In this post we summarize the results from three studies related to the COVID-19 pandemic, which we think would be of interest to our readers. Even though some of the findings aren’t new, they are important because they further support conclusions formed earlier during the pandemic. Other conclusions are preliminary glimpses on what we think may become important questions in the SARS-CoV-2-related research. We encourage our readers to have a look at the references within these papers and as always reach out to us with your ideas and opinions on the discussed topic.
Risks of dying from a SARS-CoV-2 are higher for older males.
There are some facts about the COVID-19 pandemic that are widely accepted by both scientists and the general public. One of the more obvious ones is that older people are at higher risk for developing severe SARS-CoV-2 infections. This trend was identified during the early stages of the pandemic. By now, a number of studies have confirmed this conclusion (Pastor-Barriuso et al., O'Driscoll et al.). These studies revealed that age is by far the strongest factor defining the person’s risk of dying from the coronavirus. This metric is known as the infection fatality ratio (IFR), which represents the proportion of people infected with the virus (including those who didn’t get tested or show symptoms) who will die as a result of the infection.
A schematic figure, not based on real data.
Something that wasn’t clear at the beginning of the pandemic is that men are more likely to die from the coronavirus than women. In fact, the risk of dying for infected elderly men is almost twice as high as for the same age group of women. Studies conducted in England and Spain revealed that men are more likely to die from a SARS-CoV-2 infection than women and this gap only increases with age.
Risks of dying from a SARS-CoV-2 are higher for older males.
Research articles and news outlets have repeatedly emphasized that airborne infectious diseases including the new coronavirus spread faster with coughing and sneezing. This is why the official guidelines provided by health organisations stress the importance of wearing a mask and sneezing or coughing in a sleeve, to reduce the potential transmission of the virus. However, sneezing and coughing are extreme instances that result in higher amounts of particles released in the air. When people breathe and speak, they may also release a high number of particles which tend to be too small to be seen by eye but big enough to carry viruses. A surprising but strangely logical feature of this new coronavirus is that people who speak loudly - even if they are wearing a mask - increase the risk of spreading the virus.
... people who speak loudly - even if they are wearing a mask - increase the risk of spreading the virus.
A new study published in Nature Scientific Reports demonstrated that the rate of particle emission during a normal human speech is positively correlated with the loudness of the voice, ranging from approximately 1 to 50 particles per second. The researchers tested four different languages (English, Spanish, Mandarin, or Arabic) and found that this trend remained valid regardless of the language. They also detected individuals releasing 10 times more particles than the average population. The ability of these “speech superemitters” to release more particles could not be fully explained by the voice loudness suggesting some unknown factors affecting the probability of the disease transmission. These factors are responsible for making certain individuals superspreaders who are disproportionately in charge of outbreaks.
Certain individuals - superspreaders - are disproportionately in charge of outbreaks
The same study demonstrated that speech potentially presents a greater danger than breathing. The main reason for this is that when we speak, we produce larger particles which could potentially carry more viruses which in turn increases the chances of infecting susceptible individuals. Another important implication of these results is that speaking in a loud voice may increase the amount of pathogen-containing particles and the rate at which an infected individual produces them. It means that airborne infectious diseases in general and COVID-19 in particular may spread faster in a school cafeteria, at a sporting event with fans cheering for their teams, and in noisy hospital rooms than in a library, quiet ward and other places where speaking in general and speaking loudly in particular isn’t the norm.
COVID-19 may spread faster in a school cafeteria or in a noisy hospital room than in a library, or a quiet ward where speaking loudly in particular isn't the norm.
We think that it raises an important question, is there a threshold after which the loudness of one’s voice takes over the mask protection and leads to a greater risk of infection compared to a situation where an individual isn’t wearing a mask but is speaking quieter? More studies are needed to fill the knowledge gap in this area and we at Pretty Light Science will be closely following the developments.
Sunlight and vitamin D may help fight SARS-CoV-2
A recent study demonstrated that the mortality of SARS-CoV-2 may be correlated with vitamin D levels (Tang et al.). Vitamin D is essential for a human body because it plays important roles in skeletal development, immune function and blood cell formation (WHO: The known health effects of UV). The intensity of vitamin D synthesis in our skin is closely related with exposure to UV radiation, meaning that the more UV radiation we get, the more vitamin D we produce. This link allowed the authors to propose a possible correlation between the UV radiation dose and the percent positivity of SARS-CoV-2. As with most of the COVID-19 related studies, the authors are cautious while making conclusions. They emphasize that the effect of the UV radiation dose on the mortality rate of COVID-19 may be very complicated. However, their preliminary results indicate that the UV radiation may have a negative correlation with COVID-19 infectivity during its early transmission period, and urge future research in this area.
A few previous studies support these conclusions suggesting that the magnitude of the COVID-19 pandemic may depend on various climatic factors, including the UV radiation intensity. For example, Sfîcă and colleagues demonstrated that severe COVID-19 outbreaks in some areas may be associated with lower UV radiation dose. Another recent study carried out by researchers in China showed a negative correlation between the number of infections and the latitude (Sun et al., 2020). Overall, these early studies suggest that the UV radiation dose may be linked with the intensity of SARS-CoV-2 transmission, thus playing an important role in the COVID-19 pandemic.
Some interesting observations were made in another recently published study investigating a potential link between the vitamin D levels and disease severity in COVID-19 patients (Mardani et al.). Vitamin D deficiency has been shown to be associated with various pathogens of the lower and upper respiratory tracts (Ginde et al., 2009). The authors demonstrated that the insufficient concentrations of vitamin D may be associated with the hospitalization of COVID-19 patients.
Data from Mardani et al., 2020
However, another recent study found no important links between blood vitamin D concentrations with COVID-19 risks (Hastie et al., 2020) making it clear that the research in this area should continue.
Conclusions
A number of important practical conclusions emerge from the papers described in this post. Even though everyone should be vigilant and follow recommended protective guidelines against the coronavirus, older males appear to be more at risk than other groups of people and thus they should be extra cautious and avoid unnecessary risks related to potential infections by the coronavirus.
Another important thing to remember is that if your colleagues or friends wear masks but speak louder than required in a meeting or at a social gathering (especially if it takes place in an enclosed space with no good ventilation), you may want to address this issue by mentioning the study discussed in this post. Or, if this doesn’t work, by moving further away.
Finally, a potential correlation between the COVID-19 mortality and the vitamin D deficiency may lead to health officials advising us to take vitamin D supplements. But as we mentioned above, further research is needed in this area.
Glossary:
Speech superemitters - individuals who emit up to ten times more particles when they speak than other people.
Vitamin D is a vitamin that is naturally present in a few foods, but is also produced when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis.
References:
The coronavirus is most deadly if you are older and male — new data reveal the risks. https://go.nature.com/34aWBWr
Aerosol emission and superemission during human speech increase with voice loudness. https://www.nature.com/articles/s41598-019-38808-z
Sunlight ultraviolet radiation dose is negatively correlated with the percent positive of SARS-CoV-2 and four other common human coronaviruses in the U.S. https://bit.ly/33Qya06
Association of vitamin D with the modulation of the disease severity in COVID-19. https://bit.ly/3hZ3AXk.
Are there beneficial effects of UV radiation? https://bit.ly/32Ws7ba
Vitamin D concentrations and COVID-19 infection in UK Biobank. https://bit.ly/3kOKSn3
SARS-CoV-2 infection fatality risk in a nationwide seroepidemiological study. https://bit.ly/308fUhT
Age-specific mortality and immunity patterns of SARS-CoV-2 infection in 45 countries. https://bit.ly/32ZFVl4
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