Medical Author : Charles Patrick Davis, MD, PhD
Medical Editor : Melissa Conrad Stöppler, MD
Adenovirus 14 (Ad14) facts
- Adenovirus 14 (Ad14) is termed the killer cold virus because of the high incidence of hospitalizations and deaths attributed to the viral strain.
- Ad14 viruses are passed person to person or picked up from items touched by infected people and then initially invade cells in the eye, nose, or mouth that subsequently allow further spread to other body organs.
- Symptoms and signs resemble those of a cold (cough, runny nose, mild fever) for about three to five days; the majority of people clear the disease, but up to about 40% may need hospitalization with severe symptoms of pneumonia, and shortness of breath; other organ related symptoms may develop such as eye, bladder, and GI problems.
- Ad14 is presumptively diagnosed by history, physical exam, X-ray, and in association with other Ad14-diagnosed patients in the community; definitive diagnosis is completed with isolation of the virus from the patient, a rising titer of antibodies against Ad14, immunofluorescence of Ad14 virus particles in tissues, or fluids and PCR tests.
- Treatments are mainly supportive; antivirals have been used by some clinicians but there are no studies that prove efficacy, only case reports.
- Complications of Ad14 are related to the severity of infection; the majority of patients have no complications but hospitalized patients may have mild to serious complications which are related to the organ system most damaged (eyes, GI tract, bladder and most notably, lung problems such as ARDS that may lead to death).
- The majority of patients have an excellent prognosis; however, about 40% of infected patients may have a wide range of suboptimal outcomes, depending on the severity of the Ad14 infection.
- Ad14 infections can be reduced or prevented by careful hygiene methods; there is no vaccine currently available against Ad14.
What is the killer cold virus?
The term "killer cold virus" was applied to a new strain of Adenovirus termed adenovirus 14 or Ad14 that appeared in several outbreaks (2005, 2007, 2008 and 2009-10 in Ireland) and that caused severe pneumonia and deaths in several different groups of individuals. This term was used because, in most people, adenoviruses cause symptoms of the common cold, not severe pneumonia or death. Investigations done by state and city health authorities, the U.S. Air Force, and CDC during several outbreaks showed that Ad14 is a rarely reported but emerging serotype of adenovirus that can cause severe and sometimes fatal respiratory disease in anyone, including healthy adults. Fortunately, Ad 14 infections are uncommon and most infections from Ad14 strains are not serious; the severe or fatal outcomes from Ad14 are relatively rare. However, the appellation of "killer cold virus" has stuck with the Ad14 strain of Adenovirus. This virus was first identified in the 1950s when Adenoviruses were first isolated from human adenoids (Adenovirus named after adenoids). The number 14 of Ad14 represents the antigenic makeup of the strain; currently, there are at least 52 strains (antigenically distinct) that are distinguished by immunologic techniques. These viruses have a double-stranded DNA that is easily modified in lab experiments and apparently can undergo changes in the environment that may change Ad14's ability to infect cells and cause disease. The Ad14 strain is infrequently reported or encountered, while Ad4 and Ad7 strains are the most widespread Adenovirus strains (account for about 80% of adenoviral infections).
What are symptoms and signs of an Adenovirus 14 infection?
Adenovirus 14 infections usually begin with cold symptoms such as a cough, "runny nose," and mild fever and possibly throat irritation. The majority of infected people have these symptoms for several days (about three to five days), and then the infection clears without any medical treatment. However, with some individuals, infection with the adenovirus 14 strain (and rarely a few other strains such as 3, 7, 21, 30) progresses past the three to five days, causing additional symptoms. These symptoms may include diarrhea, bronchitis, eye infections, bladder infection, rash, high fevers, pneumonia, and shortness of breath (dyspnea). Although infection with Ad14 has been found in a few isolated individuals, most recent outbreaks have occurred with groups of individuals living in close contact. For example, the 2007 outbreak occurred in a military installation in San Antonio, TX, while the 2008 outbreak was in a small community in Alaska. A group of individuals that appears very ill (require hospitalization) due to respiratory problems, and are likely due to a "virus," should make clinicians suspect Ad14 as a possible cause of infection.
What causes an infection with Adenovirus 14 (Ad14)?
