How do you find a virus that’s completely unknown?

A new study by a team of microbiologists and pulmonologists says look to the genome.

Viruses, the most abundant biological entities on Earth, are a scourge on humanity, causing both chronic infections and global pandemics that can kill millions. Yet, the true extent of viruses that infect humans remains completely unknown. Some newly discovered viruses are recognized because of the sudden appearance of a new disease, such as SARS in 2003, or even HIV/AIDS in the early 1980s.

1. Analyze the human lung virome 2. Identify divergent family of circular DNA viruses 3. Scan 7,000+ metagenomic samples; second most common DNA virus in human oro-respiratory tract. 4. Enriched in periodontitis and elevated in critical illness
(Image: Penn Medicine News)

New techniques now enable scientists to identify viruses by directly studying RNA or DNA sequences in genetic material associated with humans, enabling detection of whole populations of viruses, including those that may not cause acutely recognizable diseases. However, identifying novel types of viruses is difficult as their genetic sequences may have little in common with already known viral genomes that are available in reference databases.

Researchers at the Perelman School of Medicine have identified a previously unknown viral family, which turns out to be the second-most common DNA virus in human lung and mouth specimens, where it is associated with severe critical illness and gum disease, respectively. The team published their findings in Cell Host & Microbe. Senior authors Frederic D. Bushman, chair of the Department of Microbiology, and Ronald G. Collman, a professor of pulmonary, allergy and critical care, led the team that discovered this new virus, which they dubbed Redondoviridae.

“New sequencing techniques have helped us uncover a world of new viruses,” says Bushman. “However, the majority of the sequence data we have so far remains unclassified, leaving us much work to do in order to better understand the human virome and how these new species may be associated with illness.”

Read more at Penn Medicine News.