The phrase "after the first case" is correct and usable in written English.
It can be used to refer to a subsequent event or situation that follows the initial case being discussed.
Example: "The results were significantly different after the first case was analyzed."
Alternatives: "following the initial case" or "subsequent to the first case".
After the first case, the building's owner was fined.
In the weeks after the first case was confirmed, WHO deployed health workers for a "mop up" immunisation campaign, targeting children under the age of 15.
Early last week, McDonald's and other restaurant stocks fell after the first case of mad cow disease was found in the United States.
The government finally announced that it would buy up the beef from cows slaughtered in the month after the first case of mad cow disease.
More than 50 nations, including Japan and South Korea, shut their borders to American beef after the first case was found.
Japan banned all US beef imports in 2003 after the first case of mad cow disease was discovered in the United States.
After the first case of per-oral endoscopic myotomy (POEM) at our institution in 2008, the procedure was quickly accepted as an alternative to surgical myotomy and is now established as an excellent treatment option for achalasia.
The announcement comes two years after the first case in a small rural village in Guinea, 42 days after the last patient tested negative in Liberia and almost two months after the last case in Sierra Leone.
The outbreak of Lassa fever was only announced in January – months after the first case of the disease happened in August – with subsequent deaths reported in 10 states, including Abuja.
More than 50 members of the public could have been exposed to a rare viral infection, health officials fear after the first case of monkeypox was diagnosed in the UK.
At the height of the outbreak, the first few months after the first case was identified last February, all rights of way for walkers in the countryside were closed.
