Myalgia and fatigue after Ross River virus disease

Case Scenario

Diana was a slim, active, 64-year-old woman who had enjoyed excellent health throughout her life. While on a camping holiday in the northwest of Australia, her companion developed a severe viral illness that was subsequently diagnosed as Ross River fever. A week or so later, Diana developed similar symptoms with fevers, fatigue, joint pains and myalgia. She assumed that she too had Ross River fever and did not seek medical confirmation. Diana’s companion was completely recovered within one month.

A year later, Diana is still not well. She has daily muscle pains, a constant feeling of heaviness in her limbs and a residual profound fatigue that has a major impact on her usual activities. What has happened to her immune system?