMR to host global web conference on science, ethics of COVID-19 vaccine starting 4.30 pm today - Firstpost - August 4th, 2020
- Faculty/staff honors: Women in engineering network nod, winning magazine article on geologic hazards and refugees and two national genetics society... - July 31st, 2020
- ENCODE3: Interpreting the human and mouse genomes - Science Codex - July 31st, 2020
- Revealing the intrinsic functioning of human and mouse genomes - Tech Explorist - July 31st, 2020
- Maternal Immune Activation Causes Schizophrenia-like Behaviors in the Offspring through Activation of Immune-Inflammatory, Oxidative and Apoptotic... - July 31st, 2020
- Podcast: The ancient war between genes and disease - Genetic Literacy Project - July 31st, 2020
- Pitt's School of Public Health welcomes students with opera about obstetrician who championed hand-washing - TribLIVE - July 31st, 2020
- BNGO Stock Price: BioNano Genomics Inc. retreats, starts week in the red - FXStreet - July 31st, 2020
- A Genetic Mutation Reveals How the SARS-CoV-2 Virus Strikes - Technology Networks - July 31st, 2020
- 88-Year Old Daniel Smith, Son Of Slave, Tells His Story - Moguldom - July 31st, 2020
- 23andMe Releases Devastating Analysis of Trans-Atlantic Slave Trade - Futurism - July 31st, 2020
- MSU researcher earns grant to study effects of droughts - MSUToday - July 31st, 2020
- Massive Growth in Human Genetics Market Breaking new grounds and touch new level in Upcoming Year by QIAGEN, Agilent Technologies, Thermo Fisher... - July 30th, 2020
- CEO of genome analysis firm: We have the data to prove people will take care of themselves - University of Miami - July 30th, 2020
- Researchers from U of T, Harvard study collective human behaviour amid COVID-19 - News@UofT - July 30th, 2020
- Gene mutations discovered as a trigger for male infertility - BioNews - July 29th, 2020
- Cerevel Therapeutics and Cyclica Announce Research Collaboration to Use Artificial Intelligence to Accelerate Discovery of Novel Medicines in... - July 29th, 2020
- Relatives of coronavirus may have been in bats for decades - Opelika Auburn News - July 29th, 2020
- Link between platelets and Covid-19 virus? - The New Indian Express - July 29th, 2020
- Fortress Biotech Announces Publication of Study on Targeted Next Generation Sequencing for Newborn Screening of Menkes Disease in Molecular Genetics... - July 29th, 2020
- New 23andMe Study Reveals the Genetic Legacy of Slavery in the Americas - Gizmodo - July 29th, 2020
- The Groundbreaking Scientist Who Risked All in Pursuit of His Beliefs - The New York Times - July 29th, 2020
- 23andMe and GSK Head to Clinical Trials With Cancer Drug - MSN Money - July 29th, 2020
- Human Genetics - David Geffen School of Medicine at UCLA - July 29th, 2020
- Discovering how genetic 'dark matter' plays a role in mental illness is just the tip of the iceberg for human health - The Conversation UK - July 29th, 2020
- Prevail Therapeutics Granted Composition of Matter Patent for Experimental Gene Therapy Program PR006 - GlobeNewswire - July 29th, 2020
- The toll of shrinking jaws on human health | Stanford News - Stanford University News - July 28th, 2020
- Global Hereditary Genetic Testing Market (2020 to 2030) - Analysis and Forecast - GlobeNewswire - July 28th, 2020
- Triplet Therapeutics nabs Scholar Rock R&D exec as new CSO - FierceBiotech - July 27th, 2020
- Meet Dr Sarah Gilbert, one of the scientists leading the race to find a coronavirus vaccine - The Indian Express - July 27th, 2020