The flu is a virus that attacks your immune system when you are sick. While the flu virus is attacking however you start to get the regular symptoms of getting sick such as a feaver, coughing, vomiting and other things. But the reason why those things happen is because that is the reaction your body is giving off while your immune system is fighting off the virus. Which is why those symptoms stop when you get better.
Geocentric - Earth Centered solar system
Heliocentric - Sun Centered solar system
It is a very interesting question - the technology is real and the research on eDNA published in a journal in 2017.
eDNA stands for enviornmental DMA sampling. It allows scientist to test water samples for the presence of the DNA of the invasive fish species. It is more effective than traditional methods of sampling because it does not require trapping or sighting of the invasive species. Water samples can be collected anywhere any time and the DNA results are as accurate and detailed as collected from the invasive species themselves. It provides a complete picture of what invasive species are there.