Prognosis

In general, the prognosis in patients with mild disease is favourable; however, patients with severe disease often have a poor prognosis. Prognosis varies according to a number of factors, including a patient's immunological status and age. Other factors associated with a poor outcome include hypotension, oliguria, jaundice, hyperkalaemia, and an abnormal chest auscultation; all present on initial evaluation.[86][87][88] Cases in which chest radiographs detect air-space nodules have been associated with severe leptospirosis.[68]

One study found two factors independently predictive of development towards severe leptospirosis: clinical jaundice and cardiac damage seen either clinically or on ECG.[89] The median mortality rate of untreated leptospirosis was 2.2% in one systematic review, with a broad range of 0% to 39.7%.[73] During the immune phase, mortality varies between 5% and 40%.[2] Anicteric leptospirosis carries a mortality of less than 1%, whereas icteric leptospirosis (better known as Weil's disease), involving jaundice, haemorrhage, and acute renal failure, has a mortality rate of 5% to 15%.[50] Severe leptospirosis with pulmonary haemorrhage has a mortality rate of >50%.[50]

Death may occur secondary to cardiac arrhythmias, cardiac failure, or adrenal haemorrhage.

Populations at risk of severe disease

It is of particular relevance to mention that advanced age is associated with greater morbidity and mortality. In a systematic review that assessed the mortality of untreated leptospirosis, older patients aged >60 years had a mortality rate of 60%.[73] Older patients with Weil's disease have higher mortality.[5]

Pregnant patients can have different outcomes.[54] The fetus can acquire infection during the acute/initial phase through placental transmission; this presentation can lead to fetal death. In the absence of bacteraemia, the fetus and the mother can be at risk for morbidity and mortality if the mother experiences severe infection complications, such as high fever and haemodynamic disturbances.[55] Women are more likely to have a spontaneous abortion if leptospirosis occurs early in pregnancy.[11]

Recurrence

After a patient recovers from leptospirosis, they may become immune to re-infection by the same serovar or strain. Serovar-specific antibodies are thought to be protective as long as their concentration is high.[5]

Chronic leptospirosis (renal sequelae)

Limited data suggest that there may be an association between leptospirosis and chronic kidney disease, but larger studies are needed to confirm whether leptospirosis is a risk factor for chronic kidney disease.[90]

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