Usually, an individual becomes infected with Ad14 through person-to-person exposure via droplets containing Ad14 expelled by an infected person who coughs or sneezes. When these droplets reach the eyes, nose, or mouth, the Ad14 virus can attach and infect cells. These infected sites allow the virus to proliferate in some patients, and the virus then may go on to infect other organ systems, especially the lungs. Ad14 also can be passed through direct hand-to-hand contact if an infected patient has not washed their hands after coughing or sneezing. Adenoviruses can survive for days on objects like doorknobs, hand rails, and other objects. If a non-infected person touches the contaminated item, they can pick up the virus and then transfer it to a site (mouth, nose, eyes) where the virus can infect cells and proliferate.
How is an Adenovirus 14 infection diagnosed?
Diagnosis begins with a complete medical history and physical exam, especially noting if the patient has been associated with any group of people that has similar symptoms. Ad14 is one of several possible causative agents for an outbreak of respiratory problems in members of a group, like military recruits. To provide a definitive diagnosis of Ad14, blood, tissue, and/or exudates can be specifically cultured for the virus. Rising serum titers of antibodies toAd14, immunofluorescence tests for virus antigens in tissues, and a polymerase chain reaction (PCR) are also considered tests that provide a definitive diagnosis. However, in the vast majority of infected patients, such specific testing is not done and is not clinically necessary. It does not alter the management of the infected person. Electron microscopy shows the virus structure (Figure 1) but does not identify the strain. Supportive tests may include chest X-rays and blood tests and others that the physician deems appropriate.
What is the treatment for an Adenovirus 14 (Ad14) infection?
Treatment for Ad14 infection in most people consists of supportive care (rest, fluids, and fever reduction) because many people do well and have no problems. However, the Ad14 infections that progress require more intensive care; about 40% have required hospitalization in some outbreaks and some require respiratory assistance (intubation or mechanical breathing support) and intensive care. Mortality (death) rate has been as high as 5% in some settings. There are many reports of use of antivirals in severe Ad14 infections, but there are no good studies that support specific antivirals. Some benefits of antivirals such as ribavirin (Rebetol, Copegus) and cidofovir (Vistide) have been documented in ill patients; in severe cases, clinicians may try such agents because there is no other treatment other than supportive care. The effectiveness of antiviral medications has not been well studied in Ad14 infections. Consultation with an infectious disease, pulmonary, or ophthalmologist consultant, depending where the severe infection is located, is advised.
What are complications of an Adenovirus 14 infection?
What is the prognosis for an Adenovirus 14 (Ad14) infection?
In general, the prognosis for the majority (about 60% in some outbreaks) of people diagnosed with Ad14 is excellent with no complications. The prognosis declines as the severity of disease increases. Some people who are hospitalized may do well; those with other health problems or who are immunosupressed have a prognosis that may range from fair to poor depending on the individual's response to supportive and other possible (antiviral) therapies. Depending on the population and the setting, up to 5% of people identified as having Ad14 may die.
Can an Adenovirus 14 infection be prevented?
The only Adenovirus vaccines are against Ad4 and Ad7 and are not available to the general public, but are restricted to the military in the U.S. Currently, there is no commercially available vaccine against Ad14. Fortunately, the number of people infected with this strain has been very low, and to date, there is no good evidence this strain will rapidly cause global problems like HIV or Enterovirus strains. However, because this virus can be deadly and can be transmitted from person to person by droplets, it has the potential to become widespread. Also, there can be some confusion in the medical literature about Adenovirus "vaccines" as the virus has been used as a genetic carrier for other viral genomic elements to make research vaccines against other viruses; these should be listed as recombinant vaccines and not confused with the limited production of Ad4 and Ad7 vaccines.Good hand washing techniques, avoiding close contact with infected people, and avoidance of touching people or potentially contaminated surfaces and then touching eyes, nose, or mouth are some of the best ways to reduce the chance of getting infected with Ad14. These techniques are used to help avoid many other viral illnesses such as influenza, RSV, and other Enteroviruses. Patients with the disease should always cover their cough or sneeze and avoid touching others. Potentially contaminated items such as food, plates, utensils, and other handled items should be discarded or cleaned carefully before reuse to help reduce Ad14 transfer to others.
Where can people get more information about the killer cold virus (Adenovirus 14)?
The following sites may provide additional information about Ad14:
"Outbreak of Adenovirus 14 Respiratory Illness -- Prince of Wales Island, Alaska, 2008," Centers for Disease Control and Prevention
"Structure and Classification of Viruses," Medical MicrobiologyMedically reviewed by Robert Cox, MD; American Board of Internal Medicine with subspecialty in Infectious Disease
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