You didn't say which country you work in, so let's take the US as an example:
- Do I have a right to have my medical information kept private in the workplace?
Your employer has a number of ways to obtain medical information about you, whether it's because you volunteer it when you call in sick or tell co-workers, or because you provide requested information on health insurance application or workers compensation claim forms. However, just because your employer has the information does not mean that it should be shared with everyone in the workplace, especially when you have not chosen to do so.
The basic legal principle that employers should follow is not to reveal medical information about you unless there is a legitimate business reason to do so. But because that standard is fairly vague, there are laws which more specifically protect the privacy of your medical records, such as the Americans with Disabilities Act, the law which makes it illegal to discriminate on the basis of an employee's disability. State laws may also provide additional protection.
From: Workplace Fairness (emphasis mine)
If you would like more reliable resources, I recommend the documents that WF refers to:
Or if you would prefer the European approach:
- Member States shall prohibit the processing of personal data revealing racial or ethnic origin, political opinions, religious or philosophical beliefs, trade-union membership, and the processing of data concerning health or sex life.
From: Directive 95/46/EC of the European Parliament and of the Council of 24 October 1995 on the protection of individuals with regard to the processing of personal data and on the free movement of such data (Article 8(1), emphasis mine)
Hence, the bottom line is that it is utterly irrelevant whether your coworker does or does not have an underlying medical condition that you don't know about, because people have the right to health information privacy worldwide. In other words: your coworker's potential medical condition is none of your business.
The right to privacy has been around for a while and as such should be understandable to any civilized human being. To be consistent with meeting health SE's reference requirements:
Privacy addresses the question of who has access to personal information and under what conditions. [...]
There are a variety of reasons for placing a high value on protecting the privacy, confidentiality, and security of health information (reviewed by Pritts, 2008). Some theorists depict privacy as a basic human good or right with intrinsic value (Fried, 1968; Moore, 2005; NRC, 2007a; Terry and Francis, 2007). They see privacy as being objectively valuable in itself, as an essential component of human well-being. They believe that respecting privacy (and autonomy) is a form of recognition of the attributes that give humans their moral uniqueness.
The more common view is that privacy is valuable because it facilitates or promotes other fundamental values, including ideals of personhood (Bloustein, 1967; Gavison, 1980; Post, 2001; Solove, 2006; Taylor, 1989; Westin, 1966) such as:
- Personal autonomy (the ability to make personal decisions)
- Dignity and worth as human beings
From: Beyond the HIPAA Privacy Rule: Enhancing Privacy, Improving Health Through Research..
Although the linked text refers to privacy of information of health research participants, the introductory part (Definitions, Importance of Privacy) is about the general principle.