Consequences of a venomous snake bite. The most dangerous zootoxins for humans: viper venom

Contrary to popular belief, snakes are not at all aggressive. Poison serves them for hunting and protection, so they try to spend it sparingly. When meeting with a person, it will try to stay away, the bite will follow only if the snake decides that it is in danger.

The composition of the poison includes necrotizing, hemocoagulating, hemorrhagic substances, as well as neurotropic cytotoxins in high concentrations. But the dose of poison when bitten is usually quite small, so they are rarely lethal, unless the bite fell on the face or neck.

Viper bite danger

For healthy person a viper bite often goes away without any consequences, especially with timely assistance. Sometimes a small dark spot may remain at the site of the bite due to partial necrosis of the skin. A more severe possible consequence is visual impairment.

The danger of a viper bite depends on factors such as the size of the snake, the weight of the victim and the state of his health, the bite site, the literacy of first aid and the amount of venom released.

The viper spends its poison sparingly, trying to keep its supply with itself whenever possible. Some bites may be harmless at all.

However, any snake bite should be taken seriously, as it is impossible to outward signs determine the amount of poison in the body.

Consequences of a viper bite

At the first moment after the bite, the victim feels only pain and notices two small punctures on the body from the teeth of the snake. After a short period of time, swelling appears, the skin becomes purple or cyanotic. Later, symptoms such as headache weakness, nausea, vomiting, shortness of breath.

In a person with cardiovascular disease, a snake bite can cause the development of a state of shock, increased heart rate, which in turn will accelerate the spread of poison and can be dangerous to the patient's health.

First aid for viper bite

The victim must be given complete rest to slow down the absorption of the poison. If possible, while waiting for help, the person should be laid on their side, wrapped warmly and given plenty of fluids.

Alcohol, tea or coffee should not be given as a drink, as they increase the heartbeat and contribute to the absorption of the poison.

A clean, dry bandage should be applied to the bite site. The wound can be pre-treated with hydrogen peroxide, if it is available. In any case, the victim must be taken to the nearest medical facility as soon as possible.

Snakes rarely evoke positive emotions: a reptile with an unblinking gaze and all that. Many, when they see a viper, experience simply wild fear. Crazy horror.

The explanation is simple - the fear for one's own life is inherent in a person by nature itself at the gene level. I myself am afraid of poisonous snakes in earnest. However, is it all that scary?

Few people know that the viper is a fairly peaceful reptile. When a person appears, the only thing she tries to do is hide and thereby save her life. The bite of a viper, as a manifestation of aggression, is an extreme protective measure. We will talk about the consequences of a viper bite and first aid a little later. Let's take a closer look at this snake first.

Viper bites are not uncommon in areas where they are common. The common viper, steppe viper and Pallas muzzle live on the territory of Russia.

Viper venom has the ability to increase the permeability of the vascular wall (hemorrhages appear), causes blood clotting and tissue death in the bite area. Deaths account for less than 1% of those bitten and are mainly associated with delayed first aid or improper use of antivenom for viper bites. It is dangerous if the bite fell on the neck and head, small children, the elderly or patients with chronic diseases suffered.

The viper, like many poisonous snakes, is characterized by a triangular shape of the head, noticeably expanded towards the back of the head, a short, snub-nosed muzzle, as it were, and a vertical incision of the pupil. The head is covered with many small multi-colored scales, often forming a pattern in the shape of the letter V. The tail is shorter, thicker and passes to the body with a sharper drop, especially in females.

The head of the snake is oval, covered, like in lizards, with large scales, the muzzle is elongated, the pupil is rounded; the tail is thin and long. On the back of the head there are usually light (to orange), but in some species there are dark spots, sometimes merging on the neck into a “necklace”. Excluding these signs common to snakes, the pattern of the body of some of them is indistinguishable from the color of the viper, which is also very diverse.

The main active components of viper venom are high-molecular proteases of hemorrhagic, hemocoagulative and necrotizing action and low-molecular neurotropic cytotoxins, although in smaller quantities than in cobra venom. After a viper bite, hemorrhagic edema, necrosis and hemorrhagic impregnation of tissues in the area of ​​​​venom injection occur quite quickly, accompanied by dizziness, lethargy, headache, nausea, and shortness of breath. In the future, progressive shock of complex genesis, acute anemia, intravascular coagulation, and increased capillary permeability develop. In severe cases, dystrophic changes occur in the liver and kidneys.

