Adenovirus

Overview

Adenovirus is a type of virus that most commonly causes upper and lower respiratory infections. It can also cause a variety of other illnesses, including gastrointestinal infection, neurological infection, and eye infection. Its outbreaks can occur throughout the year and may spread more quickly in closed populations. Disease is usually mild and self-limiting. Severe disease is a possibility in immunocompromised patients or those with existing respiratory or cardiac disease. Treatment is symptomatic and supportive.

Although, recombinant adenoviruses currently are used for a variety of purposes, including gene transfer in vitro, vaccination in vivo, and gene therapy. Several features of adenovirus biology have made such viruses the vectors of choice for certain of these applications.

Epidemiology

Human adenoviruses (HAdVs) are members of the Adenoviridae family. The name derives from the initial isolation of the virus from human adenoids in 1953. Adenoviruses are medium-sized (70–100 nm), nonenveloped double-stranded DNA viruses with an icosahedral nucleocapsid.

Currently, there are 104 different HAdV types known, which have been classified into seven species A to G based on the percentage of guanine plus cytosine in their DNA and other biochemical and biophysical criteria.

Adenovirus infection in humans are generally caused by Adenoviruses types B, C, D, E and F. Specific serotypes are often associated with clinical syndromes. Adenovirus types 3, 4 and 7 are most commonly associated with acute respiratory illness. Adenovirus types 4 and 7 have been associated with more severe outcomes than other adenovirus types, particularly in people with weakened immune systems.

Host

Children and immunocompromised patients or those with existing respiratory or cardiac disease, are at increased risk for infection. Adults who are in closed or crowded environments, are also at higher risk.

Incubation period

The incubation period for Adenovirus is 2–14 days.

Period of communicability

Adenovirus infections are most contagious during the first few days of symptoms. 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.

Transmission

Adenoviruses are usually spread from an infected person to others through

• close personal contact, such as touching or shaking hands
• through 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
• contact with stool, for example, during diaper changing
• Adenovirus can also spread through water of swimming pools and small lakes

Case identification

Probable:

• ILI (Influenza Like Illness) - Any person with an acute respiratory infection (sudden cough and sore throat) with measured fever of ≥ 38⁰C (≥ 100.4 F); with onset within the last 10 days
• SARI (Severe Acute Respiratory infection - Any person with an acute respiratory infection (sudden cough and sore throat) with measured fever of ≥ 38⁰C
  (≥ 100.4 F); with onset within the last 10 days AND Requires hospitalization

Confirmed:

A presumptive case of ILI or SARI with 

• Conventional PCR or real-time PCR OR
• Any validated nucleic acid-based test.

Management

There is no specific treatment or approved antiviral medicine for people with adenovirus infection. Primary Prevention is the mainstay.

Clinical care of adenovirus infections includes treatment of symptoms and complications. Most adenovirus infections are mild and may only require care to help relieve symptoms.

Rest, plenty of fluids and over-the-counter pain medicines or fever reducers are advised to help relieve symptoms. To categories treatment:

• In immunocompetent host with mild to moderate disease: It consists primarily of supportive care. One is advised to maintain proper hydration, anti-pyretic for fever, anti-emetic for vomiting, oxygen support in case of pneumonia or ARDS, and bed rest.
• In immunocompetent host with severe disease: No proven role of anti-viral therapy has been established. Still the pre-emptive treatment is followed with supportive care to the organs involved.
• In immunocompromised patients: These group of patients mainly include those with solid organ transplants and stem cell transplants. Cidofovir is the only recognized anti-viral agent used. It is mainly used in stem cell transplant. Dosage: 1mg/kg intravenous twice weekly or 5mg/kg every one to two weeks. Adverse effect is nephrotoxicity.
• IVIGs plus Cidofovir have also been used in stem cell transplants patients which is giving promising results.

For epidemic conjunctivitis, a cold compress and lubricants may provide some relief of discomfort. Patients who are seriously ill with persistent high fever,  breathing problems, change in vision, severe dehydration etc. may need care in the hospital to help them recover.

Preventive measures

Raising awareness of risk factors and educating people about the measures they can take to reduce exposure to the virus is the main prevention strategy. These include:

Non- pharmaceutical Interventions-(NPI)

NPIs include both actions that individuals and households can take (e.g. frequent hand washing, covering coughs and sneezes, and keeping a distance from sick people).

Personal NPIs include:

• Masking provides an extra layer of protection against viral illnesses and are strongly recommended in crowded places.
• Hand hygiene- Wash hands regularly, and as soon as possible after sneezing or coughing. Use soap and water and wash for 20 seconds. Use an alcohol-based hand sanitizer if one can’t wash hands with soap and water.
• Avoid sharing cups, glasses and cutlery with people who are sick. Regularly wash or wipe down utensils and surfaces with a household cleaner that contains soap or detergent.
• Respiratory etiquettes: Cover nose and mouth with a tissue when coughing and sneezing or use elbow. Don’t use hands. Dispose of tissues straight away in a bin. Do not spit in public places.
• Isolation: Stay at home if one feels unwell so he/she doesn’t pass their virus to other people.

Environmental non-pharmaceutical interventions

Adenoviruses are resistant to many common disinfectants and can remain infectious for hours on environmental surfaces and medical instruments.

To prevent spread of adenoviruses, use of recommended & registered disinfectants like quaternary ammonium, hydrogen Peroxide, paracetic acid and hypochlorous acid on surfaces that is effective at killing adenoviruses and compatible with the surfaces and equipment is advised.

Disinfectants effective against norovirus should also be effective against adenoviruses. Follow guidelines of Infection Control Practices.

Maintain proper chlorine levels to prevent outbreaks: It is important to keep adequate levels of chlorine in swimming pools to prevent outbreaks of conjunctivitis caused by caused by adenoviruses.

In health care settings:

• PPE: Use of appropriate personal protective equipment (PPE) when caring for patients.
• BMW: Correct containment and disposal of contaminated waste (e.g., dressings) in accordance with Biomedical Waste Management guidelines for infectious waste.
• Airborne control measures include ventilation, air filtration, reducing crowding, wearing masks whenever indoors (even if not within 6 feet or 2 meters of others), attention to mask quality and fit, and higher-grade PPE for healthcare and other staff when working in contact with potentially infectious people
  adenoviruses

Source : CD Alert - National Centre for Disease Control, Directorate General of Health Services, Government of India