To determine how many viruses fall from the troposphere each day, automatic collectors were placed at two different locations in the Sierra Nevada Mountains of Spain at 1.75 km above sea level. Placing the collectors at this height allows sampling of air above the atmospheric boundary layer (pictured – image credit). Samples were retreived every 1-2 weeks over the course of two years and analyzed for the presence of viruses by flow cytometry after purification by centrifugation.

The results show that billions of viruses fall from the atmosphere each day: from 0.3 to 3.8 x 109 per square meter. Most (69%) of the viruses that descend from the atmosphere are attached to dust or organic aggregates. The rate of falling viruses was not substantially different over the course of the study nor between the two different sites.

Here, we provide an overview of recent technology for imaging cells and viruses by light microscopy, in particular fluorescence microscopy in static and live-cell modes. The review lays out guidelines for how novel fluorescent chemical probes and proteins can be used in light microscopy to illuminate cells, and how they can be used to study virus infections. We discuss advantages and opportunities of confocal and multi-photon microscopy, selective plane illumination microscopy, and super-resolution microscopy. We emphasize the prevalent concepts in image processing and data analyses, and provide an outlook into label-free digital holographic microscopy for virus research.

short highly conserved termi

Previous studies suggested that the Middle East respiratory syndrome coronavirus (MERS-CoV) may have originated in bats. However, its evolutionary path from bats to humans remains unclear. In this study, we discovered 89 novel lineage C betacoronaviruses (BetaCoVs) in eight bat species. We provide the evidence of a MERS-related CoV derived from the great evening bat that uses the same host receptor as human MERS-CoV. This virus also provides evidence for a natural recombination event between the bat MERS-related CoV and another bat coronavirus HKU4. Our study expands the host ranges of MERS-related CoV and represents an important step toward establishing bats as the natural reservoir of MERS-CoV. These findings may lead to improved epidemiological surveillance of MERS-CoV and the prevention and control of the spread of MERS-CoV to humans.

Stabell et al. have revealed why human dengue viruses do not replicate to high titres in primate models. They found that the stimulator of interferon genes (STING) protein, which induces the production of type I interferon in infected cells to reduce viral titres, is cleaved by the dengue virus protease NS2B3 in humans but not in key primate models. STING cleavage occurred at an RG motif at amino acids 78 and 79, decreasing markers of an innate immune response and increasing viral replication in human cells. The analyses of STING sequences from all placental animals in Genbank, as well as from 16 non-human primate cell lines, revealed that only STING from three small apes and three small rodents encodes this RG motif. As introducing this RG motif into STING from rhesus macaque, marmoset and mouse rendered it susceptible to cleavage by dengue virus NS2B3, engineering model organisms so that their STING contains this motif could enhance the study of dengue viruses in animals.