It was a diagnostic challenge, and doctors began reviewing the list of possibilities that could match his condition. The first guess of pneumonia could explain some of his respiratory findings, but he didn’t have a cough, had tested negative for common respiratory pathogens, and the lung imaging didn’t quite fit, making it seem unlikely. Blood cancers, such as polycythemia vera, might be able to explain the high concentrations of blood cells. And it might also make him more vulnerable to opportunistic lung infections, like a fungal infection that could explain the halo sign. But blood cancers were also deemed unlikely given that he didn’t have enlarged organs, which is often seen with such conditions. Another possibility of pulmonary–renal syndrome, but that also didn’t line up with the man’s case.
Diagnosis
There was one other possibility that seemed to tick all the boxes: fever, gastrointestinal symptoms, low oxygen saturation, pulmonary edema, and shock—a hantavirus infection.
Hantaviruses are RNA viruses that infect rodents worldwide. They typically cause asymptomatic, chronic infections in the animals, which spread the virus widely into their environments through their urine, feces, and saliva. Humans get infected when virus particles from rodent-contaminated areas are stirred up into the air and inhaled, or through direct contact with the virus via the eyes, nose, mouth, or cuts.
In humans, the viral infection is anything but asymptomatic. While the disease mechanism isn’t entirely understood, the virus appears to be able to modulate immune responses in humans, causing blood vessels and capillaries in various places in the body to start leaking plasma. This leads to fluid building up in the lungs (the pulmonary edema) and systemic circulatory collapse.
A cardiopulmonary hantavirus infection typically has four stages: the incubation period, which can last up to 45 days after virus exposure; a prodromal phase up to 12 days that are marked by fever, fatigue, and pains; the cardiopulmonary phase, where breathing trouble, low oxygen saturation, and shock can develop; then, if you make it, the fourth stage, in which respiratory symptoms improve, but there’s lingering fatigue and the kidneys make abnormally large amounts of urine.
