infectious diseases

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An infectious disease is a disease in which a pathogen (i.e., a small organism that causes a disease) invades the body and causes symptoms. It's called Pathogens are classified according to their size and structure as bacteria, viruses, fungi, and parasites. When a pathogen invades the body, symptoms may or may not appear. Whether a person becomes infected or not depends on the balance between the infectious power of the pathogen and the body's resistance to the disease.

Bacteria, viruses and other pathogens do not cause problems when they are simply present on the outside of the body. This is called "colonization". In contrast, when a pathogen enters the body and multiplies in a specific organ or throughout the body, it is called an infection. When a pathogen invades the body and multiplies in certain organs or throughout the body, it is called an "infection". It is called "viral upper respiratory tract infection".

If a virus causes infection in the upper respiratory tract (nose and throat), it is called "viral upper respiratory tract infection" and if a bacterium causes infection in the lungs, it is called "bacterial pneumonia".

Pneumonia and other infectious diseases caused by a new type of coronavirus (SARS-CoV-2) that infects people are collectively referred to as It is called the new coronavirus disease (CoronaVirus Disease-2019: COVID-19).

Comparison of the size of viruses (Viruses), bacteria (Bacteria) and fungi (Fungus)

What is a bacterium?

The so-called "germs" are tiny organisms that cannot be seen by the eye. They are called unicellular organisms because they have only one cell. Bacteria can replicate and grow the same bacteria as themselves as long as they have a source of nutrients. 

Bacteria are also originally found on the skin, in the nose, throat and intestines. These are called "skin commensal bacteria" or "intestinal flora" and are normal rather than the cause of disease. It is said to help maintain the condition of the intestines. It looks like the bacteria in the gut are inside the body, but in reality, the "inside of the gut" = the center of the body. Since they are on the "opposite side of the body", we can say that they are on the "outside" of the body.

Bacteria that can cause disease in humans include E. coli, Staphylococcus aureus, and Mycobacterium tuberculosis. The first thing you need to do is to take an antimicrobial medication. Antimicrobial drugs (antibiotics and antibiotics) are used to target and kill the growth mechanisms of bacteria. Bacteria for which antimicrobial drugs are ineffective or have become ineffective are called drug-resistant bacteria. When antibacterial drugs that used to work, not only does it become difficult to treat the infection, but it also makes it more difficult to perform surgery It makes it difficult to provide a variety of medical care, such as preventing infections when the immune system is weakened by anticancer drug treatment or when

What is a virus?

They are about 1/10 to 1/50th the size of bacteria, very small, and do not have cells of their own (DNA and RNA are present). They do not have a mechanism to grow on their own (DNA and RNA exist), and by definition, they do not have It is not an organism. Viruses don't have cells, so they use the mechanisms in the host's cells to multiply on their own. It gets into other cells and lives on. When a virus invades the human body, it enters a human cell and makes a copy of itself, causing the cell to rupture In this way, the virus multiplies and enters other cells. In this way, the viruses multiply.

Viruses that can cause disease in humans include the influenza virus, noroviruses Known. The common cold (the common cold) is caused by a variety of viruses.

Viruses are different in size and mechanism from bacteria, so antibacterial drugs (antibiotics and antibiotics) do not work. Only a few antiviral drugs have been developed.

Various modes of transmission

The route of entry of a pathogen into the body is called the "route of infection" and can be broadly divided into vertical and horizontal infections.

Vertical infections are classified as placental infection, transplacental infection, transabortive infection, and mother-to-child infection. The term "horizontal infection" refers to anything other than a vertical infection. Horizontal infections are those that are not vertical infections and can be classified as oral, blood, contact, sexual, or There are droplet, air, and animal infections, and those that are important in general life are "contact infections They are "droplet and airborne" infections.

The new coronaviruses are said to be mainly droplet and contact infections, so these are called "droplet infection" and "airborne infection. Measures must be taken. In addition, because new coronaviruses are isolated from airway secretions and feces, the key to countermeasures is There are two points as follows

1) Preventing virus-containing droplets from attaching to the mucous membranes of the eyes, nose and mouth.

