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\begin{document}

\title{Some questions of epidemiology, statistics, and pandemic forecast
COVID-19.}



\author[1]{Shamil Timerbulatov}%
\author[1]{Vil Timerbulatov}%
\author[1]{Makhmud Timerbulatov}%
\affil[1]{Bashkir State Medical University}%


\vspace{-1em}



  
  \date{May 23, 2024}


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\selectlanguage{english}
\begin{abstract}
The article analyzes the indicators of prevalence, morbidity, lethality
and mortality in the new coronavirus disease - COVID-19, based on this
specialized literature and official information from the state mass
media. The importance of correct application of the principles of
medical statistics for the analysis of these indicators in
decision-making on the introduction of restrictive measures, monitoring
the epidemic process, evaluating the effectiveness of these measures and
the activities of medical organizations is shown. Individual pandemic
forecast models are considered.%
\end{abstract}%



\sloppy


Some questions of epidemiology, statistics, and pandemic forecast

COVID-19.

Prof. Vil M. Timerbulatov, MD, Shamil V. Timerbulatov, MD, Prof. Mahmud
V. Timerbulatov, MD.

Bashkir State Medical University, str. Lenin, 3, Ufa, Russian
Federation. 450008.

Professor Vil Mamilovich Timerbulatov -- head of surgery department in
Bashkir State Medical University, Ufa, Russian Federation; head of
Surgery Emergency Clinic, Ufa, Russian Federation;
https://orcid.org/0000-0002-1696-3146;

Professor Shamil Vilevich Timerbulatov -- PhD, surgery department in
Bashkir State Medical University, Ufa, Russian Federation; deputy head
of Clinic for Infection Diseases, Ufa, Russian Federation;
https://orcid.org/0000-0002-4832-6363; e-mail:\emph{timersh@yandex.ru};
phone: +79273073333;

Professor Makhmud Vilevich Timerbulatov -- head of surgery department in
Bashkir State Medical University, Ufa, Russian Federation; head of
Surgery Emergency Clinic, Ufa, Russian Federation;
https://orcid.org/0000-0002-6664-1308.

Number of words 5634.

The article analyzes the indicators of prevalence, morbidity, lethality
and mortality in the new coronavirus disease - COVID-19, based on this
specialized literature and official information from the state mass
media. The importance of correct application of the principles of
medical statistics for the analysis of these indicators in
decision-making on the introduction of restrictive measures, monitoring
the epidemic process, evaluating the effectiveness of these measures and
the activities of medical organizations is shown. Individual pandemic
forecast models are considered.

Since the World Health Organization's announcement on 11 March 2020 of a
new coronavirus disease pandemic, COVID-19, many reports of illness,
especially deaths, from the media, social networks, have triggered a
stormy, mixed public reaction and often fueled fear and depression in
people.

In statistical processing of medical articles, packages of statistical
programs are used, based on probability theory and mathematical
statistics {[}1{]}, i.e., in fact, the techniques of ''medical
statistics'' are used. The complexity of statistical analysis of medical
data is caused by a number of objective and subjective factors, such as
specific standards in research design, the presence of legal, economic,
ethical restrictions, the great complexity of the studied phenomena, the
presence of ''leads'' and confusing factors, the most frequently solved
problems do not completely coincide with those in other subject areas.

In the first month of the pandemic, official information from WHO and
all countries reported numbers of people infected and dead (in absolute
figures), with shocking effects on the population, although these
figures did not reflect the status, course or trends of the epidemic.
Such uncertainty in the assessment of the situation, especially
ignorance of trends in the spread of COVID-19, could not contribute to
the adoption of correct, justified, especially preventive decisions by
the authorities, public health leaders, at least in the near future.

As of May 26, 2020 COVID-19 in the world 5,603,427 people got sick,
350,041 died, in the Russian Federation 362,342 and 3,807 respectively.
The mortality rate for this infection in the world is 6.5\%, the share
of the infected population is 0.06445\%, in Russia it is 0.96\% and
0.22\% respectively.

A pandemic occurs when 1 to 5\% of the population is affected, but given
the characteristics of the COVID-19 coronavirus, WHO has declared a
pandemic with lower infection rates.

