Research news in brief

Risk of SARS-CoV-2 aerosol transmission to health care workers

New research published in Anaesthesia may challenge the guidance that special aerosol precautions are only needed when using oxygen therapies for COVID-19 patients, and raises concerns about safety of staff and patients on hospital wards if they are not protected from infectious aerosols. The researchers built a novel chamber providing extremely clean air, in which 10 healthy volunteers sat. They breathed into a large cone and the researchers collected the particles that were breathed out and used a specialised machine, called an optical particle counter, to measure the number and size of the particles. In contrast to previous studies, the researchers collected almost all particles breathed out and this enabled a clear comparison between the amounts of aerosols generated by respiratory activities and oxygen therapies. First, the volunteers performed respiratory activities including breathing, talking, shouting, coughing and exercising, designed to mimic respiratory activity of patients with respiratory infections such as COVID-19. This showed that increased respiratory activity (such as coughing and deep breathing), which is common in patients with COVID-19, increases aerosols by more than 100 times. The volunteers then repeated the experiments while receiving oxygen therapies commonly used in hospitalised patients with severe COVID-19, first the delivery of oxygen at high flow into the nose (high flow nasal oxygen) and then oxygen delivered under pressure through a tight-fitting facemask (non-invasive ventilation). Aerosol numbers were not increased and, during increased respiratory activities, were reduced. Much current guidance is designed to protect health care workers from droplets, and infection spread by aerosols is only considered a risk when caused by medical therapies. In this new study, the volunteers produced up to 100 times more aerosol particles with activities such as coughing than they did during treatment with oxygen therapies, bringing into question current guidelines that state health care staff looking after patients with COVID-19 who are coughing and have breathing difficulty only need personal protective equipment that protects against the larger droplets. Droplet protection includes surgical masks but does not prevent aerosol particles passing around the edges of the masks and being inhaled. N95/FFP3 respirators, which are tightfitting and filter better, block more aerosols, but guidelines currently recommend these only for staff looking after patients receiving advanced oxygen therapies.

Stark economic reality of biological invasions

An analysis, published in Nature, has revealed the stark US$1.28 trillion economic damage caused by the world’s invasive species over the past 50 years, with a group of global experts warning damage and management costs will soar unless biodiversity agencies can improve prevention and control of biological invasions. The research shows invasive species have damaged crop yields, critical national infrastructure, and human health and diverted billions in taxpayer dollars annually, but too little is being done because the impact isn’t well recognised by decision makers and the public. Biological invasions take place when species of animals, plants and pathogens are deliberately or accidentally introduced in regions not previously occupied by these species. The researchers analysed thousands of costs estimates and used models to estimate the annual losses of US$26.8 billion between 1970 and 2017 caused by invasive species. They highlight the importance of addressing rapidly rising expenses of up to US$162 billion in 2017, which are set to rise into the trillions in coming years because of the increase of biological invasions. Emerging diseases such as COVID-19 were not included. “We found that costs roughly doubled every 6 years, a pattern that mimics the continuous increase in the number of alien species worldwide,” the authors wrote. One of the most contemporary examples is the ambitious Belt and Road Initiative by China that will open avenues for the introduction of new species around the world.

Dynamic model of SARS-CoV-2 spike protein reveals potential new vaccine targets

A new, detailed model of the surface of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein reveals previously unknown vulnerabilities that could inform development of vaccines, according to findings published in PLOS Computational Biology. A key feature of SARS-CoV-2 is its spike protein, which extends from its surface and enables it to target and infect human cells. Extensive research has resulted in detailed static models of the spike protein, but these models do not capture the flexibility of the spike protein itself nor the movements of protective glycans — chains of sugar molecules — that coat it. To support vaccine development, the researchers aimed to identify novel potential target sites on the surface of the spike protein. To do so, they developed molecular dynamics simulations that capture the complete structure of the spike protein and its motions in a realistic environment. These simulations show that glycans on the spike protein act as a dynamic shield that helps the virus evade the human immune system. Similar to car windshield wipers, the glycans cover nearly the entire spike surface by flopping back and forth, even though their coverage is minimal at any given instant. By combining the dynamic spike protein simulations with bioinformatic analysis, the researchers identified spots on the surface of the spike proteins that are least protected by the glycan shields. Some of the detected sites have been identified in previous research, but some are novel. The vulnerability of many of these novel sites was confirmed by other research groups in subsequent laboratory experiments. “We are in a phase of the pandemic driven by the emergence of new variants of SARS-CoV-2, with mutations concentrated in particular in the spike protein,” the researchers wrote. “Our approach can support the design of vaccines and therapeutic antibodies, especially when established methods struggle.” The method developed for this study could also be applied to identify potential vulnerabilities of other viral proteins.

Factors that may predict next pandemic

Humans are creating or exacerbating the environmental conditions that could lead to further pandemics, according to Australian research published in Transboundary and Emerging Diseases. The global human population has increased from about 1.6 billion in 1900 to about 7.8 billion today, putting pressure on ecosystems. The authors used 13 892 unique pathogen–country combinations and 49 socio-economic and environmental variables from 190 countries to identify country-level factors predicting three categories of disease: zoonotic, emerging (newly discovered diseases or those diseases that have increased in occurrence or occurred in new locations) and human. Factors predicting zoonotic disease diversity were land area, human population density, and area of forest, with high zoonotic disease diversity found in Europe, North America, Latin America, Australia and China. Factors predicting emerging diseases were  land area, human population density and the human development index. Areas with high emerging disease diversity include Europe, North America, Latin America, and India. Among the factors predicting human diseases were  high per capita health expenditure, mean annual temperature, land area, human population density, human development index and rainfall. Areas with high human disease diversity include North America, Latin America, China and India.