Mucosal Immunity

The results of 3 new studies reveal unknown ways until now that COVID-19 spreads, leading scientists to urge the use of face coverings in public. Research from various parts of the world considered three separate factors in each study: low humidity, public restrooms and airborne dust. The implications from all three of these studies? Mask up!

Low Humidity

A study just published in Transboundary and Emerging Diseases confirms an earlier study conducted in the Greater Sydney, Australia area during the early stages of the pandemic that reported a link between low humidity and community spread of COVID-19. The new research led by Dr. Michael Ward in the Sydney School of Veterinary Science adds to the growing body of evidence that low humidity is a key factor in the spread of the Coronavirus. The scientists estimated that for a 1% decrease in relative humidity, COVID-19 cases increase by 7 to 8%. The same link was not found in other weather patterns such as rainfall, temperature or wind. According to Ward, dry air favors the spread of the virus: “”When the humidity is lower, the air is drier and it makes the aerosols smaller,” he said, adding that aerosols are smaller than droplets. “When you sneeze and cough those smaller infectious aerosols can stay suspended in the air for longer. That increases the exposure for other people. When the air is humid and the aerosols are larger and heavier, they fall and hit surfaces quicker.” These findings add to a growing body of research that recommends wearing a mask.

Public Restrooms

A second study conducted by Chinese researchers from Yangzhou University reported that flushing a public restroom toilet or urinal can release clouds of virus-laden aerosols that can be inhaled, posing a serious public health challenge. The scientists simulated and tracked virus-laden particle movements when toilets and urinals were flushed. They discovered that flushing involves an interaction between gas and liquid, resulting in a large spread of aerosol particles. The disturbing results revealed that the trajectory of the particles ejected from flushing showed that more than 57% of the particles traveled away from the urinal. The researchers further point out that when men use urinals in a public restroom, these tiny particles can reach their thigh within 5.5 seconds when compared to the toilet flush, which takes 35 seconds to reach slightly higher. “From our work, it can be inferred that urnial flushing indeed promotes the spread of bacteria and viruses,” said Xiang-Dong Liu, one of the study’s authors. “Wearing a mask should be mandatory within public restrooms during the pandemic, and anti-diffusion improvements are urgently needed to prevent the spread of COVID-19.”

Airborne Dust

A third study from the University of California, Davis and the Icahn School of Medicine at Mt. Sinai reported that influenza viruses can spread through the air on dust, fibers and other microscopic particles. Until now, scientists assumed airborne transmission occurred mainly due to respiratory droplets by coughing, sneezing or talking. The scientists examined whether tiny, non-respiratory particles could carry influenza between guinea pigs. Using an automated particle sizer to count airborne particles, they found that uninfected guinea pigs give off spikes of up to 1,000 particles per second as they move around the cage. Particles given off by the animals’ breathing were at a constant but lower rate. Immune guinea pigs with influenza virus painted on their fur could transmit the virus through the air to other, susceptible guinea pigs, showing that the virus did not have to come directly from the respiratory tract to be infectious. Next the researchers tested whether microscopic fibers from an inanimate object could carry infectious viruses. They treated paper facial tissues with influenza virus, let them dry out and then crumpled them in front of the automated particle sizer. Crumpling the tissues released up to 900 particles per second in a size range that could be inhaled. They were also able to infect cells from these particles released from the virus-contaminated paper tissues. According to the researchers, the surprising findings that dust can spread viruses have obvious implications for Coronavirus transmission and use of masks for protection. Plus, they said, it opens up an entire new field of investigation on how outbreaks are interpreted.

Original studies available in these sites:

https://doi.org/10.1063/5.0021450

https://doi.org/10.1038/s41467-020-17888-w

https://doi.org/10.1111/tbed.13766

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According to the researchers, including those from Ruhr University Bochum in Germany, high quantities of the virus particles, or viral load, can be detected in the oral cavity and throat of some COVID-19 patients.

Early and accurate detection is critical for preventing the spread of COVID-19 and providing appropriate care for patients. Nasopharyngeal (NP) swabs, which require inserting a long shaft into the nasal cavity to collect a sample from the back of the nose and throat, are currently the gold standard for collecting a specimen for diagnosis. But the procedure is technically challenging, often uncomfortable for patients and requires personal protective equipment that may be in short supply. Other approaches to collecting specimens—including from an oropharyngeal swab and sputum—have been tested in small studies, but there is uncertainty about which method is best for detecting the virus. In a new study published in EBioMedicine, investigators from Brigham and Women's Hospital conducted a systematic review and meta-analysis, analyzing data from more than 3,000 specimens to compare the three approaches. The team found that sputum testing detected the RNA of the virus that causes COVID-19 at significantly higher rates while oropharyngeal swab testing had lower rates. Regardless of the collection method, the earlier samples were collected after symptoms began, the higher the detection rate.

"The accurate diagnosis of COVID-19 has implications for health care, return-to-work, infection control and public health," said corresponding author Jonathan Li, MD, a faculty member in the Division of Infectious Diseases at the Brigham. "Our gold standard in and out of the hospital is the nasopharyngeal swab, but there's a lot of confusion about which sampling modality is best and most sensitive. Our study shows that sputum testing resulted in significantly higher rates of SARS-CoV-2 detection and supports the use of this type of testing as a valuable method for the diagnosis and monitoring of COVID-19 patients." Li and his colleagues scoured the literature—both preprints and published papers—for studies that assessed at least two respiratory sampling sites using an NP swab, oropharyngeal swab or sputum. From more than 1,000 studies, they identified 11 that met their criteria. These studies included results from a total of 3,442 respiratory tract specimens. The team examined how often each collection method produced a positive result. For NP swabs, the rate was 54 percent; for oropharyngeal swabs, 43 percent; for sputum, 71 percent. The rate of viral detection was significantly higher in sputum than either oropharyngeal swabs or NP swabs. Detection rates were highest within one week of symptom onset for all three tests.

Study Published in EbioMedicine (July 18, 2020):

https://doi.org/10.1016/j.ebiom.2020.102903

Coronavirus disease 2019 (COVID-19) first emerged in late 2019 in China.At the time of writing, its causative agent SARS-CoV-2 has spread worldwide i…...