Up to 60\% of those tested in Russia have the coronavirus without
symptoms. The results of antibody testing of the population in Santa
Clara County, California, showed that the morbidity was 50-85 times
higher than the official one and, accordingly, the mortality rate was
also 50-85 times lower and was 0.04-0.07\% instead of 4\%.

It is important to clearly distinguish between lethality (\% of all
deaths) and mortality, which is calculated on 1,000 or more often on 100
thousand population.

Every year 1.2 million people die from pneumonia alone, 350,041 died
from coronavirus between the end of December 2019 and 26 May 2020, but
the difference between dying with coronavirus and dying from coronavirus
must also be considered. The vast majority of those who died suffered
from cancer, chronic lung disease, obesity, diabetes, and cardiovascular
disease, and the virus was the last straw during their illnesses.

According to Rospotrebnadzor (Russian Federal Service for Supervision of
Consumer Rights Protection and Human Health), following the results of
the influenza and acute respiratory infections epidemic in 2016-2017,
the daily number of cases in Russia was 120 thousand people, which is
significantly higher than COVID-19 (from 5 thousand to 10 thousand per
day). Therefore, rather, the peak of the epidemic in Russia was passed 2
months ago, when there was no testing due to the total hospitalization
of all infected people in hospitals, the latter have become real centers
of the hospital epidemic (in 55\% of centers in medical organizations),
the expansion of indications was influenced by the increase in the cost
of payment for medical insurance up to 200 thousand rubles per case.
With the further mass conversion of medical organizations into
infectious disease hospitals, the latter are loaded only by 30-35\%.

On 15 January 2019 WHO announced a list of 10 major threats to human
health in 2019, including air pollution and related climate change,
Ebola, the global influenza pandemic, HIV and increased resistance of
bacteria to antibiotics.

Every year, air pollution leads to the premature death of 7 million
people.

Non-communicable diseases such as diabetes, cancer, and cardiovascular
diseases are the second most dangerous, with 4 million people dying from
them every year (7\% of all deaths).

As of 31 January 2020, 213 people worldwide had died infected with
COVID-19. During this period, 684,497 people died of cancer, 633,508
children under 5 years old, 140,112 suicides, 81,757 of malaria, 70,189
of contaminated water, 40,452 of influenza, 25,763 during childbirth.

As of March 11, 2020, the total number of COVID-19 infections in the
world exceeded 118 thousand in 114 countries, according to WHO, 4,291
people died. Most of the infected were found in Italy
(\textgreater{}10,000), Iran (9,000 cases, of which almost 1,000 died),
South Korea (7,700, 242 died), and the Russian Federation had 20
infected, so at the beginning of the pandemic the global mortality rate
from COVID-19 was 3.63\%, in Iran - 11.1\%, South Korea - 3.14\%, in
Russia - 0\%.

Subclinical or mild forms of coronavirus disease were observed in 80.9\%
of patients, but they had the potential for virus spread {[}2{]} and had
the same viral load as patients with symptoms of SARS-CoV-2 {[}3{]}.

According to WHO, the incubation period is 5.2 days with a range of 1-14
days {[}4{]}.

The average time for patients to see a doctor from the onset of symptoms
is 5.8 days, and 12.5 days before hospitalization {[}5{]}.

The stages of symptomatic disease were classified on the basis of
non-contrast CT results and divided into early (0-4 days), progressive
(5-8 days), peak (9-13 days) and adsorption (\textgreater{}14 days)
stages {[}6{]}.

Subpleural opacities (GGOs) located in the lower lobes of the lung are
detected at an early stage of the disease. Bilateral spread of the
infection process and diffuse subpleural turbidity are detected in the
progression stage. At the peak stage, the presence of dense
consolidation, residual parenchymatous strips are determined. The
adsorption stage can last more than 26 days, with a more controlled
process, gradual resolution, and signs of recovery {[}6{]}.