At the site of the viper's bite, two point wounds from the snake's poisonous teeth are visible. The bite causes severe increasing pain. Already in the first minutes there is hyperemia of the bitten part of the body (excessive filling of blood vessels). Edema spreads upward from the bite site. When poison enters the bloodstream, a general reaction can develop immediately or half an hour or an hour after the bite. Most of the time this happens within 15-20 minutes. There is dizziness, lethargy, headache, nausea, sometimes vomiting, shortness of breath, frequent pulse. Poison common viper according to the mechanism of toxic action, it is a poison of predominantly hemorrhagic (causing hemorrhage), blood clotting and local edematous-necrotic action. The closer the bite is to the head, the more dangerous it is. In spring, viper venom is more toxic than in summer.

The poison released by the viper affects human body hemolytic action. After a bite, a painful edema with multiple small hemorrhages is observed in the affected area. In addition, vascular thrombosis and hemorrhage of internal organs may appear. The bite site is marked by two deep wounds left by the snake's poisonous teeth, the blood in which is quickly baked, preventing further bleeding. The tissues surrounding the wound, as a rule, turn blue and swell. With the defeat of the hands, after a while, the fingers may stop bending, this is due to the soreness of the edema, which extends to the very elbow.

The victim may experience nausea, chills, and fever. In some cases, there is a deterioration in cardiac function, dizziness and severe vomiting occur. This is due to the extensive damage circulatory system, which is accompanied by a sharp decrease blood pressure and internal blood loss, which leads to general weakness and even loss of consciousness. AT severe cases seizures and increased arousal may occur. The result of such complications can be fatal, which occurs, as a rule, in half an hour, although sometimes death of the victim is possible after a day or more.

Factors affecting the severity of the consequences of a snakebite.

Several factors influence the severity of the consequences of a snakebite.

· Age, body size and health status of the patient. Intoxication in children is usually severe and death is more likely in them, since a relatively large dose of poison falls on the body of the victim with a smaller size.

· Bite site. Bites to a limb or adipose tissue are less dangerous than bites to the trunk, face, or directly to any blood vessel. A direct hit by poisonous teeth is more dangerous than scratches, glancing blows, or blows to bone. The exit hole for the expiration of poison in the snake's poisonous tooth is much higher than its top; thus, the tip of the poisonous tooth can penetrate the skin without causing intoxication; even a thin layer of clothing can provide serious protection. Due to the fact that the wound from a snake bite is superficial, about 20% of patients bitten by poisonous snakes will not develop intoxication, even if poisonous teeth penetrate the skin.

· snake size(a large pit viper is capable of injecting more than 1000 mg of poison into its prey, which is six times the lethal dose for an adult); the degree of irritation or fear experienced by the snake (if the snake is hurt, it can inject more poison); the condition of the venom teeth (broken or recently replaced) and the condition of the venom glands (recently emptied or full). All of these factors are important.

Contrary to popular belief, the bite of a snake that has recently killed an animal and is well fed is not necessarily less poisonous to humans; a snake usually does not fully expend its venom during a single bite.

· The presence of various bacteria, especially clostridium and other anaerobic microorganisms, in the snake's mouth or on the skin of its prey. This can lead to severe infection in the necrotic tissue at the site of the bite.

· Exercise stress or effort - such as running, immediately after the bite. This accelerates the systemic absorption of the poison.

In most cases, you can protect yourself from the bite of a viper and any other snake by observing the basic rules of behavior in potentially dangerous places:

1. If you are not specialized in snake trapping and don't understand snake types, it's better not to touch them and don't let children play with them.

2. In areas where snakes live, wear sturdy, high-top shoes.

3. Stay vigilant in thick grass, overgrown pits. Before you set foot there, check for vipers lurking there.

4. Never chase a snake.

5. When picking mushrooms or berries, feel the grass around them with a stick. This will allow the viper to crawl away and at least reveal itself with a hiss.

6. If you see a snake crawling, do not move until it crawls away.

7. If the snake has taken a threatening posture, slowly step back without making sudden movements. Do not put your hands forward in defense. Don't turn your back to the snake. If you have a stick, hold it in front of you towards the snake. Do not run from the snake you meet, you can step on another, unnoticed before.

