Covid-19

SARS-CoV-2 virus illustrated

Intelligence is to choose the satisfactory, or the not too bad, among the naturally possible (adapted from Gottfried Wilhelm Leibniz and Herbert Alexander Simon)


This book is intended to identify the scientific questions, and the answers, important to the fight against the Covid-19 pandemic.

We need good knowledge, truths and proofs, to react intelligently and to calm down. The future is being prepared with today's thoughts.

The catastrophe[edit]

In a pandemic, each individual can be the cause of thousands of infections: he contaminates two or more others, which in turn contaminate twice as much, or more, and so on. Those who refuse protective measures, because they are not afraid of catching the disease, are sources of contamination for everyone else, real dangers for all of humanity.

Contaminated people are very contagious before the first symptoms appear [1]. This is why the isolation of sick people is not enough to contain the epidemic. The temperature reading at the airports was not enough. On the Charles de Gaulle aircraft carrier, the majority of sailors are contaminated despite the isolation of the sick.

If we do nothing, the pandemic can grow into exponential explosion (1,2,4,8,16,32,64,128,256,512,1024 ...), the hospitals are quickly overloaded and we no longer even have the means to treat the diseased, which increases mortality (dying by suffocation because the lungs no longer work...). If the epidemic explodes, many workers will no longer be able to work and we can fear the worst: no caregivers, no electricity, no running water, no food supply, no phone, no police, no garbage collection ...

If this epidemic explodes, almost 90% of the population could be contaminated, because this virus is so contagious that there is not enough time for people to be immunized.

One reason to hope is that this virus rarely kills not too old and healthy people, unless they are overweight[2]. The most vulnerable are the elderly (over 65), those with a medical history (diabetes...) and those who are overweight.

Infected people who are not very old and who are in good health most often (not always[3]) have less severe symptoms (cough and high fever for a few days, disorientation, exhaustion, loss of smell or taste...) or no symptoms at all.

The solutions[edit]

Two solutions:

  • Regain control of the epidemic to make it regress to a level where it is manageable. It seems that early detection and tracing of infected people can then prevent it from exploding again. However, precautionary measures are still to be recommended.
  • Let the epidemic explode for the not too old and healthy population while protecting the most vulnerable (if vulnerable people are not properly protected, it could be a genocide).

Regaining control has considerable economic and social cost: closing most businesses, stopping a lot of activities, depriving the poor of their livelihoods...

Letting the epidemic explode is a very dangerous solution. Many workers will fall ill at the same time. Hospitals will be overcrowded. It is not even known whether those who caught the disease will be properly immunized for a long time. The long-term consequences of the disease are unknown. The virus could mutate and become much more deadly...

In countries where regaining control seems impossible, it is better not to let the epidemic explode too fast, so that people are not all sick at the same time. So precautionary measures have to be recommended: hand washing, wearing a mask or scarf ...

How to regain control?[edit]

All possibilities of transmission must be avoided as much as possible, to bring down the transmission rate (the number of people infected by one already infected person) below 1, in order make the epidemic regress. With a transmission rate of 1/2, two infected persons infect one another person on average. The epidemic is extinguished by exponential decrease: 1, 1/2, 1/4, 1/8, 1/16 ...

As long as the epidemic has not been brought under control (only a few new cases per day), it must be regressed quickly, with safety instructions which make the transmission rate drop far below 1. When it is under control, we may relax the safety instructions, provided that the transmission rate does not exceed 1, otherwise the epidemic will explode again.

Here are few ways to slow down the Covid-19 transmissions:

  • Wash your hands frequently and thoroughly [4], especially when you go out (to protect others) and when you come back (to protect your home). Objection: does this really protect us from the virus? Answer: it's not enough protection. But this is sensible, reasonable advice, because dirty hands are generally transmitters of viruses, or other pathogens.
  • Restrain yourself from coughing and sneezing, or sneeze into your elbow if you can't help it, except when you are at home or very far from others, in an open space. Droplets ejected when coughing or sneezing are the main vectors of transmission of the virus.
  • Wear a mask or scarf in all places where there is a risk of contaminating others. Even those without symptoms can be very contagious [5]. A mask made with paper towels [6] is recommended, because its pores are smaller than those of a fabric.
  • Avoid touching eyes, nose and mouth [7], except after washing your hands thoroughly.
  • Do not talk to each other if you're too close [8] and wear a mask or scarf when speaking, unless you live in the same house or apartment. If you share the same house or apartment it seems very difficult to prevent the transmission of the virus.
  • Protect workers with plexiglass windows as much as possible.
  • Avoid going out of your house as much as you can, unless you stay away from others (2 meters if possible, 1 meter minimum).
  • Wear goggles or a ski mask.
  • No speaking on stairs or elevators, so as not to contaminate the whole building.