In a prospective cohort study of 1,150 COVID-19 patients hospitalized in
New York City, it was shown that more than \selectlanguage{ngerman}¾ of the severely ill
patients needed a ventilator and almost 1/3 needed hemodialysis {[}7{]}.
Of the patients in critical condition, 39\% died, and 41\% received
invasive mechanical ventilation.

According to the National Health Service of England, Wales and Northern
Ireland (11,292 patients needed intensive care), 50\% of patients who
received a ventilator died within 40 days after starting intensive care
{[}8{]}.

In the United States, at the beginning of the pandemic, there were
95,000 intensive care and resuscitation beds (28.7 beds per 100,000
population). In Russia there is no exact data, their number, according
to different sources, varies from 12 thousand to 35 thousand (8.57-35.0
per 100,000 population).

The number of COVID-19 intensive care beds also varies greatly in
different countries from 22.9 beds 100,000 population in Germany, 28.9 -
Austria, 16.3 - France, 12.9 - Canada, 10.5 - UK, 9.7 - Spain. 8.6 -
Italy, 7.8 - Denmark, 5.0 - Ireland.

In 2016, there were 197 million pneumonia cases worldwide and 1,200,000
died.

In 2017, according to the Federal State Statistics Service, over 671
thousand people suffered from pneumonia in Russia, and 26 thousand died.
26,088 died in 2017, 25,642 people died in 2018.

In 2019, 1.8 million people died from various causes in Russia, 1.67
million died directly from diseases, and 130 thousand died from external
causes.

In Russia, every year respiratory diseases (influenza, acute respiratory
infections, pneumonia) are carried by \selectlanguage{english}[?]50 million people.

According to WHO, there are \selectlanguage{english}[?]1 billion influenza cases worldwide every
year, including 3-5 million severe cases and from 300 to 650 thousand
deaths.

Table 1.

Rates of morbidity and mortality of new coronavirus infection COVID-19
in different countries (as of 30.05.2020)\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Country\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Density of population per square kilometer\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Incidence per 100,000 population\strut
\end{minipage} & \begin{minipage}[b]{0.24\columnwidth}\raggedright\strut
Lethality (in \%)\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Russia\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
9\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
283.2\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
1.14\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
USA\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
32\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
540.3\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
5.86\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Italy\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
193\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
387.0\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
14.3\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Spain\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
92\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
620.8\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
10.06\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
France\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
118\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
281.7\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
15.20\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Great Britain\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
255\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
484.2\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
14.07\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Germany\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
230\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
220.48\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
4.69\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Brazil\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
23.6\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
223.0\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
5.96\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Turkey\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
100\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
195.3\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
2.76\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
China\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
650\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
6.0\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
5.5\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
In the world\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
12\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
85.22\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
6.09\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Norway\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
13\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
157.09\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
2.8\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
Sweden\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
20\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
1060.0\strut
\end{minipage} & \begin{minipage}[t]{0.22\columnwidth}\raggedright\strut
11.84\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

It can be noted from the presented data (Table 1) that there is no
unambiguous dependence of morbidity and detail indicator on population
density.

Experience with the COVID-19 pandemic since 11 March 2020 shows that
countries that introduced severe restrictive measures early in the
epidemic have significantly reduced or stabilized their infection
(morbidity) rates. Such countries include China, Russia, Germany, Norway
(morbidity per 100,000 population \textless{} 300 people), and the
countries that followed a ''liberal approach'' to restrictive measures
had morbidity rates above 300/100,000 population (Italy, Spain, United
Kingdom). The absence of practically restrictive measures has led to a
significant increase in the incidence of diseases, as happened in Sweden
(\textgreater{}1,000/100,000 population).

There are other reasons for fluctuations in the incidence rate. These
include the loyalty of the population to the authorities, the
implementation by the vast majority of the population of measures aimed
at preventing the spread of infection. The need for mandatory
implementation of recommendations by citizens should be accompanied by
informing the population about the causes of the spread of infection and
possible consequences of the disease. It is important to have truthful
information based on the opinions of medical scientists, the maximum
exclusion of pseudo-scientific, previously false information about the
infection. The third aspect of this problem is the development of a
control system and analysis of the implementation of restrictive
measures. The state solves this issue in different ways and there can be
no right recipes for everyone.

