Hello picochun!
The brown bead-like structures you are observing are a type of scale insect that feed off of the orchid, not a sign of infection. However, scale infestations can lead to intense tissue damage and even transmission of disease in some cases. I am dealing with a similar issue right now and I really suggest that you follow two steps to mitigate and damage:
1) Apply insecticide. I usually take isopropyl alcohol of 70-90%, put it on a paper towel, and swab the areas with visible infection. The signs of scale you are witnessing seem to be the gestation stage, so you should also look out for smaller scale bugs in between leaf crevices. A q-tip and alcohol can help clean up the tough to reach places, and you can assess the scale population after each swab by looking for an orange to brown residue (the remains of the scale insects) on the q-tip or paper towel. This step should be completed every week for about 6-8 weeks (gestation period of brown soft scale) until you do not see any more signs of them. Additionally, alcohol and most insecticides should be applied at night as they increase leaf light sensitivity and the chance of sunburn.
2) Quarantine this orchid from the rest of your collection in a separate room. Scale spreads rapidly by crawling (I have had about 4 plants get infected from just 1 plant that was near all of them).
Hope this helps
let me know if you have any questions