How to protect others? When you leave your house, wash your hands very carefully, wear a mask or scarf, refrain from coughing and keep your distance (2 meters if possible, 1 meter minimum).

How to protect yourself?

  • When you leave your house, you put on a mask made with two or three paper towels (a paper towel protects better than a piece of fabric, because its pores are smaller, two or three is better than one), a stapler and elastic bands. Here's how to do it: Fabriquer un masque de protection par le Pr Garin
  • You carefully fit it on the face with an elastic ribbon between the neck and the skull and a ski mask (remember that a gas mask protects only if it is very well put on. If it is badly put on, you die believing you are protected). Here is the result (This ski mask does not let see the gaze. It is a serious error because I look like a soldier of the Apocalypse. We speak by the gaze: politeness, respect, trust ...):
    How to protect oneself with paper towels, a ski mask and an elastic ribbon
  • You stay away from others (2 meters if possible, 1 meter minimum)
  • When you come home, you wash your hands very carefully, you throw the paper mask in the trash without touching its central part, you remove the ski mask without touching its surface, you clean or disinfect it, you change clothes and you wash them or you don't touch them for several days, you take off your shoes without touching the soles and you wash your hands again, you don't touch the products you just bought for several days, you leave them in a corner, you are careful not to touch your face unless you are sure that your hands are very clean, you disinfect surfaces (door handles, electrical switches ...) if you fear to have deposited the virus there, if you touch the ground you immediately wash your hands. You have to be careful not to let the virus enter your home, to be quiet.

Remember that in many countries the virus is almost everywhere.

What interaction distance should be recommended? 1 meter ? 2 meters ? More?

How far can the virus spread when we talk? [9]

How to make a mask with a plastic sheet
How to make a mask with a T-shirt

In the absence of surgical masks, is a simple scarf or an artisanal mask a protection to recommend?
Yes, because it prevents the spread of droplets. Artisanal masks (and even surgical masks) do not protect perfectly. There is always a risk of transmission. But the rate of transmission must be lowered below 1, to put an end to the epidemic. Even imperfect protection can, therefore, be very effective.

How to make our own masks? [10]

How should a cloth mask be washed? At 60°C (140°F) with ordinary detergent.

The diameter of the virus is approximately 1/10000 mm. To protect ourselves, should we reason about this very small length or the diameter of the saliva or mucus droplets that we exhale? Presumably, droplets are the most dangerous vectors of transmission. Therefore a simple scarf is effective protection.

What are the most dangerous droplets? Those that are transmitted face to face, those that stay long in the air or those that settle on surfaces?

Droplets can contaminate the eyes. Should we wear glasses? Ski goggles? A sheet of transparent plastic in front of the face? Wearing glasses may add a layer of protection [11].

How long is the virus dangerously lying on inert surfaces? Should we disinfect?
The virus can remain on inanimate surfaces up to 9 days [12].

How long can the virus dangerously floating in stagnant air? Should we be wary of confined atmospheres? Should we ventilate?
There is a possibility of transmission in a closed environment for a long-time exposure to high concentrations of aerosol [13].

Can the virus be transmitted through food and drink? Presumably yes, as soon as the food is contaminated with droplets.

How long do patients remain contagious after being cured?

A protocol to reopen stores and confined spaces (to be discussed): wash your hands systematically at the entrance and at the exit with hydroalcoholic gel, prohibition of coughing, wear a mask or scarf and ski goggles, respect a distance of two meters between customers, protect workers with a plexiglass window, pay with a contactless card or a smartphone ...

For obvious psychological reasons, family outings (or couples, or solitary) must be authorized, provided that the families remain distant from each other.

For obvious economic reasons, it is necessary to authorize the reopening of all stores, provided that the safety instructions (hand washing, safety distance, wearing of a mask or scarf ...) are respected.