In addition, long-term restrictive measures of isolation of citizens
cause fatigue, which leads to disregard for social distances, wearing
masks.

Rating of countries on the number of deaths from coronavirus infection
as of 18.04.2020 led the U.S., Britain, Italy, France, Spain, but in
calculating mortality - the situation is different. Belgium (16.37\%),
France (16.64\%), Great Britain (14.17\%), Italy (14.15\%), Hungary
(13.07\%), Netherlands (12.90\%), Sweden (12.21\%), Spain (11.95\%),
Mexico (10.52\%), USA (5.1\%), Germany (3.07\%), Brazil (6.3\%), Turkey
(2.16\%), China (5.46\%), Norway (1.31\%), Russia (0.94\%).

Table 2.

Comparative lethality rates in some countries for 18.04.2020 and
30.05.2020.\selectlanguage{english}
\begin{longtable}[]{@{}lll@{}}
\toprule
Country & Mortality rates (in \%) & Mortality rates (in
\%)\tabularnewline
\midrule
\endhead
& On 18.04.2020 & On 30.05.2020\tabularnewline
Russia & 0.94 & 1.14\tabularnewline
USA & 5.1 & 5.86\tabularnewline
Italy & 14.15 & 14.3\tabularnewline
Spain & 11.95 & 10.06\tabularnewline
France & 15.64 & 15.20\tabularnewline
Great Britain & 14.17 & 14.07\tabularnewline
Germany & 3.07 & 4.69\tabularnewline
Brazil & 6.3 & 5.96\tabularnewline
Turkey & 2.16 & 2.76\tabularnewline
China & 5.46 & 5.5\tabularnewline
Norway & 1.31 & 2.80\tabularnewline
Sweden & 12.21 & 11.84\tabularnewline
\bottomrule
\end{longtable}

In most countries, there has been virtually no marked change in
mortality rates, some increase in mortality in the USA (from 5.1 to
5.86\%), Germany (from 3.07 to 4.69\%), Norway (from 1.31 to 2.8\%), was
statistically unreliable (OR: 0.833 (95\% CI, 0.262-2.642), p=0.756;
0.600 (96\% CI, 0.147-2.433), p=0.475; and 0.33 (95\% CI, 0.35-3.150),
p=0.337) respectively.

The persistence of a stable level of lethality in coronavirus disease
seems to be due to the difficulties of etiopathogenetic treatment of
this viral infection. The existing methods of medical treatment are
extremely variable, the drugs used were mostly recommended by the
principle of ''repositioning'' drugs and imply the search for drugs for
the treatment of a new disease among the substances already studied in
clinical trials or used in clinical practice {[}9{]}. Almost to this
day, there are no drugs whose effectiveness has been proven by the
results of randomized controlled trials and meta-analyses. An example is
the recent WHO recommendations not to use chloroquine/hydroxychloroquine
that are not based on strong evidence in the treatment of coronavirus
disease. 96,032 patients with COVID-19 from 20.12.2019 to 14.04.2020
were analyzed for the effectiveness of treatment in 671 hospitals on 6
continents {[}10{]}.

10,698 (11.1\%) of them died in hospitals, 14,888 patients formed 4
groups: within 48 hours after diagnosis, they began receiving
chloroquine (1,868), chloroquine with macrolides (3,783),
hydroxychloroquine (3,016) and hydroxychloroquine with macrolides (6,221
patients). 81,144 patients did not receive treatment for any of the
schemes made up the control group. In the control group, the mortality
rate was 9.3\%, in the group receiving hydroxychloroquine - 18\%,
hydroxychloroquine with macrolides - 23.8\%, chloroquine - 16.4\%, and
chloroquine with macrolides - 22.2\%.

Scientists from South Korea have screened about 3,000 approved drugs and
found substances potentially effective against SARS-CoV-2 and considered
niclosamide and cyclosonide the most promising {[}9{]}. The genomes of
SARS-CoV and SARS-CoV-2 viruses coincide by 79.5\% , and therefore the
authors suggested that drugs that suppress SARS-CoV may also be
effective against SARS-CoV-2 {[}57{]}.

