Viral Infections: Types, Treatment and Prevention, Viruses and Cancer


The proliferation of a harmful virus inside the body is known as viral infection.

May 29, 2018

Viruses are small particles of genetic material either DNA or RNA that are surrounded by a protein coat. Some viruses also have a fatty envelope covering. They are incapable of reproducing on their own and depend on the organisms they infect for their very survival.
Viruses also perform many important functions for humans, plants, animals, and the environment. For example, some viruses protect the host against other infections.
Viruses also can transfer genes among different species helping in the process of evolution. These are the disease causing particles which can cause common cold, influenza, chickenpox, human immunodeficiency virus (HIV), and others. However, viruses can affect many areas in the body, including the reproductive, respiratory, and gastrointestinal systems. They can also affect the liver, brain, and skin.
The proliferation of a harmful virus inside the body is known as viral infection. Viruses cannot reproduce by itself. They need assistance of a host for this purpose. By introducing their genetic material into the cells, viruses infect a host and then hijack the cell's internal machinery to make more virus particles. A virus makes copies of itself and bursts the host cell to set the newly formed free virus particles.
Virus particles can also bud off the host cell over a period of time before killing the host cell. Either way, new virus particles are then free to infect other cells. As a result of cell damage, tissue destruction, and the associated immune response, there will be development of symptoms of the viral illness.
Certain viruses may be inactive or latent after the initial infection. For example in case of chickenpox and cold sores you may have a cold sore that erupts and then heals. But the virus remains in your cells in a dormant state. Over time it may reactivate and lead to new symptoms due to a a trigger, such as stress, sunlight, or something else. The virus makes more copies of itself, releases new virus particles, and kills more host cells.

Contagious Period:

The ability of a virus to be transmitted from one person or host to another is known as contagiousness. Depending on the virus, viral infections are contagious for varying periods of time. The time between exposure to a virus or other pathogen and the emergence of symptoms is known as an incubation period. The contagious period of a virus is not necessarily the same as the incubation period.

Virus Transmission  :

Viruses can be transmitted in several ways. Some viruses can spread through touch, saliva, or close contact with the infected person. Other viruses can be transmitted through sexual contact or by sharing contaminated needles. Insects including ticks and mosquitoes can act as a source in transmitting a virus from one host to another. Contaminated food and water are other potential sources of viral infection. It can also get spread through air when a person sneeze and cough.

Types of Viral Infections:

Viral Infections can be of many types. These include:

Respiratory Viral Infections:

Usually the lungs, nose, and throat gets affected in respiratory viral infections. When an infected person cough or sneeze, droplets containing virus particles will be there in the air which can easily get spread to a healthy person by inhaling these droplets.
Examples include:

Rhinovirus:

This virus most often causes the common cold. But there are more than 200 different viruses that can cause colds. Symptoms include coughing, sneezing, mild headache, and sore throat which usually last for up to 2 weeks.

Seasonal influenza:

This is the most common illness caused by virus which include body aches and severe fatigue. Flu symptoms are more severe than cold symptoms and also tends to come on more suddenly than a cold.

Respiratory Syncytial Virus (RSV):

This is an infection that can cause both upper respiratory infections like colds and lower respiratory infections such as pneumonia and bronchiolitis. It can be very severe in infants, small children, and elderly adults. To help reduce the spread of respiratory infections, you should frequent wash your hand, cover the nose and mouth when coughing or sneezing, and avoid contact with infected individuals. Do not touch the eyes, nose, and mouth when comes in contact with an infected person.

Viral Skin Infections:

Viral skin infections can range from mild to severe and often produce a rash. . Examples of viral skin infections include:

Molluscum contagiosum:

It causes small, flesh-colored bumps most often in children ages 1 to 10 years old. However, people of any age can acquire the virus. Usually the bumps disappear without treatment in 6 to 12 months.

Herpes simplex virus-1 (HSV-1):

This is the common virus that causes cold sores. It is transmitted through saliva by kissing or sharing food or drink with an infected individual. Sometimes, HSV-1 causes genital herpes.