How to interpret the official numbers?[edit]

Do the official numbers, which Johns Hopkins University [14] synthesizes, represent reality? How to interpret them? How are confirmed cases counted? How many tests are performed each day? Who are the people tested? How are the dead counted? What should we think of statistical aberrations?

One needs precise information on the methods of counting to reason correctly on these numbers. In the absence of precise information, these numbers are more like antiscience than science, because they do not give us the means to reason correctly and they can mislead us.

Why is this virus more contagious than the others?[edit]

Because of asymptomatic carriers? The duration of incubation? Persistence time on inert surfaces? Persistence in the air?

An hypothesis : infected people are very contagious before the first symptoms appear [15]. If this hypothesis is proven, to recommend to the population not to wear a mask or scarf when they are not sick is a serious error. It also explains why taking temperatures at airports was a completely ineffective measure.

What are the most dangerous places?[edit]

The hospitals, where they receive sick people, do their best to protect us from the virus: protective equipment, isolation of sick people, disinfection ...

It seems that the most contagious people are not even sick [16]. In supermarkets and public transport, protective measures are very weak. In France, most customers and employees do not even wear a mask. This could make supermarkets and public transportation the most dangerous places in the world, in all countries where the epidemic has spread widely.

Reducing the mortality rate[edit]

What are the factors that cause variation in the mortality from the virus? [17]

What mortality rate should be taken into account? 1/1000? 1/100? 1/5?

Is there an effective treatment to recommend when the first symptoms appear?

Isn't it a mistake to start treatment only when the symptoms are severe and the virus has already invaded the whole body?

Should we protect against the virus or against immune hyperresponsiveness? [18]

Does repeated and prolonged exposure to the virus increase mortality? As with any other poison, viruses are usually deadlier in larger amounts[19].

When we are sick and isolated, is it useful to adopt much stricter hygiene rules?

Are there eating habits to recommend? A balanced diet rich in vitamin C?

Should we recommend tobacco? [20] Is tar in the lungs or nicotine that protects smokers? (Reminder: in the long term, tobacco kills more than the virus)

Why does this virus spare children? Is it because they are more vaccinated? [21]

Containment or herd immunity?[edit]

Containment has dramatic psychological and economic consequences. Is it a cure worse than the disease?

In the absence of containment, the pandemic will explode. The consequences seem appalling. How many people will die? The death rate is unknown. If people can no longer be treated, should we count on a mortality rate of 1/1000 or 1/5? What about the survivors? Will they not suffer from irreparable consequences?

In poor countries, herd immunity seems to be the only hope. A vaccine will arrive far too late. Hospital resources are too limited to help the population. Containment is a remedy worse than the evil, because it can make people starve.

Does having caught the disease once and surviving protect us definitively against it? We do not know[22] [23].

For the survivors, are there irreparable consequences?[24] It seems so, at least in the most serious cases[25].

Is anosmia (loss of smell) irrevocable? No. Half of survivors recover from anosmia after two weeks. [26]

What should be done in poor countries?[edit]

The main advantage of containment measures is to prevent from the overloading of hospitals, so that the sick can be properly helped.

In poor countries, there are not enough hospitals, even in the absence of a pandemic. So it seems that containment is useless, except to kill people from hunger.

Protect the elderly and the sick. Do not approach them unless you are wearing a mask or scarf. Do not take their hand unless your hands are very clean.

Do your best to eat correctly, because malnutrition will make you weaker in front of the virus.

Where is the right path?[edit]

If we underestimate the severity of the illness (it's just a benign flu), we run the risk of causing millions of deaths and disabilities. If we overestimate it, we take the risk of proposing solutions that are worse than the disease. Where is the right path?

As this disease is new, there are few scientific answers. There are many more questions than reliable answers. Scientists need time to work and have hindsight.

Is confinement the cause of economic disaster?[edit]

Should we choose between confinement, which puts people out of work and drives businesses to bankruptcy, or deconfinement, which explodes the epidemic and can cause a genocide of the most vulnerable people?

If confinement condemns the poorest to starvation, it is obviously a remedy worse than the disease.

But to believe that confinement is the cause of the economic disaster is a serious error. The alternative between confinement which destroys jobs and deconfinement which would allow recovery is a false alternative.