Out of 3,000 molecules, 35 were identified that inhibit SARS-CoV-2. In
the course of the experiment Vero cell culture (normal kidney cells of
African green monkey) was treated with the drug, and then infected with
SARS-CoV-2. 24 hours after the infection the immunofluorescent cell
analysis was carried out with antibody that recognized SARS-CoV-2
nucleo-capsid protein - it was identified as the most significant 2
medications. Niklozamide, an antihelminthic drug used in tapeworm
infestation, was very active against SARS-CoV-2 (IC50 semi-maximum
inhibition concentration - 0.28 \selectlanguage{greek}µ\selectlanguage{english}M) and was effective against a wide
range of viruses, including SARS-CoV and MERS-CoV. Ciclesonide, an
inhaled corticosteroid, is used to treat bronchial asthma and allergic
rhinitis, although its activity was significantly lower against
SARS-CoV-2 (IC50 - 4.33 \selectlanguage{greek}µ\selectlanguage{english}M).

Possible reasons for the lack of reduction in mortality can be a gradual
reduction in the resources of medical organizations, health care in
general, the growing shortage of medical personnel due to their
morbidity, mortality, physical, moral and psychological fatigue, lack of
proper material and moral support.

In April, the unemployment rate in Sweden reached 7.9\%, excluding
seasonal factors - 8.2\%. Bloomberg analyst Johanna Jeneson forecasts
that unemployment will rise to 17\%. Thus, the Swedish economy, which
refused to impose a strict quarantine, did not help.

Analysts of the Financial Times, comparing the mortality during the
pandemic in 13 countries in March-April 2020 with the average for the
same period in 2015-2019, noted an increase of 49\% in 2020: in France
34\%, Italy 90\%, the Netherlands 40\%, Spain 51\%, Belgium 60\%, Sweden
only 18\%.

But according to countrymeters.info, in January-March 1,580 people per
day died, in 2019 - 1,586 people per day. In USA in the first three
months of 2020, 4,477 people died per day, and in 2019 - 7,458 people
died per day. Spain - 1,098 and 1,105, Germany - 2,400 and 2,410, Russia
- 5,538 people per day (including from COVID-19 - 450 people) in 2020
and 5,563 people per day in 2019.

The infection rate in the Russian Federation in the middle of March was
at the level of 3, 15 May - 0.9, for a full economic life 0.5 is
required. As of May 15, 2020 in 28 regions the coefficient was
\textless{}1, in 9 - about 3.

Hospitalized on May 20, 2020 in Russia - 109 thousand people, 2,500 - in
the ICU. By severity: heavy - 4.2\%, medium - 34.9\%, light - 60.9\%. Of
the specialized 165,290 beds, 110 thousand (66\%) are used, 92\% of the
beds with ventilators are not occupied. Thus, 2.29\% of patients with
COVID-19 were hospitalized for intensive care and resuscitation. On the
one hand, the high percentage of unused, especially expensive beds is a
serious, additional burden on health care, which certainly contributes
to growth, ''accumulation'' of patients waiting for planned, especially
surgical treatment. But on the other hand, the complexity and
unpredictability of the epidemiological process, the emergence of new
outbreaks, justifies the over-deployment of infectious beds, at least
until the infection rate \textless{} 1.0, after the ''plateau'' of
morbidity has been completed and the decline began.

By 25 May 2020, 3,807 people had died from COVID-19 in Russia, which
would have been about 14.64\% of all deaths in 2019 in Russia due to
pneumonia (26,000).

In 2019, the total mortality rate in the Russian Federation from all
diseases was 1.2\%, and from coronavirus during the pandemic period was
0.98-1.05\%. Thus, in the structure of total lethality, deaths from
coronavirus may be 0.21\% (3,807 deaths from COVID-19 as of 26.05.2020
for a total of 1,800,000 deaths in 2019).

Concomitant diseases and infections lead to an increase in the severity
of respiratory viral infections and mortality {[}11{]}. Most deaths
during the 1918 influenza epidemic were caused by subsequent bacterial
infection, especially Streptococcus pneumonia {[}11{]}.

