erwischen
to catch
To catch someone in the act of doing something forbidden or secret, or to apprehend them.
Die Lehrerin hat den Schüler beim Spicken erwischt.
The teacher caught the student cheating.

to catch
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to catch
To catch someone in the act of doing something forbidden or secret, or to apprehend them.
Die Lehrerin hat den Schüler beim Spicken erwischt.
The teacher caught the student cheating.

The verb 'erwischen' (to catch) has a rather colloquial character in all of its meanings. It is used more often in spoken language than in formal written texts.
Ich habe ihn gerade noch erwischt, bevor er zur Tür hinausging.
I caught him just before he went out the door.
When you catch someone doing something forbidden, you use the preposition 'bei' followed by a noun in the dative. Often a verb is nominalized in this construction.
Meine Mutter hat mich beim heimlichen Naschen erwischt.
My mother caught me secretly snacking.
A very common idiom is 'jemanden auf frischer Tat erwischen' (to catch someone red-handed). It means that you catch a person at the exact moment when they are doing something forbidden.
Die Polizei hat den Einbrecher auf frischer Tat erwischt.
The police caught the burglar red-handed.
In the meaning 'rechtzeitig erreichen' (to reach in time), 'erwischen' (to catch) is almost always used in connection with public transportation. Typical phrases are 'den Bus erwischen' (to catch the bus), 'den Zug erwischen' (to catch the train), or 'den Anschluss erwischen' (to make the connection).
Ich bin gerannt und habe den Zug in letzter Sekunde noch erwischt.
I ran and caught the train at the very last second.
The phrase 'eine Krankheit erwischen' (to catch an illness) is typical of everyday spoken language. For example, you can say 'eine Erkältung' (a cold), 'die Grippe' (the flu), or 'einen Virus erwischen' (to catch a virus).
Zieh dir eine Jacke an, damit du dir keine Erkältung erwischst.
Put on a jacket so you don't catch a cold.
to get / receive
'bekommen' and 'erwischen' can both be used for illnesses. 'bekommen' is neutral: you can get a fever, a cold, or a headache. 'erwischen' is more colloquial and often sounds as if the illness came suddenly or unpleasantly. For example, you say: 'Mich hat eine Grippe erwischt' (I've caught the flu). Learners may confuse the words because both fit in situations like this. If you want to speak factually, use 'bekommen'; if it should sound more casual and a bit more personal, 'erwischen' fits.

Im Winter erwischt meine Kollegin fast jedes Jahr eine Erkältung.
In winter, my colleague catches a cold almost every year.
Nach der langen Wanderung hat Yara starke Kopfschmerzen bekommen.
After the long hike, Yara got a bad headache.