This is one of the rare circumstances in which a non-union, non-government employee might even have a right to be reinstated in his job, in addition to potentially having a monetary remedy for wrongful termination.
There is a legal duty to reinstate a food employee once that employee overcomes the illness pursuant to Texas Food Establishment Rules §228.37. Failure to do so could result in the revocation of the employer's license to operate his business, or in a violation that could count towards doing so together with other violations, and would also be a matter of public record.
The employee could also filed a complaint under the FDA Food Safety Modernization Act:
If the evidence supports an employee’s claim of retaliation, OSHA will
issue an order requiring the employer to, as appropriate, put the
employee back to work, pay lost wages, restore benefits, and other
possible relief. The exact requirements will depend on the facts of
the case. If the evidence does not support the employee’s claim, OSHA
will dismiss the complaint.
After OSHA issues a decision, the employer and/or the employee may
request a full hearing before an administrative law judge of the
Department of Labor. The administrative law judge’s decision may be
appealed to the Labor Department’s Administrative Review Board.
The employee may also file a complaint in federal court if the U.S. Department of Labor does not issue a final decision within certain time limits. Details on this provision can be found in OSHA’s regulations, at 29 CFR 1987.114.
@user6726 Also notes that under the common law of Texas, terminating someone solely for refusing to violate the law gives rise to an action for wrongful termination, citing Sabine Pilot Services, Inc. v. Hauck, 687 S.W.2d 733 (Tex. 1985) and a subsequent case.
A termination of employment for this reason would also constitute a termination that is not for good cause, so the employee would be entitled to unemployment benefits.