Poor outcomes of the 2009 H1N1 flu pandemic were also associated with
subsequent bacterial infections {[}12{]}.

In the current COVID-19 pandemic, 50\% of patients who died had
secondary bacterial infections {[}13{]}, with both bacterial and fungal
infections reported {[}14{]}.

Patients with COVID-19 are on an invasive ventilator for a long time (on
average, 9.1 days), which increases the likelihood of developing
hospital- and ventilator-associated infections.

It is important to prevent the second wave of the epidemic, which is
predicted by many virologists in autumn-winter 2020.

In Berlin, scientists suggest tightening the quarantine at 30 newly
infected per week, then the extreme color of the epidemiological
''traffic light'' turns on, at 20 per 100,000 - warning yellow. The
second factor - the coefficient - is the so-called coronovirus
reproduction index, i.e. the number of people infected by one infected
person. Only when this coefficient is \textless{} 1.0 can the epidemic
be kept under control. If for 3 days in a row 1 infected person will
infect 1.1 healthy - the color of yellow is turned on, at a factor of
1.2 - red ''traffic light'', the third criterion - the number of beds
for heavy patients with COVID-19 in the intensive care and intensive
care units in the clinics. In the ''quiet period'' 9\% of the beds are
occupied, if this indicator reaches 15\% - yellow will light up, at 25\%
- red color of the epidemiological ''traffic light''
(\emph{http://p.dw.com/p/3cAza}).

With two yellow signals at 3 ''traffic lights'', the Berlin (Senate)
management begins a thorough analysis of the situation, and with two red
signals, it decides whether to introduce quarantine restrictions again,
if yes, which ones.

Obviously, apart from these figures, it is important to monitor the
dynamics of the epidemiological process.

German scientists have summed up the first results of the fight against
COVID-19 in the country (DW-Breaking World News, 20.05.2020) and among
the key factors to contain the coronavirus epidemic in Germany, they
call the decisive actions of the authorities, on the one hand, and the
loyalty of the population to the decisions of the authorities, on the
other. Now, after the easing of restrictive measures, in places of mass
appearance of people, such measures as thermometry in front of the
entrance to shops, mandatory hand disinfection, issuing masks to all
visitors and inside the building, social distance is maintained.

According to German scientists (prof. Karl Gustav Karus University
hospital Michael Albrecht) the new coronavirus has nothing to do with
ARVI or flu. COVID-19 in the worst case affects not only the lungs, but
also other internal organs, causes severe immunological reactions in
them, affects the central nervous system. Scientists believe that the
widely discussed problem of lack of ventilators is just one aspect of
the treatment of patients with COVID-19. Thanks to the cancellation of
public events and the prohibition of human contact, the spread of
infection in Germany was stopped (\emph{http://p.dw.com/p/3cAza}).

Similar experiences in the fight against the pandemic in Austria, the
Czech Republic, China, Russia have also shown the effectiveness of such
restrictive measures (morbidity, mortality, etc.).

According to various virologists from England and Germany, the pandemic
may last for another one to two years. It is believed that COVID-19, on
the one hand, will not disappear, and on the other, will not become an
obstacle to the normalization of life, which will occur due to
vaccination or the acquisition of immunity by the population naturally
{[}7{]}.

According to computer simulations of the pandemic from Johns Hopkins
University, which were developed under the condition that antiepidemic
measures were maintained or introduced, quarantine measures could be
withdrawn in most countries no earlier than August-September 2020.

The emergence of the experimental vaccine and its application to the
vaccination of medical personnel is predicted in November 2020, and mass
vaccination in spring 2021 {[}8{]}.

One of the most common models for predicting the development of
epidemics is SIR, which was developed in the late 1920s (an acronym
formed from the first letters of the words ''susceptible'', ''infected''
and ''recovered'') {[}15{]}.

The essence of the SIR model is that the entire population is divided
into the susceptible -- those who may be infected, those who are
actually infected and recovered.