Varicella-zoster virus (VZV):

It causes itchy, oozing blisters, fatigue, and high fever characteristic of chickenpox. The chickenpox vaccine is almost effective in preventing infection. People who have had chickenpox or people who have received the chickenpox vaccine are at risk for developing shingles, an illness caused by the same virus which is very rare. Shingles can occur at any age, but it occurs most often in people age 60 or older.
The best way to avoid viral skin infections is to avoid skin-to-skin contact, especially areas that have a rash or sores with an infected individual. Some viral skin infections, such as varicella-zoster virus, are also transmitted by an airborne route. Communal showers, swimming pools, and contaminated towels can also potentially harbor certain viruses.
Precautions can be taken in all these cases to prevent skin infection.

Foodborne Viral Infections:

one of the most common causes of food poisoning are viruses. The symptoms of these infections vary depending on the virus involved.

Hepatitis A :

This virus affects the liver for a few weeks to several months. Symptoms may include yellow skin, nausea, diarrhea, and vomiting. There is possibility of recurrent illness within 6 months of infection.

Norovirus:

This virus is responsible for outbreaks of severe gastrointestinal illness that happen on cruise ships. However it causes disease in many situations and locations.
Many cases of viral gastroenteritis, which causes inflammation of the stomach and intestines can be due to norovirus. This can be refer as stomach flu which causes nausea, vomiting, diarrhea, and abdominal pain.

Rotavirus:

It causes severe, watery diarrhea that can lead to dehydration. Anyone can get rotavirus, but the illness occurs most often in babies and young children.
Many cases of viral gastroenteritis, which causes inflammation of the stomach and intestines can be due to rotavirus. This can be refer as stomach flu which causes nausea, vomiting, diarrhea, and abdominal pain.
Most of the time foodborne viral illnesses are transmitted through the fecal oral route. A person can get the virus by ingesting virus particles that were shed through the feces of an infected person. Indivisuals with this type of virus can transfer the virus to others by shaking hands, preparing food, or touching hard surfaces when they do not wash their hands after using the restroom. Contaminated water is another potential source of infection.

Sexually Transmitted Viral Infections:

Sexually transmitted viral infections spread through contact with bodily fluids that include semen, vaginal and rectal fluids, blood, and breast milk.
Examples include:

Human papillomavirus (HPV):

This is the most common sexually transmitted infection which can cause genital warts. There are many different types of HPV. These can increase the risk of cervical cancer.
The HPVs (human papillomaviruses) can be spread from person to person or can be acquired through contact with a contaminated surface. HPV viruses cause the excessive and rapid growth of keratin, which is a hard protein on the top layer of the skin. Different warts are caused by different HPV strains. The virus can be spread by close skin to skin contact, and through contact with towels or shoes. In women, they can lead to cervical, anal, and vulvovaginal cancer which could be fatal, where as in men, anal cancer and cancer of the glans penis can also occur as a result of infection with some types of genital warts. Most of the cancer causing strains of HPV can be prevented by vaccination.

Hepatitis B:

It causes inflammation in the liver. It can be transmitted through contaminated bodily fluids that include semen, vaginal and rectal fluids, blood, and breast milk. Some people with the virus don't experience any symptoms while others can have the symptoms similar to flu. The hepatitis B vaccine can be effective in preventing infection.

Herpes simplex virus-2 (HSV-2) and Herpes simplex virus-1 (HSV-1):

It can cause Genital herpes which is a common sexually transmitted infection. Herpes simplex virus-1 (HSV-1) is responsible for cold sores. It can also sometimes cause genital herpes. There is no cure for genital herpes. Painful sores often recur during outbreaks. Antiviral medications are often use to decrease both the number and length of outbreaks.

Human immunodeficiency virus (HIV):

It is a virus that affects certain types of T cells of the immune system making people much more vulnerable to infections and diseases. Progression of the infection decreases the ability of your body to fight disease and infection, leading to acquired immune deficiency syndrome (AIDS). HIV is transmitted by coming into contact with blood or bodily fluids of an infected person. The virus does not spread in air or water, or through casual contact. Currently there is no cure for HIV.
The risk of getting a sexually transmitted viral infection can be reduced by avoiding sex or having sex with only one partner who does not have a sexually transmitted infection. Using a condom decreases the risk of acquiring a sexually transmitted infection. But it doesn't completely eliminate the risk. Minimizing the number of sexual partners and avoiding intravenous drug use are other ways to reduce the risk of acquiring sexually transmitted viral infections.

