How Does Adenovirus Spread

Introduction

The Adenovirus (AdVs) belongs to the Adenoviridae family and is made up of over a hundred serotypes that can cause harm to the health of reptiles, birds, fish, mammals, and many other vertebrates. The International Committee on Taxonomy of Viruses database reports that the Adenoviridae family comprises five genera and 74 species. AdVs have been known to cause infections of the eyes, gastrointestinal tracts, respiratory tracts, and urinary tracts. These infections can be self-limiting and can last for many years and even result in the development of isolates of newer recombinant viruses! AdVs are highly contagious and can even lead to local epidemics. Additionally, immuno-compromised patients are more prone to being attacked by AdVs with consequential debilitating consequences to their health. Unfortunately, there are no definite curative medical therapies for AdVs at the moment.¹

The AdVs were first described at the beginning of the 1950s; however, there is still a paucity of data and insufficient understanding of the mechanisms by which they function in the infected cells with respect to the mode of interactions with host cells vis-a-vis host response to infection.²

Description and attributes of the adenovirus

The virus genome can be described as a double-stranded linear DNA and a terminal protein. The viral DNA has relationships with the very basic protein VII as well as small peptides (mu). A virus-encoded protease is also present, essential to processing structural proteins that are important in viral infection propagations. The AdVs target the nucleus of the cell with their genome and replicate actively. They have been considered gene delivery vehicles due to this replication efficacy.²

The AdV infection involves 2 processes, the first involves entry into the host calls and further delivery of its genome to the host nucleus. A selective transcription and further translation of the genes follow this. All these modulate cellular functions and aid further replication of viral DNA and more translation and transcription of the late genes. Thereafter, structural proteins assemble in the nucleus and further maturation of the virus. Viral cells are adsorbed into target host cells through specific cell receptors.²

Transmission of adenovirus

Studies have shown that effective handwashing techniques have been found to protect against the spread of AdVs; however, this alone is insufficient to curtail the spread of the disease. There are efforts underway to revive Adenovirus vaccine production which was quite common in the 1970s (but was lost in 1999) to control the endemic spread of the infection. Due to the advent and protection against bioterrorism, it is important to better understand the transmission mechanisms of the AdVs through serological testing and seroconversion rates, surveillance of the environment, and pathogen detection.³

The Human AdVs were first identified in human adenoids. Where there is the absence of effective treatment for the illness, they may have debilitating health consequences, particularly in people with weak immune systems. AdVs are found globally in dirt exposed to human waste and human sewage. They spread through air droplets from one individual to another, ingesting faecal matter and exposure via contaminated surfaces. AdVs have been found among organ transplant recipients. Additionally, AdVs are responsible for the development of hepatitis among children with compromised immune systems.

Some common symptomatic manifestations include fever, sore throat, tiredness, coughing, and even body pains. More life-threatening conditions may include acute respiratory stress syndrome, pneumonia, and even death! Sadly, there are no direct curative therapies for AdV infections. Usually, the aim of therapy is always to ease the manifested symptoms and provide support and palliative care for the patient- preferably in isolated areas to limit further transmissions. It is important to install timely precautions and measures to prevent the spread of AdVs. This is because they have the ability to affect even healthy individuals who do not normally come down with ailments. They pose grave consequences to global and community health as they have the capability to cause outbreaks and widespread epidemics if left unmanaged- similar to the coronavirus 2. When viruses manifest in a region of the world, they have the risk of spreading into neighbouring countries by being carried by travellers serving as human carriers, passing it on via human-to-human transmission. Thereby, increasing the burden on the already stretched-out healthcare systems of many parts of the world. It is important to strengthen preventive healthcare.⁴

Treatment modalities of adenovirus infections

Decisions about treatment choices to be administered to each immunocompromised patient vary. Essentially, this is influenced by each individual's peculiar risk circumstances and the available treatment options in the area. Antiviral prophylactic medications available against HAdV infections are not readily considered due to their toxicity and negligible efficacy, especially in immunocompromised individuals. It is worthy of note that the antivirals and immune therapy strategies currently available have not successfully overcome the fatal courses of AdV infections in immunocompromised patients. A virostatic agent used is cidofovir, and even though it is known for its toxic effect on the kidneys, others may include ganciclovir and ribavirin, which have minimal efficacy.⁵

Some researchers have drawn an association between AdV infection and some cases of acute hepatic failures; however, opinions differ on this. Adenoviruses are contagious and are known to result in respiratory tract infections usually. Few strains may target cells outside the respiratory tract- an example of this is the type 41 adenoviruses, which is strongly associated with hepatitis among children with lowered immunity. It is essential to consider all possible factors and investigate all likely infectious agents to reach a definite conclusion. Patients must be quarantined during diagnostic tests, investigations, and during treatments. Contaminated surfaces, blood, faeces, and bodily fluids must be decontaminated and treated by a multidisciplinary team to curtail the disease and prevent its spread.

Summary

The Adenovirus (AdVs) is a broad family of viruses with over 100 serotypes affecting many vertebrates, causing infections in the eyes, the respiratory tract, the gastrointestinal tract, and urinary tracts with grave consequences, especially in immunocompromised patients. Despite its discovery in the 1950s, there is still a greater understanding of their mechanism and interactions with the host cells. They are transmitted through air droplets from nasal airways, ingestion of faecal matter, or contaminated surfaces, posing a serious public health risk similar to Covid-19. Effective handwashing can mitigate its spread. There is ongoing research to revive the production of the AdV vaccines which were stopped in the 90s and explore treatment options even though the current antiviral therapies have shown limited efficacy and marked toxicity. Strengthening preventive healthcare measures is essential to mitigate the risk of Adenovirus outbreaks and their threatening impacts on global health systems.