Yes, there is. And most of us already know the one word magic answer: spyware.
The Various Ways
Spyware is the only efficient way to track anyone’s Viber messages. One must be clear on this point that tracking anyone without their consent is illegal, unless you are a parent or a guardian and can prove to the court that whatever you did was in the best interests of your kid. The other way is to secretly open the target phone every now and then, and let’s face it: even Sherlock will not be able to pull that secret stunt for long.
For those who are new to the spyware world, this is a world of softwares that has the capability of gathering every tiny piece of information about a communication application and transferring it to another device for another person to read. This, however, does not imply breaching the laws of security and privacy for the other person, or the person using the application. Viber spyware tools should, by law, be used by parents or with consent, or else to track down your own deleted messages if the need arises.
There are many such tools. All of them are available online and a huge majority of them are free.
How does this Function?
What you do is to install the application on your phone and the target phone and possibly your own laptop as well. Next you launch the tool on all these devices. Now, whenever you want to, you can open up the Viber tab in the window of the spyware and receive minute by minute updates of all messages and the content shared via those messages, including the ones that get deleted.
This all sounds fun, right? However, just to be clear, no spyware is created to be used for leisure and satisfying your curiosities. Courts are still active. Just saying.