Other Viral Infections:

Viruses are present everywhere in the environment and cause many other infections ranging from mild to severe.
Examples include:

Epstein-Barr virus (EBV):

This is a type of herpes virus that can cause fever, fatigue, swollen lymph nodes, and an enlarged spleen. EBV is a very common virus that causes mononucleosis. This  is also known as kissing disease that is spread primarily through saliva.

West Nile virus (WNV):

This is a virus that is most commonly transmitted by infected mosquito. Most of people with WNV don't experience any symptoms while others can develop a fever, headache, and other symptoms. In very rare case people with WNV can develop inflammation of the brain (encephalitis) or inflammation of the tissue surrounding the brain and spinal cord (meningitis).

Enteroviruses:

Many viruses can cause viral meningitis. Enteroviruses is the most common virus causing viral meningitis which is an inflammation of the lining of the brain and spinal cord. Headache, fever and stiff neck, are the most common symptoms of this condition.

Antiviral Medication and Other Treatment:

Most of the viral infections resolve on their own without treatment. However, if treatment of viral infections is required, it will be focused on symptom relief, not fighting the virus. For example, cold medicine helps alleviate the pain and congestion associated with the cold, but it doesn't act directly on the cold virus.
Antiviral medications are medications that work directly on viruses. They work by inhibiting the production of virus particles. Some interfere with the production of viral DNA where as others prevent viruses from entering host cells.
Antiviral medications are most effective when they are taken in early stage of viral infection or a recurrent outbreak. Different kinds of antiviral medications may be used to treat chickenpox, shingles, herpes simplex virus-1 (HSV-1), herpes simplex virus-2 (HSV-2), HIV, hepatitis B, hepatitis C, and influenza.

Viruses and Cancer:

Viruses introduces themselves to host cell DNA in order to make their copies. Cancer is a disease that occurs as the result of mutations or alterations to DNA. Because viruses affect the DNA of host cells, viruses can contribute to several different types of cancer. Viruses known to increase the risk of cancer include:

  • Epstein-Barr virus (EBV) for nasopharyngeal cancer, Burkitt lymphoma, Hodgkin's lymphoma, and stomach cancer
  • Hepatitis B and hepatitis C for liver cancer
  • Human papilloma virus (HPV) for cervical cancer
  • Human T-lymphotrophic virus-1 (HTLV-1) for T-cell leukemia/lymphoma (ATL)
  • Human immunodeficiency virus (HIV) for Kaposi sarcoma, invasive cervical cancer, lymphomas, and other cancers
  • Merkel cell polyomavirus (MCV) for a rare skin cancer called Merkel cell carcinoma

Prevention of viral infection:

The risk of acquiring some viral illnesses can be prevented by vaccination. Vaccines are available to help protect against the flu, hepatitis A, hepatitis B, chickenpox, herpes zoster (shingles), measles/mumps/rubella (MMR), polio, rabies, cancer-causing strains of human papillomavirus (HPV), rotavirus, and other viruses.
The effectiveness of vaccine may vary. The the number of doses required to confer protection may also vary. Some vaccines require booster shots to maintain immunity.
In general you can follow the following tips to prevent viral infection:

Clean your hands properly:

Proper hand cleaning is the best way to prevent all kinds of infections and maintain a good hygiene. That is why it is important to clean your hands regularly and properly using soap and water or an alcohol-based hand sanitizer especially before handling food and after using toilet. You should teach your children how to clean their hands regularly and maintain proper hygiene.

Cover your mouth when you cough or sneeze:

Teach your children to cover their mouths when they cough or sneeze. You can also cover your mouth and nose when somebody around you cough or sneeze to avoid breathing airborne droplets.

Do not share personal items:

Do not share drinking glasses or eating utensils with anyone. Before using wash dishes in hot, soapy water or in a dishwasher.