8. Use a flashlight at night as some snakes are especially active on warm summer nights.

9. Destroy rodents in time in your homes, outbuildings, household plots, since mice and rats are very attractive to snakes.

10. If you live in areas where venomous snakes live, as a preventative measure, coat your doorstep with mustard every day. Snakes are very sensitive to it and, as a rule, do not crawl over objects treated with it.

11. Do not settle down for the night near trees with hollows, near rotten stumps, caves, garbage heaps. In steppe conditions, carefully inspect the bed or sleeping bag before going to bed. If you see a snake in bed in the morning, don't panic, don't make sudden movements that might provoke it to attack. Better call for help and wait for the snake to crawl away on its own. With some skill, you can try to throw off a snake that is on a blanket or sleeping bag with a sudden sharp movement, while not forgetting about your tent neighbors.

First aid.

When bitten by a viper, you should immediately seek medical help. On the way to a medical facility, it is very important to keep the bitten part of the body immobile. The limb can be fixed with an ordinary scarf, sticks.

If there is no hope for medical assistance in the near future, then:

1. Move the casualty to a comfortable and protected area. Lay it so that the head is lower than the level of the body, which will reduce the severity of possible cerebrovascular accidents. Give the victim complete rest.
2. Using pressure movements, open the wound and begin to actively suck out the poison with your mouth, massaging the bite area towards the wounds. Intensive suction during the first 5-7 minutes allows you to remove up to 40% of the poison, while after 15-30 minutes this figure decreases to 10%. If the hand is bitten, the victim himself can suck out the poison.
3. When sucking, bloody liquid should be spit out periodically, and at the end of the procedure, it is necessary to rinse the mouth with potassium permanganate or plain water. It should be noted that in the presence of wounds in the oral cavity or dental caries, it is strictly forbidden to suck out the poison by mouth.
4. When the first signs of edema appear, stop sucking, and treat the bitten place with antiseptics. The use of brilliant green is not recommended, which will complicate the examination of the wound by the doctor.
5. Apply a sterile bandage to the damaged area, loosen it as swelling develops to avoid cutting into soft tissues.
6. To slow the spread of poison in the body, minimize the mobility of the affected body part. If the hand is bitten, bend it and fix it in that position. You can put on a tire.
7. To normalize the water-salt balance and remove the poison from the body, provide the victim with plenty of fluids. Give him plenty of broth or water.
8. If possible, give the victim 2-3 tablets of an antihistamine.
9. Do everything in your power to get the viper bite victim to the nearest medical facility as quickly as possible. With absence Vehicle transport the victim on a stretcher.

Many consider the introduction of a special serum to be a panacea for a viper bite. It can be bought at a pharmacy before a trip out of town. However, doctors do not recommend doing this, since this drug requires special storage conditions, and its shelf life is very limited. In addition, in most cases, you can get by with more gentle means.

What You Should Never Do (!)

You can not give alcohol, tea, coffee, as stimulating the work of the heart, but you need water, in order to avoid dehydration of the body. Previously prescribed corticotherapy and heparin (for local application) do not interfere with the development of edema and necrosis! It is also not recommended to apply a tourniquet as disrupting normal blood flow, which can cause irreversible consequences. Never instruct anyone to administer serum or other drugs outside of a medical facility - the medicine can cause more harm than a bite.

The antidote for a viper bite is a specific serum. It's called like this: Serum against the venom of the common viper. It is produced in biofactories, based on horse serum. The antibodies contained in it neutralize the venom of the common viper. The drug is a clear liquid in a glass ampoule. The volume depends on the activity of the drug in each batch, but not more than 3 ml. There are also foreign analogues of the drug.

Any survivalist clearly knows if his a viper will bite. But it’s one thing to know theoretically, and quite another to feel it all in your own skin. What, in fact, happened to the author of this photo report. Further - exclusively his own words, opinions and impressions.

Viper bite. Chronology and consequences (photo report)

We will describe how everything was by the hour, then by dates and with photos.

The bite itself is not very painful, for me the wasp bites more painfully. Blood flowed from the wound for about 10 minutes. The poison sucked as much as it could while the wound was open.

