Causing over 76,000 infection cases and 2,300 deaths in China alone, the source of the ongoing novel coronavirus outbreak is still a question that needs a clear answer. Coronaviruses are known to circulate in mammals and birds, and initial investigations said the virus could come from bats, but a recent research indicates that the virus was probably transmitted to humans by another animal. But, one should also know that it's not only animals that can pass on diseases to humans. Humans also carry and transmit diseases to animals. 

Here are some cases showing that reverse infection also needs to be in focus. 

Tuberculosis

According to an article from Medical News Today, in 2004, a paper described the case of a dog showing symptoms of reduced appetite, vomiting and cough. No cause could be found after an array of tests until the vet learned that the owner was being treated for tuberculosis (TB) for months. Having ruled out all other possible sources, the author concluded that the dog has contracted tuberculosis from its owner. This was the first documented human-to-animal transmitted TB case.

But it was not the only case.

Besides dogs, other animals were found affected by this human-borne TB, as several elephants also contracted TB from humans in the U.S.

Flu

The first case of H1N1 flu transmission from a human to a cat was documented in 2009. The indoor cat had no contact with other animals or humans rather than its owner, who had been taken to the hospital after having caught influenza.

In the following two years, researchers have found over 13 cases of human-to-animal transmitted H1N1 infection.

Respiratory illnesses

Due to genetic resemblance between humans and chimpanzees, many diseases that kill us are also fatal to them.

In 2003, 2005, and 2006 outbreaks of respiratory diseases struck wild chimpanzees at the Mahale Mountains National Park in Tanzania. Researchers had reached the end of their wits to find the cause before a human-related virus was identified, proving the fatal illness was transferred to them from staff who had caught a cold.

( All photos via VCG. )

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