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==Overview==
==Overview==
The most common [[complication]] of Lassa fever is [[deafness]]. Various degrees of deafness occur in approximately one-third of cases, and in many cases [[hearing loss]] is permanent. [[Spontaneous abortion]] is another serious complication. Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, overall only about 1% of [[infection]]s with Lassa virus result in death. The death rates are particularly high for women (greater than 80%) in the [[third trimester]] of [[pregnancy]], and for [[fetus]]es, about 95% of which die in the uterus of infected pregnant mothers.
Following exposure, infected patients remain asymptomatic for approximately 3 to 21 days. The majority of patients experience no or mild clinical manifestations. Typically, patients first develop persistent [[high-grade fever]] and other non-specific signs and symptoms. If left untreated, the majority of cases self-resolve without intervention. However, in the minority of cases, clinical manifestations may progress to [[hemorrhage]], [[deafness]], [[abdominal pain|abdominal]]/[[chest pain]], [[pleural effusion|pleural]]/[[pericardial effusion|pericardial]] effusions and [[ascites]], and [[facial edema]]. Eventually, manifestations progress to include [[convulsions]], [[hypovolemic shock]], [[coma]], and eventually [[death]]. The most common complications of Lassa fever are [[deafness|neurosensory deafness]] and [[hepatitis|hepatic injury]], which may be a mild [[hepatitis]] or [[fulminant hepatic necrosis]]. Although prognosis of Lassa fever is generally good, development of complications, [[pregnancy]], [[infancy]], are associated with poorer prognosis and increased risk of death.
 
==Natural History==
==Natural History==
* Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. For the majority of Lassa fever virus infections (approximately 80%), symptoms are mild and are undiagnosed.  
===Incubation Period===
* Mild symptoms include slight fever, general malaise and weakness, and headache. In 20% of infected individuals, however, disease may progress to more serious symptoms including hemorrhaging (in gums, eyes, or nose, as examples), respiratory distress, repeated vomiting, facial swelling, pain in the chest, back, and abdomen, and shock.
*Infected patients remain asymptomatic for 3 to 21 days following exposure.<ref name="pmid15487592">{{cite journal| author=Günther S, Lenz O| title=Lassa virus. | journal=Crit Rev Clin Lab Sci | year= 2004 | volume= 41 | issue= 4 | pages= 339-90 | pmid=15487592 | doi=10.1080/10408360490497456 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15487592  }} </ref>
* Neurological problems have also been described, including hearing loss, tremors, and encephalitis. Death may occur within two weeks after symptom onset due to multi-organ failure.
 
===Development of Clinical Manifestations===
*The majority of patients experience no or mild symptoms. Only a minority (approximately 15-20%) of patients experience multiorgan dysfunction, and typically 5-15% of infected patients die of Lassa fever.
*Patients typically first develop persistent high-grade [[fever]] (39 °C to 41 °C) and other non-specific symptoms, such as [[muscle aches]], [[conjunctival injection]], [[headache]], [[sore throat]], [[nausea]], and [[vomiting]].
*If left untreated, the majority of patients self-resolve without any intervention.
*In a minority of cases, patients may develop worsening abdominal/chest pain, temporary/permanent deafness, facial edema, mucosal bleeding and hemorrhage, pulmonary edema, pleural/pericardial effusions or ascites, multi-organ failure, and shock.
*Prolonged and worsening symptoms are usually associated with worsening prognosis, typically resulting in convulsions, encephalitis, seizures, coma and finally death.  
 