Several variations of the models have been developed to date, including
SEIR, where E means exposed, i.e. infected with the virus during the
incubation period (contact). These people have already been infected,
but the symptoms of the disease are not yet apparent. According to the
SEIR model, susceptible people first become infected, then the
incubation period lasts for some time, after which they develop symptoms
and eventually recover or die. In the case of COVID-19, infected people
can infect others before symptoms appear, which makes the virus
particularly contagious (the incubation period of the coronavirus is on
average 5-6 days) {[}16{]}.

The infectivity (pathogenicity) of the virus is measured using the index
(coefficient) of basic reproduction -- RO, if it is equal to 1.0, then
each person infects another person, and that person then passes the
virus to another person, and so on.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Fig. 1 Distribution of infection with different indices of reproduction
(R). (Source: Imperial College London).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Fig. 2 Changes in the reproduction index (R) in the UK under various
restrictive measures. (Source: Imperial College London).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Fig. 3 Scenario of epidemic development in Russia without restrictive
measures. (Source: Covid-19-scenarios.org)

Increasing RO per unit significantly accelerates the process, if RO is
2, then the first infected person transmits the virus to two more
people, then each of them transmits the virus to two more people and so
on.

The index of the current COVID-19 coronavirus is about three. When the
authorities restrict people's contacts, the reproduction index
decreases. Now all countries are trying to lower the reproduction rate
below 1, hoping that at a slow rate of infection, restrictive measures
can be eased (Fig. 2).

Reducing the reproduction index does not yet mean defeating the virus,
but a low infection rate can be controlled through more economical
measures - wearing masks, mass testing, tracking contacts and timely
isolation of people with symptoms.

In order to model the coronavirus distribution, the University of Basel,
Switzerland, developed an interactive model based on SEIR, where data
(number of inhabitants, age structure, number of confirmed cases, etc.)
are loaded automatically and RO is assumed to be 2.64-3.23.

If no restrictive measures were taken in Russia, according to this
model, 1.3-1.36 million people would have died by the beginning of July,
and the number of infected people at the peak of the epidemic would have
been 14-22 million (Fig. 3).

If Russia eases the restrictions so that the number of people's contacts
will increase by 50\%, the number of new infections may increase to
300,000 by May 31, 2020, and if nothing is changed or the number of
contacts reduced by another 50\%, the increase in infection will be
almost invisible or not at all.

Based on mathematical modeling of COVID-19 epidemic development in
Moscow, 5 scenarios of epidemic suppression and their possible
consequences are presented {[}18{]}. The extended SEIR model {[}15{]},
implemented as a public computer program, was used for modeling. 5
scenarios of the epidemic development are considered: 0 - zero scenario
corresponds to the absence of protective measures, scenario A - a mild
step to suppress the epidemic (closure of schools, universities,
recommendations to elderly people not to leave home), scenario B and D -
a complete knockdown, introduced in scenario B from the beginning of
May, in scenario D - from the beginning of April 2020. In the O-variant,
the number of deaths from COVID-19 in Moscow will exceed 100 thousand
people, and the number of critical patients at the peak of the epidemic
will exceed the capacity of the healthcare system by more than 10 times.
Scenarios A and B do not radically reduce the number of deaths, and the
number of critical patients at the peak of the epidemic will continue to
far exceed the capacity of the health system. In addition, scenario B
assumes that the epidemic will last for more than a year. Scenarios B
and D can suppress the epidemic and significantly reduce the number of
deaths (by 30 and 400 times, respectively). At the same time, as a
result of these two scenarios, the population does not develop
collective (group) immunity and the population will remain susceptible
to repeated outbreaks of the epidemic.

Of the 50,000 Moscow citizens who voluntarily tested, antibodies to
COVID-19 were found in 12.5-14\% who are developing or have developed
immunity to the coronavirus. Rather, the examined patients suffered from
the disease in an asymptomatic or mild form, without contacting medical
professionals. Based on the results of these studies, it can be assumed
that those who acquired immunity during the asymptomatic course of
COVID-19 in Moscow may be from 1,586,000 to 1,776,000 people, and the
total number of infected, including officially registered (applied for
medical care) patients then is from 175,000 to 1,946,000 people.
Consequently, the proportion of those identified in medical
organizations is only 8.69-9.64\% of the total number of infected
people.

