Infections caused by viruses are called viral infections. Viruses are tiny pathogens that use a person’s cells to replicate repeatedly. They usually cause digestive and respiratory illnesses, but some variants can also affect other body functions. Common viral illnesses include the flu, cold, and herpes (cold sores). These go away on their own in most cases but can sometimes cause life-threatening or chronic health problems. Here are the types and early symptoms of viral infections.

Types of viral infections
Viral infections are usually classified depending on the body part they infect, how they spread, and the symptoms they cause. Certain viruses, such as adenovirus and herpes virus, can cause different health problems. The common types of viral infections include the following:

Respiratory viral infections
Respiratory viral infections start in the lungs, airways, throat, and nose. These infections cause pneumonia, ear infections, sinusitis, and bronchitis. Some common types of respiratory viral infections include:

• Common cold, which is generally caused by rhinovirus
• Flu caused by influenza
• Respiratory syncytial virus (RSV)
• Human metapneumovirus (hMPV)
• Parainfluenza

Viral infections in the digestive system
Viral infections can affect any part of the digestive system but usually start in the stomach, intestines, gastrointestinal tract, or liver. Some common types of digestive system viral infections include the following:

• Norovirus, astrovirus, and rotavirus cause gastroenteritis, also called stomach flu.
• The hepatitis virus causes an infection in the liver, which can last long, leading to chronic health problems.

Viral hemorrhagic fevers
This type of viral infection affects the blood clotting process. It weakens the blood vessels, leading to chronic and sometimes life-threatening bleeding. Some common types of viral hemorrhagic fevers include the following:

• Ebola
• Hantavirus pulmonary syndrome (HPS)
• Severe dengue
• Yellow fever

Sexually transmitted viral infections
Sexually transmitted viral infections are usually spread through intercourse. Common examples of this type of viral infection include the following:

• Human immunodeficiency virus (HIV)
• Human papillomavirus (HPV) or genital warts
• Genital herpes (caused by the herpes simplex virus, or HSV)
• Hepatitis B

Exanthematous viral infections
These infections trigger rashes that look like blisters and bumps on the skin’s surface. The rashes can also appear as spots of blood under the skin. Exanthematous viral infections can cause respiratory symptoms. Some common types of this infection are:

• Chickenpox
• Measles
• Rubella or German measles
• Roseola
• Fifth disease
• Monkeypox

Neurological infections
Specific viruses infect the cells of the nervous system, including the spinal cord and the brain. They can cause symptoms like paralysis, swelling of brain tissues, encephalitis, and meningitis. Some common types of neurological infections include the following:

• West Nile virus
• Polio
• Rabies

Congenital viral infections
Congenital viral infections are health disorders a person has had since birth. They usually pass on from the mother to the fetus during development but can also occur at birth. Based on the type of the virus, the patient may develop problems like loss of hearing or vision, neurological problems, and developmental delays. The following viruses can cause congenital viral infections:

• Cytomegalovirus (CMV)
• Rubella
• Zika virus

Early symptoms of viral infections
The signs may vary depending on the type of viral infection. However, specific early symptoms are common in most cases.

Flu symptoms
When down with the flu, one may experience the following:

• Fever
  One’s immune system gets activated when a virus infects any body part, sending white blood cells and antibodies to fight the virus. Consequently, there is a rise in the temperature of the body, leading to fever. The fever is often accompanied by other symptoms like a runny nose, cold, and cough.
• Headache
  Infections caused by viruses lead to inflammation in the body, which, in turn, triggers severe headaches. The cold and fever caused by the viral infection can worsen the headache.
• Fatigue
  Fatigue is usually a common early symptom of viral infection. It lasts until all the viruses in the body have been destroyed. However, some people develop post-infection fatigue, lasting a couple of days.
• Body ache
  As mentioned, an infection due to any pathogen, including viruses, causes the immune system to release white blood cells. These cells defend the body and destroy the viruses but cause inflammation and body aches in the process. One may experience mild to severe muscle pains as well.

Upper respiratory viral infection symptoms
Viral infections can cause symptoms in the upper respiratory tract, too. Some of these early symptoms include the following:

• Nasal congestion
  Patients may develop fluid accumulation in the nasal canal and sinuses as their immune system tries to fight the infection. This accumulation of fluids can cause nasal congestion.
• Sore throat
  This is among the most common early symptoms of viral infections, caused due to pharynx inflammation. The inflammation usually goes away on its own without treatment. Home remedies like sipping hot ginger or peppermint tea and gargling provide temporary relief.
• Cough
  Most viral infections cause lung, throat, and windpipe inflammation, leading to mild to severe cough. This type of cough usually goes away in a couple of weeks.
• Sneezing
  This symptom usually develops when the viral infection occurs in the nasal passage. In such cases, the immune system releases inflammatory compounds like histamines to fight the infection. It causes dilation and leakage of blood vessels. Consequently, the mucus glands release nasal fluids, causing sneezing episodes.

Digestive symptoms of viral infections
One may experience the following digestive discomforts during a viral infection:

• Nausea and vomiting
  Particular viral infections bring about feelings of nausea and vomiting in the early stages.
• Diarrhea
  It is a common symptom that affects the digestive tract or stomach. Diarrhea generally develops a few days after exposure to the virus. It goes away in a couple of days but may persist for a longer period in some cases.

Learning about the types and early symptoms of viral infections can help patients be better prepared to manage their health situation.