*The following table demonstrates the 4 clinical stages of Lassa fever <SMALL>(adapted from McCarthy et al. 2002<ref name="pmid12296302">{{cite journal| author=McCarthy M| title=USA moves quickly to push biodefence research. | journal=Lancet | year= 2002 | volume= 360 | issue= 9335 | pages= 732 | pmid=12296302 | doi=10.1016/S0140-6736(02)09938-5 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12296302  }} </ref> and Richmond et al. 2003<ref name="pmid14644972">{{cite journal| author=Richmond JK, Baglole DJ| title=Lassa fever: epidemiology, clinical features, and social consequences. | journal=BMJ | year= 2003 | volume= 327 | issue= 7426 | pages= 1271-5 | pmid=14644972 | doi=10.1136/bmj.327.7426.1271 | pmc=PMC286250 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=14644972  }} </ref>)</SMALL>
{| style="border: 0px; font-size: 90%; margin: 3px;" align="center"
| align="center" style="background:#4479BA; width: 50px;" |{{fontcolor|#FFF|'''Stage'''}}
| align="center" style="background:#4479BA; width: 400px;" |{{fontcolor|#FFF|'''Typical Symptoms'''}}
| align="center" style="background:#4479BA; width: 80px;" |{{fontcolor|#FFF|'''Days Since Symptom-onset'''}}
|-
| style="padding: 5px 5px; background: #EBEBEB;" | Stage 1|| style="padding: 5px 5px; background: #EBEBEB;" |High-grade [[fever]] (39-41 °C), [[malaise]], [[weakness]] || style="padding: 5px 5px; background: #F2F2F2;" |day-1 to day-3
|-
| style="padding: 5px 5px; background: #EBEBEB;" | Stage 2|| style="padding: 5px 5px; background: #EBEBEB;" |[[Headache]], [[backache]], [[chest pain]], [[sore throat]] with exudation, [[abdominal pain]], [[diarrhea]], [[nausea]], [[vomiting]], [[hypotension]], [[anemia]], [[proteinuria]], [[conjunctivitis]]|| style="padding: 5px 5px; background: #F2F2F2;" |day-4 to day-7
|-
| style="padding: 5px 5px; background: #EBEBEB;" | Stage 3|| style="padding: 5px 5px; background: #EBEBEB;" |[[Mucosal bleeding]], internal [[bleeding]], [[facial edema]], [[confusion]], [[disorientation]] and [[convulsion]]|| style="padding: 5px 5px; background: #F2F2F2;" |Beyond day-7
|-
| style="padding: 5px 5px; background: #EBEBEB;" | Stage 4|| style="padding: 5px 5px; background: #EBEBEB;" |[[Coma]], [[death]] || style="padding: 5px 5px; background: #F2F2F2;" |Beyond day-14
|}


==Complications==
==Complications==
* The most common complication of Lassa fever is [[deafness]]. Various degrees of deafness occur in approximately one-third of [[infections]], and in many cases hearing loss is permanent. As far as is known, severity of the disease does not affect this complication: deafness may develop in mild as well as in severe cases.
Complications of Lassa fever include the following:
* Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, only 1% of all Lassa virus infections result in death. The death rates for women in the third trimester of pregnancy are particularly high.  
*[[Sensorineural Deafness]]
* [[Spontaneous abortion]] is a serious complication of infection with an estimated 95% mortality in fetuses of infected pregnant mothers.
** The most common complication of Lassa fever is [[deafness]] (1/3 of patients)
** Deafness may be either temporary or permanent and may either by unilateral or bilateral.  
** Deafness does not seem to be associated with the severity of disease and may develop equally among patients with mild or severe infections.
*[[Spontaneous abortion]] among pregnant women
*[[Hepatitis]] and [[hepatic necrosis]]
*[[Splenic necrosis]]
*[[Adrenocortical necrosis]]
*[[Pulmonary alveolar edema]]
*[[Interstitial pneumonitis]]
*Lymph node [[histiocytosis]]
*Mucosal (e.g. GI) bleeding
*[[Renal tubular injury]] and [[interstitial nephritis]]
*[[Swollen baby syndrome]] (edema and bleeding among fetuses)