During the last month, the growth of COVID-19 cases has been gradually
decreasing: for example, during April 15-19, 2020, this figure was
14-15\%, May 1-5, 2020 - 7-8\%, and during the last week it dropped to
3\% (21.05.2020).

In Sweden, the pandemic strategy included the following measures: 1. Do
not interrupt business activities. 2. Don't disrupt people's daily
lives. 3. Systematically move towards achieving collective immunity.
Citizens were asked to observe social distancing precautions, but they
were not required to do so and were not penalized for non-compliance.
Two weeks ago, the health care system was on the verge of collapse, but
the situation has improved and there has been no collapse. The number of
infected people is still growing, and the death rate is higher than in
other Scandinavian countries, but lower than in countries that have
taken radical isolation measures. WHO now considers the Swedish model to
be a possible model for countries waiting for a vaccine.

The effectiveness of COVID-19 restrictive measures to prevent the spread
of infection has been studied comparatively in the states of Iowa (where
they were not introduced) and Illinois, where these measures were
introduced from March 21, 2020. {[}17{]}. In addition, the difference in
the timing of closure of schools and businesses, population density and
income levels were taken into account. The population density was higher
in Iowa (114.2 people per square mile) than in Illinois (78.2 people).
Summarized COVID-19 cases for 10,000 populations in both states were
compared prior to the State of Illinois self-imposed isolator ordinance.
After the decree, the incidence became higher in Iowa, decreased in
Illinois. Within 10, 20, and 30 days of the Illinois Home Isolation
Ordinance, the difference in COVID-19 cases was 0.51 per 10,000
residents (SE 0.09; 95\%, CI is from 0.69 to 0.32; p\textless{}0.001;
-1.15 per 10,000 population (SE 0.49; 95\% CI is from -2.12 to -0.18;
p=0.02) and -4.71 per 10,000 population (SE 1.99; 95\% CI is from -8.64
to -0.78; p=0.02), respectively. These data demonstrate the
effectiveness of home isolation to prevent the spread of COVID-19 even
in selected regions of the country.

Medical organizations are known to be one of the frequent outbreak
centers of infection. Often, when such a focal point arises in a general
hospital, infected patients are transferred to other hospitals, creating
a chain of infectious disease outbreaks, sometimes from infectious
disease hospitals to non-infectious disease hospitals for surgical
interventions. It is always a high risk of infection for patients and
medical staff. It seems reasonable to introduce a surgeon to infectious
diseases hospitals and to organize an operating room.

Conclusion. Analysis of the prevalence of the new coronavirus disease
COVID-19 over a 4-month period from the initial ''emotional'' assessment
based on intensive indicators is gradually moving to a system of
''medical statistics''. The actual epidemiological situation, trends and
prognosis can be most reliably assessed and determined based on relative
morbidity and mortality rates.

It is necessary to distinguish such indicators as ''morbidity'',
''infection rate'', ''mortality'' and ''lethality'' according to the
generally accepted postulates of medical statistics and epidemiology.
Proper calculation of such indicators as morbidity (number of patients
with COVID-19 per 1,000/100,000 of population), the rate of infection
(or reproduction), allows to objectively assess the effectiveness of
various restrictive measures in dynamics, helps to make decisions about
the continuation or weakening of these activities, and for the health
system - about the possibilities for the near future to cope with the
upcoming flow of patients or make adjustments to strengthen their
resources. Approximately the same importance of another indicator -
mortality (the number of deaths per 100,000 population), although it
characterizes the state, the level of health care system. Indicator -
lethality (\% deceased to the number of patients) - is primarily an
assessment of the activities of medical organizations, medical workers,
the level of medical knowledge, professionalism, the state of
implementation of research results. Undoubtedly, the level of lethality
is also connected with material and technical, medical equipment of
medical organizations, opportunities of conversion of medical
organizations into infectious diseases hospitals, organization of
intensive care and resuscitation departments, providing the latter with
equipment for non-invasive and invasive ventilation of the lungs,
hemodialysis, efferent methods of treatment.

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