ADENOVIRUS INFECTION

Adenoviridae are a diverse group of viruses that infect humans and a wide range of animal hosts. These viruses are classified as non-enveloped viruses, meaning they lack a surrounding lipid membrane, a feature that contributes significantly to their environmental stability and resistance to harsh conditions. Structurally, adenoviruses possess an icosahedral nucleocapsid, which is a symmetrical protein shell composed of capsomeres that enclose and protect the viral genetic material. The genome of adenoviruses consists of a linear, double-stranded DNA molecule, allowing them to replicate efficiently within the nucleus of infected host cells.

Adenoviruses are medically important pathogens because they are associated with a variety of human diseases. They commonly infect the respiratory tract and are well known for causing illnesses such as the common cold, pharyngitis, bronchitis, croup, and pneumonia. In addition to respiratory infections, adenoviruses can also cause conjunctivitis, often referred to as “pink eye,” as well as gastrointestinal infections that result in diarrhea and abdominal discomfort. In children, adenoviral infections are especially common because of their developing immune systems and close contact in schools or daycare environments. Pediatric infections frequently involve both the respiratory and intestinal tracts, leading to symptoms such as fever, sore throat, cough, runny nose, vomiting, and diarrhea.

Transmission of adenoviruses occurs primarily through respiratory droplets, direct personal contact, or contact with contaminated surfaces and objects. The viruses may also spread through water, particularly in inadequately chlorinated swimming pools, where outbreaks of conjunctivitis and respiratory disease have been documented. One of the distinguishing characteristics of adenoviruses is their remarkable ability to survive outside the human body for extended periods. Unlike many enveloped viruses, adenoviruses are resistant to environmental stress because they do not possess a fragile lipid envelope. They can withstand adverse pH conditions and are relatively resistant to several chemical disinfectants and physical agents. This environmental persistence increases their potential for transmission in both healthcare and community settings.

Although many adenoviral infections are mild and self-limiting, severe disease can occur in immunocompromised individuals, infants, and the elderly. For this reason, adenoviruses remain an important subject of study in virology, public health, and infectious disease research.

SYMPTOMS OF ADENOVIRUS INFECTION

Adenoviruses can cause a wide range of illnesses such as:

• Common cold

• Sore throat

• Bronchitis (a condition that occurs when the airways in the lungs become filled with mucus and may spasm, which causes a person to cough and have shortness of breath)

• Pneumonia (infection of the lungs)

• Diarrhea

• Pink eye (conjunctivitis)

• Fever

• Bladder inflammation or infection

• Inflammation of stomach and intestines

• Neurologic disease (conditions that affect the brain and spinal cord)

Adenoviruses can also cause mild to severe illness, though serious illness is less common. People with weakened immune systems, or existing respiratory or cardiac disease, are at higher risk of developing severe illness from an adenovirus infection.

TRANSMISSION OF ADENOVIRUS INFECTION

Adenoviruses are usually spread from an infected person to others through:

• close personal contact, such as touching or shaking hands

• the air by coughing and sneezing

• touching an object or surface with adenoviruses on it, then touching your mouth, nose, or eyes before washing your hands

• adenoviruses are majorly spread via respiratory droplets

• they can also be spread via the feacal oral route

Some adenoviruses can spread through an infected person’s stool, for example, during diaper changing. Adenovirus can also spread through the water, such as swimming pools, but this is less common.

Sometimes the virus can be shed (released from the body) for a long time after a person recovers from an adenovirus infection, especially among people who have weakened immune systems. This “virus shedding” usually occurs without any symptoms, even though the person can still spread adenovirus to other people.

OUTBREAKS CAUSED BY ADENOVIRUS INFECTION

Outbreaks of adenovirus infection can occur throughout the year. They are usually associated with respiratory illnesses or conjunctivitis.

Reported sporadic cases and outbreaks of adenovirus have included:

• Adenovirus types 3, 4 and 7, which are most commonly associated with acute respiratory disease

• Adenovirus type 14, which since 2007 has been associated with outbreaks of acute respiratory illness among U.S. military recruits and the general public

• Adenovirus types 8, 19, 37, 53, and 54, which can cause epidemic keratoconjunctivitis

• Enteric adenovirus types 40 and 41, which cause gastroenteritis, usually in children

• Some adenoviruses (e.g., 4 and 7) that spread in bodies of water such as small lakes or swimming pools without adequate chlorine and can cause outbreaks of febrile disease with conjunctivitis

Health Professionals should:

• Consider adenoviruses as possible causes of upper respiratory illness, and lower respiratory illness such as pneumonia

• Report unusual clusters of illness (e.g., respiratory, conjunctivitis) potentially caused by adenoviruses to the state or local health department

PREVENTION OF INFECTION CAUSED BY ADENOVIRUS

There is currently no adenovirus vaccine available to the general public. However, adenovirus vaccine is available for U.S. military only.A vaccine specific for adenovirus types 4 and 7 was approved by the U.S. Food and Drug Administration (FDA) in March 2011, for use only in U.S. military personnel who may be at higher risk for infection from these two adenovirus types.

Follow simple steps to protect yourself and others:

You can protect yourself and others from adenoviruses and other respiratory illnesses by following a few simple steps:

• Wash your hands often with soap and water

• Avoid touching your eyes, nose, or mouth with unwashed hands

• Avoid close contact with people who are sick

If you’re sick you can help protect others:

• Stay home when you are sick

• Cover your mouth and nose when coughing or sneezing

• Avoid sharing cups and eating utensils with others

• Refrain from kissing others

• Wash your hands often with soap and water, especially after using the bathroom

Frequent hand washing is especially important in childcare settings and healthcare facilities.

Maintain proper chlorine levels to prevent outbreaks

Adenoviruses are resistant to many common disinfectant products and can remain infectious for long periods on surfaces and objects. It is important to keep adequate levels of chlorine in swimming pools to prevent outbreaks of conjunctivitis caused by adenoviruses.

 TREATMENT OF ADENOVIRUS INFECTION

There is no specific treatment for people with adenovirus infection. Most adenovirus infections are mild and may require only care to help relieve symptoms. Adenovirus infection is usually benign in nature, and is usually self-limiting in nature.

Good hygiene, including proper hand washing using disinfectants or detergents, is still the best way to avoid picking up the adenovirus from an infected person.

Other methods of preventing and controlling the spread of adenovirus infection in human population include: covering your mouth while coughing and sneezing, avoiding shared cups and utensils, and even refraining from kissing as vigilant precautionary measures against the stubborn adenovirus, for which there is no known cure.

SOURCE:

Center for Disease Control and Prevention (CDC)