It started with a single monkey coming down with pneumonia at the California National Primate Research Center in Davis. Within weeks, 19 monkeys were dead and three humans were sick. Now, a new report confirms that the Davis outbreak was the first known case of an adenovirus jumping from monkeys to humans. The upside: the virus may one day be harnessed as a tool for gene therapy.
Adenoviruses are relatively large DNA viruses—as opposed to many other viruses that replicate using RNA—that commonly cause colds and respiratory infections in humans. They're also responsible for a variety of illnesses in cattle, dogs, horses, pigs, and other animals, but scientists thought the viruses and their ailments couldn't jump between species.
Then, on 14 May 2009, a healthy adult male titi monkey—a small, reddish-brown species that calls much of South America home—came down with a cough at the Davis primate center and soon became lethargic and wouldn't eat. Staff members gave the animal intravenous fluids and antibiotics, but its condition worsened, and after 5 days staff members euthanized him. Four weeks later, another titi monkey came down with the same symptoms. Then another. And another. Within 2 months, 23 of the 65-strong population had become sick, and 19 eventually died. A team led by infectious diseases researcher Charles Chiu of the University of California, San Francisco, analyzed lung tissue samples from the dead monkeys and identified a never-before-seen adenovirus, which they named titi monkey adenovirus (TMAdV).
But where did the virus come from? It's unlikely it originated in the titi monkeys themselves, Chiu says: "Hosts that are that susceptible to a disease are not likely to be its originators." So the researchers asked whether any lab workers had been sick during that period. One person, who had had close daily contact with the monkeys, reported coming down with a fever, chills, a headache, a dry cough, and a burning sensation in her lungs—hallmarks of the kinds of respiratory infection commonly caused by adenoviruses. Two of her family members reported similar, though less severe, symptoms in subsequent weeks.
Neither the lab worker nor her family members sought medical attention, and all recovered within 4 weeks, after which it was too late for researchers to swab for traces of the adenoviruses directly. Instead, they examined the patients' blood for antibodies and compared them with those found in the infected monkeys. The lab worker and one of her family members showed a match, suggesting that the monkeys gave the virus to the lab worker or vice versa. But when the team tested a representative set of 81 blood samples from donors in the western United States, none had antibodies. That suggests humans weren't the source of the outbreak either.
Friday, July 15, 2011