If you are travelling locally in a natural resort, you will need a certain level of protection. If the area is known to have any specific viruses or bacteria, you should know about them. Also if you are travelling abroad, it is better that you get the best filters that are available. It is better that one take more caution than less.
Type of Cleaning
There are filters that get rid of the bacteria but not the virus. Then there are purifiers that clean the water by not only getting rid of the bacteria but also viruses. The later is a better idea especially if you are travelling in an area with whose water conditions you are not familiar with.
The amount of water that can be cleaned at a given time should also be considered. If you drink a lot of water or are going to an area which will have a lot of heat and humidity, you will need something that can process greater volume at a given time. Also if you are travelling in a group, it is better to keep one that can deal with greater volume of water.
These water filters come in all shapes and sizes. It is best that the ones that are portable and easy to carry should be taken along. You do not want to be carrying something that is too large and difficult to move with. Check out all the options that are available to make sure that you pick the one that suits your needs.