imply vs explain in a passage

I have a hard time telling what's the difference between using "implication" and "explanation" in the following passage:

Even fatal pathogens can achieve evolutionary success. One implication is that a pathogen's virulence is a function of its mode of transmission.

Even fatal pathogens can achieve evolutionary success. One explanation is that a pathogen's virulence is a function of its mode of transmission.

Would someone help explain how these terms change the meaning of the passage? Thank you very much.

Let's break this down into two propositions:

A. Fatal pathogens can achieve evolutionary success.
B. A pathogen's virulence is a function of its mode of transmission.

Your first example is

A. One implication is B.

It would be equivalent to write A implies B. Since A is true, B is true. Keep in mind that this use of "implication" that we find in scientific and academic writing is not the everyday meaning of "implication." It's a specific use case described by OED the following way:

c. Logic. A relationship between propositions such that the one implies the other; also, a proposition asserting such a relationship.

Your second example is

A. One explanation is B.

This means B explains A (maybe). B is one possible reason that A is true. This is in line with the everyday meaning of "explanation."

(Why is B only a possible reason? "One explanation is" idiomatically means: "There are several possible conditions B, C, D, ..., any of which if true would explain A.")

TLDR: In the first case, A causes B, and in the second, B causes A.

An explanation, in this sense, is a possible underlying cause of a phenomenon. For instance "The explanation for the car battery being flat was that the door had been left open and the interior light had been on all night."

On the other hand an implication is something that is derived from a phenomenon and should influence future actions. For instance "Leaving the car door open meant that the interior light had been on all night which flattened the battery. An implication that can be drawn from this is that we should be careful to close the doors properly to ensure that the light goes out,

In the case of your examples the first one derives information from observation and, by implication, suggests ways to deal with the threat. The second one, however, merely reports on a possible reason for the phenomenon