Even without confinement, the economic crisis is very serious.

Several examples:

  • Even if tourist aviation is authorized, who today wants to be on a crowded plane to benefit from a week or two of vacation abroad? If the planes are not crowded, the airlines are not profitable.
  • Even if the opening of restaurants is authorized, who today wants to catch the virus to enjoy a good meal?
  • Can theaters and concert halls, discos, football stadiums ... still attract the public when everyone is afraid of the virus?
  • If the trains are crowded they spread the virus. If they are not crowded, they are not profitable.
  • Going shopping has become very anxiety-provoking. Even if we authorize the reopening of all shops, who will find pleasure in shopping?
  • Who today would agree to be in a crowded subway to go to work?

...

The problem is not confinement, the problem is the virus, which forces us to radically change the way we live, work and think.

As long as we do not adapt to this new reality, by dreaming of a rapid return to the previous life, by taking our desires for reality, we refrain from finding intelligent solutions to this catastrophe.

What must be done in the long term?[edit]

When can we hope to have a vaccine? 1 year? 3 years? 10 years? More?[27]

How should we organize work and other activities if this pandemic lasts for many years (or several decades)?

How can the economy start again without restarting the epidemic? Australia, China, South Korea, Switzerland and Austria seem to be examples worth considering.

What will kill the most? The virus or the fight against the virus?

The economic crisis could be more devastating than the virus itself.

The poorest may die from hunger. Is there any other solution than the distribution of free food ?

Economic activity depends on long-term expectations (It's the B-A BA of the science of finance). We need a long-term vision to organize the economic recovery.

An optimistic scenario:

In the coming months we find an effective treatment, which can be mass produced, and which is sufficiently harmless to be taken without going to the hospital. In this case, we can let the economy go without restrictions, in maybe six months.

A pessimistic scenario:
There is no effective treatment or vaccine in the years (or decades) to come (no effective HIV vaccine has been found despite more than 35 years of research). Even those who have already caught the virus are not properly immunized. In this case, we will never find our previous life and will have to respect safety instructions which oblige us to radically modify our ways of living and working.

In the coming months, the economic crisis will be the most serious in modern times: most planes are grounded or are unprofitable. Likewise for trains. The summer season will not be profitable for most tourism professionals. Cafes, restaurants, performance halls (concert, cinema, theater), major sporting events, will not be able to reopen or will rarely be profitable. Car sales are kept to a minimum. All companies working upstream are affected and risk bankruptcy. We can fear an unemployment rate higher than 50%. The comparison with the crisis of the 1930s is irrelevant because the causes are very different.

Should we ban all gatherings for years (or decades) as soon as they are too numerous?

Even if we all wear a mask, the spaces are very near one another are very dangerous.

Public transport is a very dangerous place when it is crowded.

What will become of performance halls, discos, cafes and restaurants, planes and trains, tourism, in the years (or decades) to come?

Some suggestions so that cafes and restaurants can reopen their rooms: space tables, order online for a fixed time, customers must keep their mask when they are served, limit customers (single people, couples, families ... ). Takeout is recommended.

It would be horribly unfair for individual entrepreneurs who went into debt to develop a now impossible activity that they collapse in debts. For the sake of justice, we must cancel their debts.

Those who have lost their job and have no hope of finding it again, because their activity is now impossible, must be helped and consider retraining.

When possible, all online activities should be recommended: e-work, e-school, e-shows and e-entertainment, e-business, e-politics, e-voting, e-medicine...

Theology[edit]

Neither God nor Christ nor Mohamed nor the Buddha stop the bullets, the hands of torturers and the viruses.

Viruses kill equally the good and the bad. Therefore a virus is not a divine punishment.

Could a mutation make the virus more dangerous?[edit]

In general, mutations make viruses less deadly. It is explained by natural selection. A very deadly virus spreads less easily than a mildly deadly virus, because once infected people are dead, they cannot spread the virus. But it seems that SARS-CoV-2 is very contagious before the first symptoms appear, so well before killing. A mutation which makes it more deadly would not therefore prevent it from spreading.