(2) Prevent hand contact with the mucous membranes of the eyes, nose, and mouth from being contaminated with the virus.

Contact Infection

If an infected person presses a sneeze or cough with his or her hand and then touches objects around him or her, the virus is transmitted.

If someone else touches it, the virus gets on your hand, and if you touch your mouth or nose with that hand, it's transmitted through the mucous membranes.

Thus, it refers to infection through the attachment of pathogens by indirect contact through the surface of an object.

Example: pharyngeal-conjunctival fever (pool fever), influenza, etc.

■Examples of the main sites where contact infection is likely to occur and countermeasures

  1. Doorknobs and bars → use elbows and arms

  2. Elevator buttons → use the back of your elbow or pinky finger

  3. Train and bus straps and catching bars → Can't get caught or use your little finger

  4. Stairway escalator handrail → do not touch

  5. Office common items (copy machine, PC, telephone) → Disinfect daily

■Examples of the main items that are prone to contact infection and countermeasures

  1. Cash → Go cashless! 

  2. Mask → When removing the mask, touch only the string.

  3. Gloves → When removing the gloves, take them off so as not to touch the surface as it is contaminated

  4. Smartphones → Do you put them in a zippered bag at home?

  5. Convenience store and supermarket baskets → It is advisable to disinfect the handles before using them.

  6. ATM screen → Hand hygiene after use!

  7. Public ballpoint pen → Carry your own pen and use it as much as possible.

Droplet Infection

It refers to when a virus or bacteria is bitten by fine saliva or respiratory secretions by coughing or sneezing, and jumps out into the air, infecting people within a distance of about one meter.

Example: whooping cough, colds, flu, mumps, etc.

Airborne Infection

It refers to when a virus or bacteria goes into the air and infects a person over 1m.

Example: measles, chicken pox, tuberculosis, etc.

Other Routes of Infection

■Oral infection (fecal-oral infection)

It is transmitted when food contaminated with viruses or bacteria is eaten raw or uncooked enough, or when an infected person contaminates food or water through his or her fingers or other means during cooking, and then eats or drinks that contaminated food.

Fecal-mouth infections are especially known when feces are ingested orally through the fingers.

Example: infectious gastroenteritis (rotavirus), infectious gastroenteritis (norovirus), etc.

■Blood infection

Example: HCV (hepatitis C), HBV (hepatitis B), syphilis, HIV (AIDS)

■Sexually transmitted diseases

Example: chlamydia, HIV, etc.

■Zoonotic infection

The transmission of pathogens in zoonotic diseases can be divided into two major categories: direct transmission from the animal as the source of infection to humans, and indirect transmission through the presence of some kind of medium between the animal and humans as the source of infection. Indirect transmission can be further divided into the following categories: pathogens in infected animals are transmitted to humans by arthropods (vectors), pathogens from the animal's body are transmitted to humans through the surrounding environment (water, soil, etc.), and foods such as livestock products are contaminated with pathogens.

Examples of direct transmission: rabies, cat scratch disease, toxoplasmosis, parrot disease, etc.

Examples of joint spread → malaria, yellow fever, Japanese encephalitis, dengue fever, West Nile fever, plague, tetanus, anisakis, etc.

What is a designated infectious disease?

The term refers to infectious diseases designated by the Law on Prevention of Infectious Diseases for a limited period of one year by decree. Diseases that can be transmitted from person to person are classified according to their infectiousness and risk.

The purpose is to prevent outbreaks by pre-determining measures such as advising patients to be admitted to the hospital and disinfecting the building.

The new coronavirus is designated as a category 2 infectious disease, like tuberculosis, SARS, and avian influenza (H5N1).

The Washington Post’s simulation of how the virus spreads shows why we must stay home to reduce infections and save lives.

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CONTRIBUTORSEditor : Mukai, Kuumuholn, Eisuke TachikawaIllustration : Kacho