Are two consecutive negative RT-PCR results enough to rule out COVID-19?

The coronavirus disease 2019 (COVID-19) pandemic is redefining the world we live in, and scientists are struggling to find the best severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic tool. Routine testing is currently performed using real-time reverse transcription PCR (RT-PCR) of upper or lower respiratory tract secretions. We sought to demonstrate the importance of conducting RT-PCR using deep sampling when initial upper respiratory testing is negative in cases of high index of suspicion for COVID-19. We present the case of a 47-year-old man admitted for fever and bilateral pneumonia diagnosed via chest computed tomographic scan amidst the early peak of the COVID-19 pandemic, suggesting a SARS-CoV-2 infection. Two RT-PCR results from nasopharyngeal swab samples were negative. A bronchoscopy was then performed, and RT-PCR testing on bronchoalveolar lavage samples yielded positive results, confirming the diagnosis of COVID-19 pneumonia. RT-PCR samples of the lower respiratory tract likely contain a higher virus load and thus retain a higher sensitivity for SARS-CoV-2 detection.

Revisiting The Spectral and Timing Properties of NGC 4151.

NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole scale. Here, we report the results of a large XMM-Newton campaign in 2015 to study these short delays further. Analyzing high quality data that span time scales between hours and decades, we find that neutral and ionized absorption contribute significantly to the spectral shape. Accounting for their effects, we find no evidence for a relativistic reflection component, contrary to early work. Energy-dependent lags are significantly measured in the new data, but with an energy profile that does not resemble a broad iron line, in contrast to the old data. The complex lag-energy spectra, along with the lack of strong evidence for a relativistic spectral component, suggest that the energy-dependent lags are produced by absorption effects. The long term spectral variations provide new details on the variability of the narrow Fe Kα line. We find that its variations are correlated with, and delayed with respect to, the primary X-ray continuum. We measure a delay of τ = 3.3 - 0.7 + 1.8 days, implying an origin in the inner broad line region (BLR). The delay is half the Hß line delay, suggesting a geometry that differs slightly from the optical BLR.

[Analysis of the quality of data issued from Beirut's hospitals in order to measure short-term health effects of air pollution]. / Analyse de la qualité des données issues des hôpitaux de Beyrouth Municipe pour mesurer les effets à court terme de la pollution atmosphérique.

BACKGROUND: The effects of air pollution on human health have been the subject of much public health research. Several techniques and methods of analysis have been developed. Thus, Beirut Air Pollution and Health Effects (BAPHE) was designed to develop a methodology adapted to the context of the city of Beirut in order to quantify the short-term health effects of air pollution. METHODS: The quality of data collected from emergency units was analyzed in order to properly estimate hospitalizations via these units. This study examined the process of selecting and validating health and pollution indicators. RESULTS: The different sources of data from emergency units were not correlated. BAPHE was therefore reoriented towards collecting health data from the emergency registry of each hospital. A pilot study determined the appropriate health indicators for BAPHE and created a classification methodology for data collection. CONCLUSION: In Lebanon, several studies have attempted to indirectly assess the impact of air pollution on health. They had limitations and weaknesses and offered no recommendations regarding the sources and quality of data. The present analysis will be useful for BAPHE and for planning further studies.

Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole.

[Status epilepticus and gatifloxacin]. / Etat de mal épileptique et gatifloxacine.

INTRODUCTION: The epileptogenic potential of quinolones differs from one product to the other. The rare epileptic seizures induced by gatifloxacin were seen with the intravenous route. PATIENTS: We report two old ladies presenting with generalized status epilepticus after being treated orally with normal doses of gatifloxacin, with a good recovery. Past medical history of convulsion was the only factor found. Brain MR imaging was unremarkable. In one patient, EEG showed continuous bilateral paroxysmal discharges, predominantly frontal. CONCLUSION: Caution is warranted when using quinolones in elderly patients, especially those suffering from epilepsy.