Covid -ve person forced/insisted to ask to office and get +v

you can send the covid test certificate  to your office by email. If the company again forcing then send a representation to health department of the state  by email 

Hi Sankar

My question was bit different,  Initially employee is COVID -ve but he/she still prefers to work from home because of High risk of getting infected.

Being COVID -ve, Office is insisting to come to the office. And candidate is going to office for less than 5 days. And he got infected.

After employee is COVID +ve office is not insisting and asking to stay at home.

yes I modified my answer already 
any how  if  the management  is ask you to work from office then you have to obey it .  Based on the ruling of  Government   Every company shall run the office with the strength of 50% workers. Therefore, the worker should accept the management demand.

The circumstances under which your Company asked you to be physically present. No Company shall insist its Employees attend Office if there was no dire necessity. Therefore, having been called upon to attend the Company in person, if such person contracts Corona, the Company needs to pay for the treatment as per their internal policy, which your Company is ready to comply with. Whether you can challenge the Company's decision calling upon you to be present in the Office depends upon the internal policy of 50% attendance on rotation. If the Company has certain duties (for example Banks) which cannot be performed from Home and certain duties which can be performed from home, such Company may rotate the staff between work from Home and Work from Office depending upon the requirement.

The facts posted do not suggest any wrongdoing or lapse on the part of the employer.

It is the policy and requirement of employer to decide, whether asking employee(s) to attend duty physically or WFH.

There is no harm or legal infirmity in the company asking you to attend the office is your test results state that you are covid negative.

If you contracted the disease subsequently after 5 days of working in the company, how can the company be held responsible for this.

The company has immediately passed instructions to you to work for home since you have been tested positive for covid.

You can contract the disease even if you were working from home because in the current situation anything is possible hence you cannot sue the company for any issue because the company is not at fault by asking you to attend the office physically when you have been reported to be fit enough to work from office. 

Do not complicate the things and get into more trouble besides the current troubles.