Viral diseases are generally infections that occur due to a virus. These can spread through various ways, some get it by inhaling the virus, while others can get it by eating contaminated food or drinking contaminated water. 

Some of the common viral diseases are the common cold, flu, genital warts, cold sores, etc. 

In this article, we discussed some of the important points relating to viral diseases and their transmission. Read on to learn more about viruses and their mechanisms.

Viruses are generally described by the part of the body they affect or the signs and symptoms. So, the different types of viral infections are:

1. Congenital Infections: Congenital infections refer to those infections which a baby is born with. Generally, they pass from a pregnant mother to her foetus during the gestation period or the birth. 

Examples: Zika virus, Cytomegalovirus, Rubella virus, etc. 

2. Digestive System Infections: These infections affect your gastrointestinal tract, usually resulting in gastroenteritis, also known as the stomach flu. These viruses are generally contagious.

Examples: Norovirus, Rotavirus, Astrovirus, etc.  

3. Sexually Transmitted Infections: These are mainly spread through sexual intercourse, including oral sex, anal sex and vaginal sex.

Examples: Human immunodeficiency virus, Human papillomavirus, Herpes Simplex virus, etc. 

4. Exanthematous Infections: These infections manifest as skin rashes which may or may not be accompanied by additional symptoms. These are highly contagious. Therefore, the infected people are kept in isolation till their recovery. 

Examples: Rubella virus, Measles virus, variola virus, Varicella-zoster virus, etc. 

5. Respiratory Infections: These types of infections can affect our total respiratory pathway, which can cause several serious diseases resulting in respiratory distress.

Examples: Adenovirus, Respiratory syncytial virus, etc. 

6. Neurological Infections: Neurological infections occur in our brain and the surrounding tissues and damage our neurological functions. 

Examples: Poliovirus, rabies virus, etc. 

7. Viral Hemorrhagic Fevers: These viral infections affect your body’s circulatory system, generally showing up as high fever with chills. 

Examples: Ebola virus, Dengue virus, etc. 

Viral infections are transmitted in the following ways: 

• The virus gets transmitted through coughing, sneezing, or being in close proximity to the infected person. 
• From inanimate surfaces such as doorknobs, phones, etc. 
• Through different types of sexual intercourse. 
• After getting bitten by an infected animal or insect, in case of vector-borne diseases. 
• After eating contaminated food and water.

Viruses are unique organisms that cannot replicate on their own and always require a host cell to multiply.  So, after entering the human cells, they release their genetic material into the cell, which takes charge of the host cell and forces it to replicate the virus. 

After getting infected by the virus, usually, the host cell dies as the virus interferes with the normal functioning of the cell. This whole process kills the healthy cells of our body, eventually making us weak and sick.

The following section contains some of the diseases and their causative virus:

• Smallpox: Variola virus  
• Chickenpox: Varicella-zoster virus (VZV)
• Influenza: Influenza virus 
• Shingles: Varicella-zoster virus (VZV) 
• Herpes: Herpes simplex virus (HSV)
• Polio: Poliovirus 
• AIDS: Human Immunodeficiency Virus (HIV) 
• Severe Acute Respiratory Syndrome (SARS): SARS associated Covid virus 
• Measles: Measles Morbillivirus 
• Cervical Cancer: Human Papillomavirus

Different viruses have different clinical manifestations. However, some of the common signs and symptoms are:

• Irritability 
• Rashes 
• General malaise 
• Swollen tonsils 
• Sneezing 
• Flu-like symptoms: Sore throat, fever, and headache 
• Unexplained weight loss
• Blisters
• Warts 
• Vomiting 
• Diarrhoea
• Muscle ache 
• Seizures 
• Abdominal pain

Note: Some of the viral infections don’t have any signs and symptoms.

Our body has different efficient defence mechanisms through which it helps our body to fight any kind of infection. The primary barrier to any foreign body is the skin, which doesn’t allow easy access.

• After entering our body, the virus infects the healthy cells which then produce a chemical substance known as Interferons. These interferons protect the other healthy cells and make them impervious to the ongoing viral infection. 
• Subsequently, the body’s immune system also gets triggered by infection, and the white blood cells start to combat the infection. The white blood cells attack the virus and destroy them. Also, they produce certain antibodies that bind to the virus and turn them non-infectious.

However, some viruses, such as the human immunodeficiency virus, damage our body's immune system, and hence no protective response is produced from the body’s immunity. 

There are several viral diseases, some go away on their own within a few days, while some last for a long time and are serious. The viral infections cannot be treated with antibiotics, and hence, symptomatic management is undertaken. People tend to recover faster when combined with adequate rest and proper hydration.