How many Covid-19 deaths are not counted as such?[edit]

An example: in Brazil, the number of deaths officially linked to Covid-19 is relatively low, much lower than the number of deaths in ordinary circumstances. Yet the undertakers are overwhelmed [28]. Should we not conclude that most of the Covid-19 deaths are not counted as such? [29]

Authority or freedom?[edit]

In mainland China, an authoritarian regime that bans free media and imprisons protesters, they have achieved remarkable success: being the first to reverse an epidemic of which they knew nothing at first. They succeeded thanks to their intelligence and their dedication to the general interest [30]. In the United States, which has the fundamental principle of respecting individual freedoms, it is an indescribable disorder. Does this mean that authoritarianism has won against freedom?

A few countries (Australia, Austria, Iceland, New Zealand, Norway, South Korea, Switzerland, Taiwan ...) have managed to reverse the epidemic with measures that more respect freedom. So it seems that we can find a fair middle.

How to live well?[edit]

All gatherings should be avoided as much as possible, unless a safety distance (2 meters if possible, 1 meter minimum) is respected.

We can allow walks in nature or public gardens (but not play areas for children), provided we can keep our distance (no crowded public transport, sidewalks or beaches).

To maintain social contacts, the telephone and the internet are the best solutions.

Sex is vital for most people. It is a mental health issue. Couples meetings must be authorized. Sex can transmit the virus (mainly through saliva, even if you don't kiss). Lovers need to know that they can get infected. But it is a mode of transmission that does not explode the epidemic, because the rate of transmission does not exceed 1.

How to reopen schools?[edit]

Let all the schoolchildren wear a mask and a visor. There is a health reason, because the virus can spread through the eyes. But there is above all a psychological reason: schoolchildren will spontaneously learn to respect safety instructions: don't touch my visor! It won't traumatize them, because with a visor you look like a cosmonaut. They will invent new games, as if they were cosmonauts, spontaneously respecting the safety rules.

Miscellaneous questions[edit]

What rules must be changed to adapt to this emergency situation? [31]

What is the proportion of asymptomatic people among those infected? 5%? 20%? 50%? 90%?

How to explain the successes of Australia, Austria, mainland China, Iceland, New Zealand, Norway, South Korea, Switzerland, Taiwan...?

Are asymptomatic people contagious?

Is wearing a mask a sufficient measure to reverse the epidemic?

Is the Vienna metro crowded? (In Austria, it seems that they are in control of the epidemic, despite the partial lifting of confinement, with the compulsory wearing of a mask in public transport and shops, and rules of social distancing.)

Is Africa really a relatively spared continent?

Should brandy above 70° be recommended to disinfect food?

Useful resources[edit]

Johns Hopkins University

Our World in Data

Health System Response Monitor

China's Fight Against COVID-19

Conseil scientifique COVID-19

References[edit]

