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Love in the times of covid how dating apps have adapted to the current environment
To determine the factor triggering the sudden surge of daily new COVID cases arising in most European countries during the autumn of The study proves no correlation between the country surge date and the 2 weeks preceding temperature or humidity but shows an impressive linear correlation with latitude. Introducing reported seasonal blood hydroxyvitamin D 25 OH D concentration variation into the reported link between acute respiratory tract infection risk and 25 OH D concentration quantitatively explains the surge dynamics.
However, by comparing different patient populations, discriminating whether a low 25 OH D concentration is a real factor underlying COVID severity or only a marker of another weakness that is the primary severity factor can be challenging. The date of the surge is an intrapopulation observation and has the benefit of being triggered only by a parameter globally affecting the population, i.
The indicate that a low 25 OH D concentration is a contributing factor to COVID severity, which, combined with studies, provides a convincing set of evidence. All curves exhibit a clear surge in the growth rates. A commonly reported explanation is the decreasing temperature. The aim of this study is to challenge this assumption against a pure latitude impact. For each country, an airport close to the PWC was chosen see supplementary Excel file. The average temperature and humidity were computed between 8h00 to 20h00, outside this period, the population is mostly indoors.
The theoretical sun UVB daily dose for vitamin D production, as a function of latitude and of the day of the year, was derived from the digitalization of Fig. All these data are in the supplementary Excel file. The date of the surge was automatically determined by fitting the two last months of the daily new COVID cases with the empirical model:. This further allows us to prevent overfitting of the data noise by a steepness tuned for each country.
Note that as the exponential coefficient varies with time, the doubling time around the surge date is not simply ln 2 divided by this coefficient. To evaluate the impact of UV insolation on the new daily case dynamics, we consider the simple model:. The solution of Eq.
If the contagiousness is constant, the daily new cases follow a monoexponential increase or decrease:.
In both graphs, the corresponding date runs from left to right. In both integrations, k 0 was fitted to obtain a typical threefold increase in the last 10 days see Fig. Black curve: mono-exponential curve. A meta-analysis of 24 studies reporting the association between 25 OH D concentration and the risk or severity of acute respiratory track infection ARTI during cold or influenza epidemics 3 shows that the risk follows a power-exponential relation Fig.
Assuming that COVID risk similarly depends on 25 OH D concentration and considering this risk increase as the single effect varying k twe obtain. Figure 2 D shows the corresponding daily new case Eq. This standard deviation could still be higher in the country population with the presence of older and chronically ill subjects.
Table 2 shows the fitting all data and fitting processes are provided in the supplementary xlsx file. Although that the parameters are accurately measured, they suffer from the limitations that, besides the latitude, they are not population weighted.
Table 3 shows the reinforcement implemented during September and October of the existing safety measures see country s in Excel file to see the intensity level of each safety measure. With regard to the delay between infection and contagiousness of a subject, only two reinforcements in bold could have delayed the surge date.
The abundance of measured reinforcements within the two weeks following the surge date provides evidence of the surge threat. Figure 3 A,B clearly prove no correlation with temperature or humidity, while Fig. COVID surge date as a function of country mean temperature A and humidity B during the 2 preceding weeks and as a function of country PWC latitude Cpointing to vitamin D as one of the primary factors flags link countries between graphs.
Figure 4 clearly shows that the surge dates set on the sun UVB daily dose as a function of latitude demonstrate an impact of the sun UVB daily dose. Black circles: country surge dates positioned on their corresponding latitude curve. Trendline forced to intercept 0,0.
Many studies support an impact of low 25 OH D concentrations on respiratory impairment in coronavirus or viral diseases 9 and recently on the COVID pandemic as well see 10 for a detailed review and polish of 14 studies reporting such impacts. Low 25 OH D concentrations are also more prevalent in populations at risk, i. However, by comparing COVID severity between different populations, determining whether the 25 OH D concentration is a real factor of COVID severity or only a marker of another weakness that is the primary severity factor can be challenging. The date of the surge is an intrapopulation observation and has the benefit of being triggered only Corona a parameter globally affecting this population.
There is no correlation with temperature, humidity, or school opening dates see Excel filebut there is an impressive latitude correlation Fig. The remaining common parameter affecting these populations monotonically at different times depending on latitude is the sun UV daily dose Fig. This UV index dependence was already observed for influenza epidemics 16although the temperature dependence appeared more important. A global seasonality study also evidenced a monthly correlation between other pre-existing human seasonal coronavirus activities and temperature and dating However, this study did not consider latitude as a confounding factor, and on a monthly scale, there is a correlation between temperature-humidity and latitude.
On the daily scale used the the present study, this correlation no longer exists as each country is temporally affected by different wind directions. This feature allows us to clearly discriminate between temperature-humidity and latitude impacts.
However, many European countries were able to break the surge in November by implementing additional safety rules. Activities where people dating wear face masks, such as collective sports or relaxation in pubs and restaurants, were forbidden, and festive activities where people often forget distancing recommendations were forbidden. In contrast, the population continued their professional and outdoor relaxing activities wearing face masks at work, in public transport, in itinerant outdoor markets European use and in parks.
The success of these rules supports the major role of airborne transport of SARS-CoV-2 versus contamination by outdoor contact with infected material. Indeed, Fig. In contrast, Fig. Another feature discards the potential role of solar UV inactivation: in Europe, people spend the majority of their time indoors, so even if contact with a contaminated surface can be the source of transmission, the contact probability is lower outdoors than indoors where solar UV inactivation is absent.
This is in line with a one week recent study showing that outdoor contamination is much less frequent than indoor ones The positive linear slope of the sun UVB threshold versus the country latitude Fig. As a result, skin vitamin D production in northern populations is affected by the sun UVB decrease in a slower manner than that of the southern populations. The present study thus suggests that a low 25 OH D concentration is a contributing factor of COVID severity, as already shown by studies 10which together constitute a convincing bundle of evidence.
By increasing the coronavirus load in the respiratory tract, the contagiousness in the population is also increased, starting a chain reaction that explains the wave surge. This study has three strengths. The utilisation of the date of the surge is not dependent on the differences between the safety measures implemented in the countries but can only depend on the change in a global parameter affecting the whole country population.
The correlation analysis on a daily scale prevents polish interpretation from being blurred by the seasonal latitude-climate correlation existing on a monthly scale. Using the relation reported between ARTI and 25 OH Corona concentration together with the reported seasonal 25 OH D concentration variation, the derived prediction of the daily new case slope increase is in line with the observation.
The study has several weakness. Some countries have a homogeneous population distributed at a few latitudes, such as France, Germany, and Russia, which could twist or blur the correlation. Access to reported regional new daily cases should be very valuable. The surge intensity analysis was performed using the 25 OH D concentration reported in a small volunteer cohort.
Observed autumn 25 OH D concentration decrease for several countries should be helpful to further increase the confidence in the vitamin D status contribution. Measures to reduce the pandemic severity during the coming winter using controlled preventive vitamin D supplementation should be considered 10 Grigalavicius, M. Biologically efficient solar radiation: Vitamin D production and induction of cutaneous malignant melanoma.
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Article Google Scholar. Herman, J. Air Qual. Google Scholar. Pham, H. Acute respiratory tract infection and hydroxyvitamin D concentration: A systematic review and meta-analysis. Public Health. Klingberg, E.