An adult male titi monkey and his infant, at the California National Primate Research Center in Davis, Calif., which might have harbored a new-to-science virus that infects and is contagious to both monkeys and humans. (c) Kathy West

Adenoviruses are nonenveloped (without an outer lipid bilayer) icosahedral viruses, characterized by a particular large size compared to other types of viruses. For years, scientists have thought that each adenovirus strain could infect only one species of animal, however, a recently published report shows how the same strain that infected and decimated a titi monkey colony, also spread to a human who was working in the lab with the monkeys.

“Now adenoviruses can be added to the list of pathogens that have the ability to cross species,” study researcher Charles Chiu, director of the viral diagnostics center at the University of California, San Francisco, said in a statement

The outbreak occurred in 2009, at one of the labs at California National Primate Research Center, at the University of California, Davis. A colony of titi monkeys suddenly became ill with the virus, resulting in the death of about a third of the 65 monkeys there. Only four of the 23 sick monkeys survived the illness.

At the same time, one of the reserachers working with the titi monkeys became also sick, stricking him with a four week lasting fever and cold. Two more people from the researcher’s family, who had never encountered the monkeys, also became sick, though their illness was milder and lasted only two weeks.

From monkey to man

Researchers then analyzed the monkey-killing virus to see what type it was. They found high levels of an, up until then, unknown adenovirus which they decided to name titi monkey adenovirus (TMAdV).

As further evidence supporting the researchers’ hyphothesis that the TMAdV anchors on humans as well, scientists found certain antibodies in the in two of the people possibly infected with TMAdV. The antibodies were developed by the infected’s immune system as a response.

The researchers suggest this could happen again with other viruses. “Our discovery of TMAdV, a novel adenovirus with the capacity to cross species barriers, highlights the need to monitor adenoviruses closely for outbreak or even pandemic potential,” they write in the July 14 issue of the journal PLoS Pathogens.

Not the original host

The strikingly high mortality rate in infected monkeys, has led researchers to believe that the titi monkeys weren’t the original hosts as they would’ve most certainly developed some immunity to virus. Instead, the virus is probably native to some other species.

“The virulence of TMAdV in healthy and apparently immuno-competent [with normal, healthy immune systems] titi monkeys (83 percent case fatality rate) is highly unusual for infections by adenovirus,” the researchers write. “The severity of TMAdV-related illness in affected titi monkeys suggests that this species of monkey may not be the natural host for the virus.”

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