15 minutes after being bitten by a viper

After 5 minutes, I felt that my forearm began to go numb and hurt a little, then my shoulder, then my second shoulder. For all 15 minutes. Then the second shoulder let go.
I felt a little dizzy, but I attributed it to excitement, it went away in just a minute.
After half an hour, the brush began to noticeably swell in bite site. Removed all rings and bracelets. Another half an hour and I would have had to cut it off.

+45 minutes from being bitten

An hour later, the hand swelled up completely and the tumor went higher on the forearm.

1 hour 20 minutes after being bitten by a viper

The head “leads” a little, but not critical.

+2 hours

Volokolamsk, Central District Hospital - injected prednisone intramuscularly 2 ampoules (2 ml). They don't have anything else for that. They offered to go to the hospital with them. Refused. I could only sign the refusal with a cross 🙂 I couldn’t hold the pen - my fingers don’t bend as they should.

We're going to Moscow. The head is slightly spinning, if you do not spin and do not get on the bumps, it is quite normal to rulitsya.

+4 hours from viper bite

Emergency clinic in Moscow ~ 4 hours after the bite. The hand turns blue slowly. An ambulance was called from the emergency room, which took him to the Toxicological Department of the sklifa. On the way, they dripped one dropper.

About the Department of Acute Poisoning for the Mentally Ill (this is where all adults with snake bites in Moscow) one thing can be said - it is the only one in all of Moscow, and it is there that everyone gets with a squirrel and overdoses. So it's not boring for sure. Everything is taken away upon admission. The phone cannot be used. If you had any valuable things - they are handed over for collection under the inventory. At the checkout, everything was returned to me to the penny. But those who get here in an unconscious state, as a rule, are very surprised by the lack of money, keys, etc.

They immediately rolled in 3 more droppers, antibiotics, and, apparently, serum. By morning, the swelling began to subside, leaving in its place bruises along the veins and in places where there are more muscles.

A day after the bite of a viper

By the end of the second day, the edema subsided completely, there was a bruise on the entire right arm. compress something right hand almost impossible.

+1 day. There was a bruise at night

She was released from the hospital on the third day. Next to him lay a man with a bite in his leg. He had been here for a week and he was left to be treated further. viper venom had such a powerful effect on his body that the skin on his leg burst from the tumor.

Discharged with adventure. They didn’t bring my things, but since I was bitten, not a drug addict, and entered in clothes, which is actually a rarity in this department, they sent me to another building with a note)

Home because of the wild heat, I walked in a T-shirt. Epic: T-shirt, tights and a hand pierced with needles. The doctors said that " nothing, everything will be OK - you have an extract from us with you, show it to the PPSniks". Given where the extract is from, the statement is controversial.

On the third day, in the evening, I got sick serum injection site. As the surgeon said in the clinic in the morning, this is normal and for a long time. I was not mistaken ... It hurt for about a week.

Home treatment was prescribed as follows:

• Liaton ointment - on the whole arm if possible (I smeared before going to bed);
• Aspirin ass - according to the instructions.

+3 days

The whole arm is one big bruise. Not that say hello, hold something hurt.

+5 days

+8 days

New hematomas appeared.

12 days after being bitten by a viper

By this time I could already write with a pen, but it still hurt to shake hands. The expander was able to compress only after two weeks. Full recovery of the hand took about 3 weeks.

As you can see, even if you immediately sucked the poison out of the wound as much as possible, you will have to consult a doctor anyway. And then it takes a long time to get back to normal. So be careful, colleagues. Much easier viper bite rather than deal with its consequences.

The viper is a very peaceful snake, it attacks a person very rarely, only in case of danger. Usually vipers try to avoid people, so it is quite difficult to provoke its aggression: you need to either step on it with your foot or grab it with your hands. However, do not forget that this snake is very poisonous. The bite of a viper, although not fatal, is, admittedly, quite painful. Usually, after a bite, people recover after 3-4 days.

Over the past few decades, people have practically not died from a viper bite, however, deaths have occurred with improper treatment. A person meets with a viper quite often, but such meetings end in death in extremely rare cases.

For most adults, a viper bite does not threaten any serious consequences, however, the bite should not be taken lightly and first aid should be provided to the bitten immediately. In some cases, at the site of the bite there may be a dark spot- this is a consequence of necrosis of a part of the human skin. Rarely enough, but still there are complications associated with visual impairment.

The degree of danger of a viper bite is determined depending on the size of the bitten snake, the height and weight of the bitten, the state of health of the victim, where the bite was made, how quickly and correctly the first aid was provided, how much poison the snake released.

