Febris is the Roman Goddess of fevers, Who can bring or dispell sickness. She is the fever personified and Her name means just that: "Fever" or "Attack of Fever". She may have been especially a Goddess of Malaria, which was notoriously prevalent in ancient Italy, especially in the swampy regions as the disease is transmitted by mosquito, and She was given offerings by Her worshippers in the hopes of being cured. The classic symptoms of malaria include periods of fever, lasting from four to six hours, which come in cycles of every two to three days, depending on the specific variety of parasite; this would explain the odd phrase "attack of fever", as it was something that came and went, and would support Febris's links with that specific disease.
At any rate, malaria was all too common in ancient Rome, and the Romans knew it; they also had some idea what caused it and how to avoid it—Varro, writing in the first century BCE said that when building a house or farm "especial care should be taken to place it at the foot of a wooded hill where it is exposed to health-giving winds. Care should be taken where there are swamps in the neighbourhood, because certain tiny creatures which cannot be seen by the eyes breed there. These float through the air and enter the body by the mouth and nose and cause serious disease"—which is a pretty good guess considering that germs would not actually be seen by the human eye until some 1700 years later, when the Dutch scientist Antony van Leeuwenhoek "discovered" bacteria with an early form of microscope (incidentally he called the little buggers "animalcules"; and if you read his account, I guarantee you will want to immediately brush your teeth). The Romans were quite aware of good hygienic practices and incorporated them into their city planning and public works projects, for example by constructing great sewer systems to funnel waste away, by draining swamps any chance they got, and of course by building many many bathhouses.
Malaria was a serious threat to Rome and her people—recently the idea has been floated around that a particularly virulent form of the disease was a major contribution to the collapse of the Empire. Even today, malaria is one of the biggest killers of the communicable diseases, second only to tuberculosis, and there is currently no vaccine. Malaria is particularly deadly to pregnant women and very young children, and is known to cause stillbirths and miscarriages. Having healthy children is of course an especial concern of parents (and the state to some extent), and this probably explains why Febris had three shrines in Rome. At these shrines She was given offerings of amulets or charms, called remedia (just like it looks, meaning "remedies", or "cures") which had been worn by those who had been sick but had recovered.
Her most important shrine or altar was somewhere on the Palatine Hill; there is no trace of it left and its exact location isn't known. Another small temple or shrine to Febris was located on the Quirinal Hill, somewhere near the Baths of Diocletian on the Vicus Longus (literally, "Long Street"), near its highest point (which I suppose would be furthest away from the swamps). Her third shrine was located on the Sacra Via, the "Sacred Way", the oldest street in Rome, which connected the Forum with the Palatine Hill; it was situated on the slope of the Velia, the small hill between the Palatine and the Oppius (part of the Esquiline Hill), which would place it squarely between the Forum proper and the site of the Colosseum. The placement of Her shrine at that location may be a memory of the formerly swampy and pestilential character of the Forum valley before its marshes were drained.
Febris's cult was considered to be very ancient, which is not surprising, as fever and sickness has been around as long as humans have (malaria is even said to have been a strong influence on human evolution). Febris is known from inscriptions in other parts of the Empire, so Her cult was not local to Rome. She is sometimes said to be accompanied by Dea Tertiana and Dea Quartiana, the Goddesses of (malarial) tertian fever and quartan fever, so-named because the fever returned every third or fourth day. An inscription to Dea Tertiana has been found (though since lost) at the fort of Habitancum, in the modern town of Risingham in northern England, indicating that even in the cooler climates malaria was common and feared.
Several epithets of Juno are spelled quite similarly to Febris's name and have caused some confusion, to the point where the month of February was supposed to have gotten its name from the "fevers of love" which were explained as being peculiar to that month for some reason. These names—Februa, Februlis, Februata, Februtis, or Februalis were epithets of Juno as a childbirth Goddess Who delivers the afterbirth and then purifies the new mother; the name is related to februalis, "religious purification" and not to Febris's name.
Also called: Dea Febris