Hiring agency worker as full-time member of staff

Limited contact from important employee off sick

I do not have a sickness policy in place for my employees at my business, only that if there is a first day of absence the employee must report in at 8.00am personally. Two weeks ago my employee who is the key holder to my business and is required to open up in the morning did not turn up. I received a call from a friend at 10:20am to say the employee would not be in that day when the business is supposed to open at 9:15am. I later received a call that day from the employee’s husband saying that she had been to the doctor's and had been diagnosed with a chest infection. This was the case for the next 2 days. Each time I requested to speak to my employee personally I would have to communicate with her husband, who on the 4th day informed me that my employee would be off for another week. What action can I take?