==Prognosis==
==Prognosis==
* Approximately 5-15% of patients hospitalized for Lassa fever die from the [[illness]]. The following factors are associated with poorer prognosis of Lassa fever:<ref name="CDC">{{cite web | title = The Centers for Disease Control and Prevention | url =http://www.cdc.gov/NCIDOD/dvrd/spb/mnpages/lassaslides.htm }}</ref>
** Infection during the t[[Third trimester of pregnancy|hird trimester of pregnancy]] or during [[infancy]]
** Increased [[viremia]] concentration
** Serum [[AST]] level > 150 IU/L
** [[Bleeding]], [[hypotension]], and [[shock]]
** Development of [[encephalitis]], [[confusion]], or [[coma]]
** [[Edema]] ([[facial edema]], [[Pleural effusion|pleural]]/[[pericardial effusion]], [[ascites]])


==References==
==References==
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[[Category:Tropical disease]]
[[Category:Tropical disease]]
[[Category:Biological weapons]]
[[Category:Biological weapons]]
[[Category:Infectious disease]]
 


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Latest revision as of 18:08, 18 September 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [2]

Overview

Following exposure, infected patients remain asymptomatic for approximately 3 to 21 days. The majority of patients experience no or mild clinical manifestations. Typically, patients first develop persistent high-grade fever and other non-specific signs and symptoms. If left untreated, the majority of cases self-resolve without intervention. However, in the minority of cases, clinical manifestations may progress to hemorrhage, deafness, abdominal/chest pain, pleural/pericardial effusions and ascites, and facial edema. Eventually, manifestations progress to include convulsions, hypovolemic shock, coma, and eventually death. The most common complications of Lassa fever are neurosensory deafness and hepatic injury, which may be a mild hepatitis or fulminant hepatic necrosis. Although prognosis of Lassa fever is generally good, development of complications, pregnancy, infancy, are associated with poorer prognosis and increased risk of death.

Natural History

Incubation Period

  • Infected patients remain asymptomatic for 3 to 21 days following exposure.[1]

Development of Clinical Manifestations

  • The majority of patients experience no or mild symptoms. Only a minority (approximately 15-20%) of patients experience multiorgan dysfunction, and typically 5-15% of infected patients die of Lassa fever.
  • Patients typically first develop persistent high-grade fever (39 °C to 41 °C) and other non-specific symptoms, such as muscle aches, conjunctival injection, headache, sore throat, nausea, and vomiting.
  • If left untreated, the majority of patients self-resolve without any intervention.
  • In a minority of cases, patients may develop worsening abdominal/chest pain, temporary/permanent deafness, facial edema, mucosal bleeding and hemorrhage, pulmonary edema, pleural/pericardial effusions or ascites, multi-organ failure, and shock.
  • Prolonged and worsening symptoms are usually associated with worsening prognosis, typically resulting in convulsions, encephalitis, seizures, coma and finally death.
  • The following table demonstrates the 4 clinical stages of Lassa fever (adapted from McCarthy et al. 2002[2] and Richmond et al. 2003[3])
Stage Typical Symptoms Days Since Symptom-onset
Stage 1 High-grade fever (39-41 °C), malaise, weakness day-1 to day-3
Stage 2 Headache, backache, chest pain, sore throat with exudation, abdominal pain, diarrhea, nausea, vomiting, hypotension, anemia, proteinuria, conjunctivitis day-4 to day-7
Stage 3 Mucosal bleeding, internal bleeding, facial edema, confusion, disorientation and convulsion Beyond day-7
Stage 4 Coma, death Beyond day-14

Complications

Complications of Lassa fever include the following:

Prognosis

References

  1. ↑ Günther S, Lenz O (2004). "Lassa virus". Crit Rev Clin Lab Sci. 41 (4): 339–90. doi:10.1080/10408360490497456. PMID 15487592.
  2. ↑ McCarthy M (2002). "USA moves quickly to push biodefence research". Lancet. 360 (9335): 732. doi:10.1016/S0140-6736(02)09938-5. PMID 12296302.
  3. ↑ Richmond JK, Baglole DJ (2003). "Lassa fever: epidemiology, clinical features, and social consequences". BMJ. 327 (7426): 1271–5. doi:10.1136/bmj.327.7426.1271. PMC 286250. PMID 14644972.
  4. ↑ "The Centers for Disease Control and Prevention".


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