Overview of human leptospirosis – guide for the public

Human leptospirosis can be a difficult infection to describe, as the symptoms can vary dramatically between patients. Some symptoms are extremely common, but only a small number of patients will experience the severe life-threatening illness known as Weil’s disease. The severity of the infection depends on the age and general health of the patient, plus the serovar (strain) of bacteria involved and the number of bacteria that entered the patient’s body.

The infection is usually systemic (affecting the whole body) and causes a sudden fever. In mild cases it lasts a few days, following a pattern similar to flu but often in two phases – a period of illness lasting a few days, then a slight recovery, then a second period of illness. In mild cases the second phase lasts a short time and the patient recovers, but in severe types the illness develops and progresses rapidly, leading to organ failure and often death if not treated with intervention and support.

Incubation time

From the time you were infected with the bacteria, there is a period where it has to reproduce enough to cause illness – called the ‘incubation time’. With human leptospirosis this is typically 3 to 21 days, with most patients developing illness after about 3 to 14 days. It does not usually take more than 28 days, but in rare cases very long incubation periods have been reported. It generally cannot show illness in less than 24 hours unless the volume of bacteria taken into the bloodstream was massively larger than normal.

First stage

Leptospirosis starts suddenly, with a severe headache, redness in the eyes, muscle pains, fatigue and nausea and a fever of 39°C (102°F) or above. There is sometimes a red non-blanching pinprick rash on the skin, similar to that seen in meningitis. Young children can be tired or distressed and may show an aversion to bright light. The severe headache is almost always present and can be incapacitating. Nausea may or may not cause vomiting. Muscle pains can be extreme and are often particularly bad in the calf and back areas – muscles will be sore to move and to touch. A rapid pulse is also common in the first few days.

The skin rash develops in the first one or two days and often the skin is warm and pink just beforehand, with the patient complaining of feeling warm. Rashes can occur anywhere but in some cases are confined to local regions of skin such as the front of the legs. Sometimes they will be itchy, but rashes are only seen in about 30% of all cases so the lack of any rash is not too significant.

Psychological changes are often seen, with patients feeling depressed, confused, aggressive and sometimes psychotic – with schizophrenia and hallucinations, personality changes and violence.

This phase lasts between three and five days, then the patient (temporarily) recovers. During this phase the bacteria are active in the patient’s bloodstream (so it is sometimes called the septecaemic phase) and so can be detected by lab tests.

Second stage

In many mild cases this doesn’t happen at all, but where the infection is more severe, the patient enters a second phase of illness after a few days of apprent recovery. The initial symptoms and fever return, accompanied with chest and abdominal pain, some renal problems and psychological changes. Increased symptoms of meningitis are often seen with neck stiffness and vomiting, but in most mild cases the patient will not suffer kidney or liver failure and will eventually recover. There may be a sore throat and dry cough, with a litle blood. With treatment, mild cases will recover within a few weeks.

During this second phase the bacteria are only really active in the tissues of the patient, and so can be difficult to find in the bloodstream, making lab tests a problem. This second phase is usually called the ’tissue’ or ‘immune’ phase.

Severe infections

In cases of particularly virulent serovars or patients with poor health, the infection follows a different pattern and the patient develops very rapid and severe symptoms from the start, without much of a remission. Symptoms are the same as for the mild type but more pronounced, and multiple organs are damaged – liver and kidney failure can occur within 10 days, leading to jaundice and death if not treated. Hemorrhages are common (including bleeding from the mouth, eyes and other mucous membranes), plus infection of the heart and significant internal bleeding. Dialysis is the most important intervention and the patient will require antibiotics and hospital admission in order to stand a chance of survival. Death, when it occurs, is usually due to heart, liver or respiratory failure. Severe infections are often called ‘icteric’ because of the presence of jaundice, and these are the only cases that can really be called Weil’s disease.


Patients with mild infections recover quite quickly, so are usually feeling OK after a few weeks, but they can suffer from fatigue and depression for a while and may be at risk from persistent infection. Patients with the more severe infections can take several weeks to recover, as removing the bacteria is not the problem – they will have caused damage to the body’s tissues that take time to heal. Although some patients can die, with medical treatment the chances of survival are good – though patients that have had a severe illness may suffer long-term symptoms due to organ damage that cannot completely heal. Psychological changes (mood swings, depression, psychoses) are common for a few months following recovery.


Patients that survive infection will develop some immunity, but only to the serovar that infected them and some closely-related ones. They can still be infected by other strains, and the immunity lasts no more than ten years in humans. There is a very small possibility of auto-immune reactions to the bacteria if patients are reinfected again, but the main concern of patients is that they can suffer from medium-term symptoms due to persisistent infection which are almost impossible to treat.