His disease—short for Werner-His disease—is a bacterial infection transmitted by lice. It results in a high fever that typically lasts for five days, hence one of the condition's other names: five-day fever. The disease is also sometimes caused by a slightly different strain of bacteria transmitted by ticks. Individuals with His disease often go through cycles of fever, with fever persisting for five days, subsiding for a time, then flaring up again. Other symptoms include fatigue, rash, weight loss, and pain in the muscles and bones. Pain is often reported to be more severe in the shin bones, hence another name for the condition: shin bone fever. The infection is easily treated with a proper diagnosis, though recovery can take up to a couple of months.
The disease is caused by Bartonella quintana, also called Rochalimaea quintana, a bacteria harbored by body lice. The infection is not directly caused by lice bites, but by lice feces, which often finds its way into open lice-bite wounds. Ticks can also transmit the disease through a slightly different strain of bacteria called Bartonella henselae.
His disease was first noticed in World War I and was also a problem in World War II, when body lice were easily spread amongst soldiers in the trenches. As a result, the disease was originally called trench fever. During those wars, it's been estimated that the disease affected more than a million people.
Currently, the homeless population is most affected by the disease. The homeless often get it from living outdoors in unsanitary conditions and from poor hygiene. His disease among homeless populations is commonly referred to as urban trench fever. Studies have shown that alcoholism increases the risk of contracting the disease.
Treatment almost always results in a full recovery, with few cases resulting in long-term disabilities or death. It can, however, take some time for the bacteria to be fully treated. Doctors must first be sure that body lice carrying the bacteria are completely eradicated. Delousing may not be as simple as checking for lice in the hair; lice often hide out in clothing and other possessions carried close to the body.
After delousing, various antibiotics are commonly administered to treat the bacterial infection, such as gentamicin and azithromycin. In patients with HIV and AIDS, the disease can sometimes result in bacillary angiomatosis, a condition characterized by skin lesions. Bacillary angiomatosis is often treated with doxycyclin and erythromycin.