infection

Each of us sometimes may "catch" some cold or flu, so we are not feeling well. Or, we have a sore throat. Or, suppose you cut yourself. So we are reacting fast to clean the cut, to avoid any further issues. We know that the injured place can hurt, turns red, swell, or even some fluids may leak from it, so we want to prevent that. What do you think, why is that happening? And, can you think of something that is common in these cases?

All of the above cases are examples of different INFECTIONS. Do you know what infections are?

What are infections, how do they occur, are they serious and can they be treated, you can find out by reading this lesson!

What is an infection?

If we think about the case of the cut and suppose that it turned red and swell,  it is not because there is a wound, it is because germs entered and now the wound is infected.

When microorganisms enter the human body and cause harm, then occur an infection. These infectious microscopic organisms are known as pathogens, infectious agents, germs, etc. Examples of pathogens include viruses, bacteria, fungi, and parasites.

You can find pathogens in the air, on food, plants, and animals; in the soil, water, surfaces, human skin, etc. So, we are exposed to pathogens all the time. But, the immune system has a vital role, because it protects our bodies from them. A healthy immune system can defeat invading disease-causing pathogens.

An infection occurs when 1. germs enter the body, 2. increase in number, and 3. cause a reaction in the body.

Infections can begin anywhere in the body and then may spread all over the body. An infection can cause health problems, which differ depending on where it occurs in the body. 

Although not all infections result in disease, some can trigger the immune system, causing symptoms of illness.

Microorganisms capable of causing disease, usually enter our bodies through the eyes, mouth, nose, or urogenital openings, or through wounds or bites that breach the skin barrier. 

Types of infections:

We now know that infections can be caused by viruses, bacteria, fungi, and parasites.

So, infections may be:

1. Viral, caused by viruses. Viruses cause illness by killing cells or interfering with cell function. The virus infiltrates a host's body and attaches itself to a cell, where it releases its genetic material. The virus multiplies as the cell replicates. When a cell dies, more viruses are released, infecting new cells. Some viruses alter the function of cells rather than killing them. Most viral infections are self-limiting, and the immune system may be able to fight them off.
2. Bacterial, caused by bacteria.  Bacterial infection occurs when one or more bacteria have entered the body and begin to multiply. If needed, these infections are usually treated with antibiotics.
3. Fungal, caused by fungi. Some fungi occur naturally in the body, and they can be helpful or harmful. An infection occurs when an invasive fungus becomes too much for the immune system.
4. Parasitic infection describes the infection of a host with a particular parasite.

Infectious Diseases

An infectious disease, also known as transmissible disease or communicable disease, is an illness resulting from an infection. The five periods of disease (sometimes referred to as stages or phases) include the incubation, prodromal, illness, decline, and convalescence periods. 

1. Incubation

When the pathogen enters the host, that is the incubation period. Patients at this point are usually unaware that are going to be sick. This is the time when pathogen starts to multiply in the body. Depending on the pathogen, this period can vary from hours or days in acute diseases to months and years in chronic diseases.  

2. Prodromal 

The prodromal period occurs after the incubation period. Now, the pathogen continues to multiply,  and the host begins to experience general signs and mild, nonspecific symptoms of illness. This is a result of the activation of the immune system. Signs and symptoms depend on the type of the infection and can be fever, pain, swelling, or inflammation. During the prodromal stage, people can transmit infections. 

3. Illness

Following the prodromal period is the period of illness. During this period the signs and symptoms of the disease are most obvious, severe, and specific. The symptoms of infection vary a lot, depending on which is the underlying cause.

4. Decline

The period of illness is followed by the period of decline. During this period, the number of pathogens starts to decrease, which results in a decline in signs and symptoms of illness. But, during the decline period, patients may become susceptible to developing secondary infections. That is because their immune systems have been already weakened by the primary infection. The virus can be still transmitted to other people during the decline period. 

5. Convalescence

This is the final period and is known as the period of convalescence, and during this stage, symptoms resolve. Now, the patient generally returns to normal functions, although sometimes permanent damage can be caused by the disease.

Some common infectious diseases, grouped by the pathogen that causes them, are:

Bacterial

• Bacterial meningitis
• Otitis media
• Bacterial pneumonia
• Tuberculosis
• Strep throat

Viral

• Chickenpox
• Herpes
• HIV/AIDS
• Infectious mononucleosis
• Influenza (flu)

Fungal

• Athlete's foot
• Candidiasis

Parasitic

• Cysticercosis, or tapeworm
• Toxocariasis, or roundworm
• Malaria

Signs and symptoms

Signs and symptoms of an infection may vary depending on the pathogen that's causing it, and where is infection located. However, some general symptoms of infections include:

• Fever, which is sometimes the only sign of an infection
• Chills and sweats
• Nasal congestion
• Change in cough or a new cough
• Sore throat or new mouth sore
• Shortness of breath
• Stiff neck
• Burning or pain with urination

Chain of infection

The spread of an infection within a community is described as a “chain,” with several interconnected steps that describe how a pathogen moves about. The 6 points include:

1. The infectious agent.
   Infectious agents are organisms that are capable of producing infection or infectious disease.
2. Reservoir. 
   The reservoir of an infectious agent is the habitat in which the agent normally lives, grows, and multiplies. Reservoirs include humans, animals, and the environment.
3. Portal of exit.
   Portals of exit are the means by which a pathogen exits from a reservoir. For a human reservoir, the portal of exit can include blood, respiratory secretions, and anything exiting from the gastrointestinal or urinary tracts.
4. Means of transmission.
   The mode (means) of transmission is the route or method of transfer by which the infectious microorganism moves or is carried from one place to another to.
5. Portal of entry.
   A portal of entry is the site through which micro-organisms enter the susceptible host and cause disease/infection. Infectious agents enter the body through various portals. They include inhalation (via the respiratory tract), absorption (via mucous membranes such as the eyes) and ingestion (via the gastrointestinal tract).
6. Susceptible host. 
   The host is any carrier of infection or someone at risk of infection.

How do infections spread?

Infectious diseases commonly spread through the direct transfer of bacteria, viruses, or other pathogens from one person to another. Pathogens that cause infections can be spread in several ways:

1. Through the air. This happens usually in droplets that are sneezed, coughed, or breathed out in the air by the infected person. Some pathogens like those that cause influenza, can travel short distances. Other pathogens such as those that can cause chickenpox, stay in the air longer and can travel longer distances.
2. By contact. The contact can be direct or indirect. Some diseases need direct person-to-person contact with an infected person, and in other cases, pathogens are spread by contact with an object that has pathogens on it. Some of the infectious diseases spread by contact are conjunctivitis (Pink Eye) and herpes simplex. Infestations such as ringworm, head lice, scabies, and pinworms are also spread by contact.
3. Through blood or body fluids. Some of the diseases spread in this way are HIV/AIDS, hepatitis B, and hepatitis C.
4. By a common source, like food poisoning, which happens when food or water is contaminated.
5. By insects or animals. Mosquitoes, rats, mice, flies, and other animals can carry harmful germs that cause illness. Malaria is an example of a disease caused by a bite of an infected mosquito.

Preventing infections

Good hygiene is the primary way to prevent infections:

1. Washing hands 
2. Covering mouth and nose when having a cough
3. Washing and bandaging all cuts
4. Do not pick at healing wounds or blemishes, or squeeze pimples
5. Don't share dishes, glasses, or eating utensils
6. Avoid direct contact with napkins, tissues, handkerchiefs, or similar items used by others