Vipers try not to excrete poison without urgent need, treat it carefully and economically. In some cases, when bitten by a viper, it may not emit poison at all, however, absolutely any snake bite must be taken very seriously, because it is not possible to determine externally whether the viper has emitted poison.

In our country, only the common viper is found. The bite of such a snake almost never leads to death.

First aid for viper bite

At any hospital, clinic or paramedical station there is a drug "Anti-Viper", designed specifically to neutralize the action and complete elimination from the body snake venom. However, when taking this serum, it should be borne in mind that improvements will be observed no earlier than after a few hours. It is highly desirable to spend this time under the supervision of a doctor, who is likely to be able to select other effective drugs to treat the effects of a viper bite.

The doctor usually apply iodine to the affected area, closes the wound with a bandage to prevent re-infection. The adoption of these measures, and especially the timely provision of first aid, with a high degree of probability will ensure a complete recovery in a few days, subject to bed rest and unconditional adherence to all the instructions of doctors.

It is unlikely that a viper bite will end for a healthy person lethal outcome, but prompt and competent treatment is necessary. If a person neglects his own health and does not go to a clinic or hospital, serious complications are possible, such as kidney failure. chronic form for the rest of my life.

What are the consequences of a viper bite for a person? How to provide first aid to the victim? What should be the treatment? You will find answers to these questions in the article.

general information

All representatives of the viper family are classified as poisonous snakes. Appearance quite remarkable, although it is quite often confused with the snake. The color of this snake varies from black to brownish-gray. They live throughout Africa, Asia and Europe. In Russia, this species is found everywhere, the only exception is Siberia. Here, scientists have identified about six types of common viper, Caucasian, Horned, Steppe and others are common. The common viper, the consequences of the bite of which we will consider, is small in size, and the body length rarely reaches sixty centimeters.

Description

The viper can be easily identified by the dark stripe that runs along the entire ridge. Unlike snakes, in which the head is round, in vipers it is triangular, while on the crown there is a pattern in the form of the letter X. Such snakes live for about fifteen years, preferring to live in one place. Vipers love damp and warm places. Old rat holes, cracks in the rocks are often chosen for the nest. Forcing her to leave her usual place can be forced by human intervention or hunger.

Like other cold-blooded creatures, vipers love warmth. They go out in search of prey at night, hunting lizards, rodents, small birds, but during the day they sit in a nest or bask in the sun. In winter, the animal hibernates, and awakening occurs at the beginning of spring, when there is still snow. AT middle lane Russian Federation the wintering period takes about two hundred days, in the north 215. The males are the first to leave the shelter.

When is the danger?

Vipers feel great at a body temperature of nine to thirty degrees. If these indicators fall below or rise above these marks, the animal dies. That is why snakes have to hide in a shelter all day and crawl out only a few times a day to warm up. People often encounter them in the forest due to their own inattention, receiving a poisonous bite. A person is not considered by this snake as a potential victim, they are afraid and do everything not to collide with him, and when they meet, they will never attack first.

A bite can only be obtained with a direct threat, if you step on a snake or pick it up. Before attacking, the snake will make a loud hissing sound. One more distinctive feature vipers is a bad hearing. They are not able to determine the approach of people by their steps, but are guided only by the tremors of the soil. In the case when the ground is too soft, the snake until the last moment is not able to catch the presence of an outsider.

Every year, doctors record several thousand cases. At the same time, no deaths have been noted so far, but this does not mean that snake venom is harmless. The consequences of bites are severe, this is often observed in patients with allergic reactions.

What does a bite look like

After an unpleasant encounter with a snake, in the first minutes only two red dots will be visible on the affected area - marks left by the teeth. Since the poison has a strong hemolytic effect, which leads to an acceleration and increase in blood clotting, the wounds heal quickly enough. The blood is baked, and a red spot appears around. After a short period of time, swelling appears in the affected area, causing significant pain and spreading quickly enough, the skin begins to swell and becomes bluish in color. If the bite fell on a limb, then a person can observe numbness of the fingers. In the most deplorable situations, after bites, vascular thrombosis is observed, as well as hemorrhage of internal organs.

What does the risk depend on?