  1. "Virological assessment of hospitalized patients with COVID-2019, Nature". https://www.nature.com/articles/s41586-020-2196-x. 
  2. "Obesity Linked to Severe Coronavirus Disease, Especially for Younger Patients, NYT". https://www.nytimes.com/2020/04/16/health/coronavirus-obesity-higher-risk.html. 
  3. "Those We’ve Lost. Hailey Herrera, 25, Dies; Therapy Student Focused on Families, NYT". https://www.nytimes.com/2020/04/15/nyregion/hailey-herrera-dead-coronavirus.html. 
  4. "Coronavirus disease (COVID-19) advice for the public, World Health Organization (WHO)". https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public. 
  5. "Virological assessment of hospitalized patients with COVID-2019, Nature". https://www.nature.com/articles/s41586-020-2196-x. 
  6. "Fabriquer un masque de protection par le Pr Garin". https://www.youtube.com/watch?time_continue=6&v=7Lg0jnJ3hEo&feature=emb_logo. 
  7. "Coronavirus disease (COVID-19) advice for the public, WHO". https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public. 
  8. "Surfaces? Sneezes? Sex? How the Coronavirus Can and Cannot Spread, New York Times (NYT)". https://www.nytimes.com/article/coronavirus-how-it-spreads.html. 
  9. "Stay 6 Feet Apart, We’re Told. But How Far Can Air Carry Coronavirus?, NYT". https://www.nytimes.com/2020/04/14/health/coronavirus-six-feet.html. 
  10. "Fabriquer un masque de protection par le Pr Garin". https://www.youtube.com/watch?time_continue=6&v=7Lg0jnJ3hEo&feature=emb_logo. 
  11. "Coronavirus Eye Safety, American Academy of Ophtalmology". https://www.aao.org/eye-health/tips-prevention/coronavirus-covid19-eye-infection-pinkeye. 
  12. "Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents, Journal of Hospital Infection". https://www.journalofhospitalinfection.com/article/S0195-6701(20)30046-3/fulltext. 
  13. "Diagnosis and Treatment Protocol for COVID-19: Etiological & Epidemiological Characteristics, Chinadaily". https://www.chinadaily.com.cn/a/202003/28/WS5e7e7e68a3101282172829e2.html. 
  14. "Johns Hopkins University". https://coronavirus.jhu.edu/map.html. 
  15. "Virological assessment of hospitalized patients with COVID-2019, Nature". https://www.nature.com/articles/s41586-020-2196-x. 
  16. "Virological assessment of hospitalized patients with COVID-2019, Nature". https://www.nature.com/articles/s41586-020-2196-x. 
  17. "A German Exception? Why the Country’s Coronavirus Death Rate Is Low, NYT". https://www.nytimes.com/2020/04/04/world/europe/germany-coronavirus-death-rate.html. 
  18. "Coronavirus : « Gardons-nous de tomber dans une réactivité maladive, viro-induite, sociale et politique », Le Monde (LM)". https://www.lemonde.fr/idees/article/2020/04/15/coronavirus-gardons-nous-de-tomber-dans-une-reactivite-maladive-viro-induite-sociale-et-politique_6036607_3232.html. 
  19. "These Coronavirus Exposures Might Be the Most Dangerous, NYT". https://www.nytimes.com/2020/04/01/opinion/coronavirus-viral-dose.html. 
  20. "Coronavirus : la proportion de fumeurs parmi les personnes atteintes du Covid-19 est faible (LM)". https://www.lemonde.fr/planete/article/2020/04/22/coronavirus-une-proportion-reduite-de-fumeurs-parmi-les-malades_6037365_3244.html. 
  21. "Can an Old Vaccine Stop the New Coronavirus?, NYT". https://www.nytimes.com/2020/04/03/health/coronavirus-bcg-vaccine.html. 
  22. "Please, Don’t Intentionally Infect Yourself. Signed, an Epidemiologist., NYT". https://www.nytimes.com/2020/04/08/opinion/coronavirus-parties-herd-immunity.html. 
  23. "Who Is Immune to the Coronavirus?, NYT". https://www.nytimes.com/2020/04/13/opinion/coronavirus-immunity.html. 
  24. "We Need to Talk About What Coronavirus Recoveries Look Like, NYT". https://www.nytimes.com/2020/04/13/opinion/coronavirus-recovery.html. 
  25. "Please, Don’t Intentionally Infect Yourself. Signed, an Epidemiologist., NYT". https://www.nytimes.com/2020/04/08/opinion/coronavirus-parties-herd-immunity.html. 
  26. "Coronavirus : l’altération de l’odorat et du goût est un marqueur important du Covid-19, selon une étude, LM". https://www.lemonde.fr/sciences/article/2020/04/07/l-alteration-de-l-odorat-et-du-gout-sont-des-marqueurs-importants-du-covid-19-selon-une-etude_6035891_1650684.html. 
  27. "How Long Will a Vaccine Really Take?, NYT)". https://www.nytimes.com/interactive/2020/04/30/opinion/coronavirus-covid-vaccine.html. 
  28. "Coronavirus : au Brésil, « nous sommes à la limite de la barbarie », LM". https://www.lemonde.fr/international/article/2020/04/24/coronavirus-au-bresil-nous-sommes-a-la-limite-de-la-barbarie_6037594_3210.html. 
  29. "Tracking the True Toll of the Coronavirus Outbreak, NYT". https://www.nytimes.com/interactive/2020/04/21/world/coronavirus-missing-deaths.html. 
  30. "China's Fight Against COVID-19". http://global.chinadaily.com.cn/a/202004/22/WS5e9e4802a3105d50a3d17964.html. 
  31. "An Outdated Law in Florida Is Preventing Me From Saving Lives, NYT". https://www.nytimes.com/2020/04/04/opinion/physician-assistants-hospitals-coronavirus.html.