Leadership and early strategic response to the SARS-CoV-2 pandemic at a COVID-19 designated hospital in South Africa

While many countries are preparing to face the COVID-19 pandemic, the reported cases in Africa remain low. With a high burden of both communicable and non-communicable disease and a resource-constrained public healthcare system, sub-Saharan Africa is preparing for the coming crisis as best it can. We describe our early response as a designated COVID-19 provincial hospital in Cape Town, South Africa (SA).While the first cases reported were related to international travel, at the time of writing there was evidence of early community spread. The SAgovernment announced a countrywide lockdown from midnight 26 March 2020 to midnight 30 April 2020 to stem the pandemic and save lives. However, many questions remain on how the COVID-19 threat will unfold in SA, given the significant informal sector overcrowding and poverty in our communities. There is no doubt that leadership and teamwork at all levels is critical in influencing outcomes

High HIV prevalence in an early cohort of hospital admissions with COVID-19 in Cape Town, South Africa

Background. South Africa (SA) has a high prevalence of HIV and tuberculosis. Cape Town was the SA metropole most affected in the early stages of the COVID-19 pandemic. Early observational data from Africa may provide valuable insight into what can be expected as the pandemic expands across the continent.Objectives. To describe the prevalence, clinical features, comorbidities and outcome of an early cohort of HIV-positive and HIV-negative patients admitted with COVID-19.Methods. This was a descriptive observational study of an early cohort of adults with COVID-19 pneumonia admitted from 25 March to 11 May 2020.Results. Of 116 patients (mean age 48 years, 61% female) admitted, 24 were HIV-positive (21%). The most common symptoms reported were cough (n=88; 73%), shortness of breath (n=78; 69%), fever (n=67; 59%), myalgia (n=29; 25%) and chest pain (n=22; 20%). The most common comorbidities were hypertension (n=46; 41%), diabetes mellitus (n=43; 38%), obesity (n=32; 28%) and HIV (n=24; 21%). Mortality was associated with older age (mean (standard deviation) 55 (12) years v. 46 (14) years; p<0.01); the presence of hypertension or hypertension along with diabetes and/or obesity; lower partial pressure of arterial oxygen to fraction of inspired oxygen ratio; and higher urea level, white cell count, neutrophil count, and C-reactive protein, lactate dehydrogenase and ferritin levels, and high neutrophil to lymphocyte ratio. The overall survival rate for all hospital admissions was 86/116 (73%). In this early cohort, survival was similar in patients with HIV (n=18; 75%) compared with those without HIV (n=67; 75%) (p=1). Of the 74 patients admitted to the wards, 63 (85%) survived, whereas 22 of 42 (52%) admitted to the intensive care unit survived.Conclusions. Patients with HIV infection represented a large proportion of all COVID-19 admissions. The presentation and outcome of patients with HIV did not differ significantly from those of patients without HIV

Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow

We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process

Unresolved Gamma-Ray Sky through its Angular Power Spectrum

The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi -large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission [unresolved gamma-ray background (UGRB)] below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This Letter presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi-LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55±0.23 and 1.86±0.15

High-energy emission from a magnetar giant flare in the Sculptor galaxy

Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 1013–1015 G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft γ rays1,2. Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. 3,4 and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV γ rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these γ rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological γ-ray burst. Thus, we infer that the γ rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV γ rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short γ-ray bursts

Investigating the Nature of Late-time High-energy GRB Emission through Joint Fermi/Swift Observations

Abstract We use joint observations by the Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveals that LAT nondetections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the nondetected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1\u2013100 GeV energy range considered for this analysis

High HIV prevalence in an early cohort of hospital admissions with COVID-19 in Cape Town, South Africa

CITATION: Parker, A. et al. 2020. High HIV prevalence in an early cohort of hospital admissions with COVID-19 in Cape Town, South Africa. South African Medical Journal, doi:10.7196/SAMJ.2020.v110i10.15067.The original publication is available at http://www.samj.org.zaBackground. South Africa (SA) has a high prevalence of HIV and tuberculosis. Cape Town was the SA metropole most affected in the early stages of the COVID-19 pandemic. Early observational data from Africa may provide valuable insight into what can be expected as the pandemic expands across the continent. Objectives. To describe the prevalence, clinical features, comorbidities and outcome of an early cohort of HIV-positive and HIV-negative patients admitted with COVID-19. Methods. This was a descriptive observational study of an early cohort of adults with COVID-19 pneumonia admitted from 25 March to 11 May 2020. Results. Of 116 patients (mean age 48 years, 61% female) admitted, 24 were HIV-positive (21%). The most common symptoms reported were cough (n=88; 73%), shortness of breath (n=78; 69%), fever (n=67; 59%), myalgia (n=29; 25%) and chest pain (n=22; 20%). The most common comorbidities were hypertension (n=46; 41%), diabetes mellitus (n=43; 38%), obesity (n=32; 28%) and HIV (n=24; 21%). Mortality was associated with older age (mean (standard deviation) 55 (12) years v. 46 (14) years; p<0.01); the presence of hypertension or hypertension along with diabetes and/or obesity; lower partial pressure of arterial oxygen to fraction of inspired oxygen ratio; and higher urea level, white cell count, neutrophil count, and C-reactive protein, lactate dehydrogenase and ferritin levels, and high neutrophil to lymphocyte ratio. The overall survival rate for all hospital admissions was 86/116 (73%). In this early cohort, survival was similar in patients with HIV (n=18; 75%) compared with those without HIV (n=67; 75%) (p=1). Of the 74 patients admitted to the wards, 63 (85%) survived, whereas 22 of 42 (52%) admitted to the intensive care unit survived. Conclusions. Patients with HIV infection represented a large proportion of all COVID-19 admissions. The presentation and outcome of patients with HIV did not differ significantly from those of patients without HIV.http://www.samj.org.za/index.php/samj/article/view/13054Publisher's versio

Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with $kT_{\rm in} \approx$ 1 keV, plus unsaturated Comptonization in thermal plasma with temperature $kT_{\rm e} = 3$ keV and optical depth $\tau \approx 4$, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band $P=1.8 \pm 0.3$ per cent and polarization angle $\phi = 140^{\circ} \pm 4^{\circ}$, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree $P =4.0 \pm 0.7$ per cent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.Comment: 10 pages, 7 figures, accepted for publication in MNRA