If you're looking for manga similar to Emerging, you might like these titles. All recommendations are made by Anime-Planet users like you!
A gruesome, disfigured, naked man climbs from beneath a manhole and wanders the streets briefly before vomiting blood and falling down dead. Detectives Nao and Ken are sent to investigate the case, but what they uncover is far more horrifying than they could possibly have imagined. What could have been a simple parasitic infection could have widespread, deadly consequences, and it's up to the duo to discover the truth behind these events...
Emerging and Manhole start out IDENTICALLY - gross dude wanders out and explodes on someone. The similarities in plot end there, with Manhole being more schemey and Emerging being straight horror/suspense, and admittedly I liked Emerging WAY more. Still, the biological horror and overall feel makes these a good rec for each other.
If you liked Emerging, you will also like Manhole, because both manga focus on a spreading disease in Japan. Manhole is much darker than Emerging.
Okinawa was the first affected; swarms of fish with spindly legs rose from the sea, carrying with them an overpowering stench of death. Kaori and Tadashi find themselves in the midst of the incident and quickly travel to Tokyo to ask for Tadashi's scientist uncle's help - but even Tokyo isn't safe for long, and sea creatures aren't the only beings affected by the horror...
Gyo is way more farfetched than Emerging, but both approach biological horror in a gripping way and are great reads.
I highly recommend Emerging and Gyo since both of these mangas contain lot's of gore and can entertain its readers greatly that'll make you want more.
Theme of both manga are similar, it is race against time to find a way to treat some terrible, fast spreading and deadly pandemic that is threating all of Japan, and maybe all of human kind. Setting of characters are also similar, but except of the main character, the survival of other character are different (saying anything more will just be spoiler)