The consequences of a bite from a common viper will depend on the following points:

• Snake volumes. It was found that the more cold-blooded, the more glands that secrete poison, respectively, its volume also increases.
• Height and weight of a person. The larger the bitten creature, the less impact the poison will have.
• Affected area. It is generally accepted that bites in the shoulders, neck, chest are extremely dangerous.
• General condition of the body. If there are problems with the heart, then there is the possibility of developing a state of shock.

Symptoms

It is extremely important to understand what the signs of a bite are in order to provide assistance in time if necessary. The first signal is severe pain at the site of the bite. Also, this area begins to swell, and the size of the limb can increase several times. The poison, which spreads through the bloodstream, causes hemorrhage, which causes a sharp decrease in blood pressure, swollen lymph nodes. Common symptoms are urge to vomit, nausea, heat, migraine, general weakness.

Bite for an adult and a child - consequences

What are the consequences after a viper bite? First of all, it all depends on the composition of the poison. The thing is that it is mostly considered hemo- and cytotoxic. This suggests that as a result of its impact, the body undergoes a deep functional and structural change in blood tissues or tissues, which leads to death. This effect is due to the composition of the poison, or rather a large number of necrotizing enzymes. At the same time, no neurotoxins are observed in viper venom, and due to this, its effect on nervous system not visible. And the production of poison by this representative is not as critical as, for example, a pit-headed snake or asps.

Despite this, for people who have suffered a viper bite, the consequences can be quite sad. This is especially true for those who have problems with cardiovascular system, or first aid was performed incorrectly.

For a child, a viper bite has serious consequences. It can lead to a decrease in pressure, internal blood loss, general weakness and loss of consciousness. In difficult cases, convulsions and increased arousal are observed. Such complications can lead to the death of the child.

Photos of the consequences of a viper bite for a person are quite frightening, therefore, for aesthetic reasons, we did not post them in the article.

dry bites

Perhaps the main role in the severity of the consequences of a meeting with an ordinary or steppe viper is given to the amount of poison that it emits. This is directly related to the hunting habits of the amphibian. Vipers hunt only small prey, doing it quickly, from cover, after which they wait for the poison to take effect. It is also worth noting that the poison is spent very carefully, the snake tries to always have a small amount in stock. That is why in some cases the bite of a steppe viper may not have consequences. It may be completely harmless.

Emergency help

The first and most reliable help for bites is a special drug that should be present in every clinic. This antidote is prepared on the basis of snake venom. But, as often happens, the victims of the attack are people who go to rest in nature, who do not have the opportunity to immediately go to the doctors. In addition, the serum must be administered intravenously, so not everyone will be able to carry out such treatment under the conditions of the campaign, even if the antidote is at hand. It is in such situations that you need to know how to provide first aid. Here the count is for minutes, but it often happens that after bites people get lost and do not understand how to act.

First you need to weaken the effects of the poison and call an ambulance. Before the arrival of the doctors, you should not be inactive, we carry out the following manipulations:

• The victim should be taken to a safe place and laid on the ground. Complete rest is extremely important for the patient, he should worry less and move around. This will help stop the rapid spread of the poison.
• The wound must be opened. To do this, fingers are pressed on its edges, and poison is sucked and spit out of it for ten minutes by mouth.
• Another condition is to ensure that you drink plenty of water (keep in mind that alcohol is prohibited). Water removes a small amount of toxins. There are some activities that are prohibited. You can not try to cut or cauterize the wound with anything, cover it with earth or pull everything with a tourniquet.

It copes well with weakness, eliminates residual signs of a bath diluted with milk, or a steam bath. To reduce pain and relieve redness of the wound, juice extracted from plantain or horse sorrel root is applied to the affected area. In the role of another natural antidote, for severe wounds, you can use boiled vinegar, a tincture made from the roots of elecampane, St. John's wort or ginger. Extremely high quality remove the effects of spicy products.

Conclusion

So, if you are a fan of going to the forest for mushrooms or berries, then you have probably come across this snake more than once. A meeting with a person usually ends tragically for a viper, because for many, killing a snake is a real feat. If you met with this animal, you should not commit rash acts, just give her the opportunity to move away. The snake bites only in the most hopeless situations. When the viper hisses, do not make sudden movements. Such actions do not mean that she will rush at a person. Quite the contrary: the bite will occur silently only when there is no other option, or a person accidentally steps on it.