Dengue Virus

Dengue virus (DENV) is a small, positive-sense, single-stranded RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure virus of the genus Flavivirus. The infection can be transmitted to humans by the bite of female Aedes mosquitoes. The majority of infections are asymptomatic. Symptomatic individuals may progress through 3 stages of the disease, with severe manifestations occurring in those with previous infections. The febrile phase includes a high fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, headache and retro-orbital pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, severe myalgias and arthralgias (“breakbone” pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain), and macular or maculopapular rash. The critical phase includes more-severe manifestations of capillary leakage, hemorrhage, and shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock. A resolution of signs and symptoms occurs in the convalescent phase. The diagnosis is made based on the clinical history, examination, serology, antigen testing, or PCR. Management is supportive.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Classification

Rna viruses flowchart classification

RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure virus identification:
Viruses can be classified in many ways. Most viruses, however, will have a genome formed by either DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure or RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure. RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure genome viruses can be further characterized by either a single- or double-stranded RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure. “Enveloped” viruses are covered by a thin coat of cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane (usually taken from the host cell). If the coat is absent, the viruses are called “naked” viruses. Viruses with single-stranded genomes are “positive-sense” viruses if the genome is directly employed as messenger RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure (mRNA), which is translated into proteins. “Negative-sense,” single-stranded viruses employ RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure dependent RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure polymerase, a viral enzyme, to transcribe their genome into messenger RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure.

Image by Lecturio. License: CC BY-NC-SA 4.0

General Characteristics and Epidemiology

Basic features of dengue virus (DENV)

  • Taxonomy:
    • Family: Flaviviridae
    • Genus: Flavivirus
  • RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure virus
    • Single stranded
    • Positive sense
    • Linear
  • Spherical
  • Icosahedral symmetry
  • Enveloped
  • Size: 40–60 nm
Dengue fever virus particles flaviviridae

Transmission electron microscopic image of a tissue specimen depicts a number of round dengue virus (DENV) particles.

Image: “Transmission electron microscopic image of a tissue specimen depicts a number of round, dengue virus particles.” by CDC. License: Public Domain

Clinically relevant species

Four distinct serotypes (DENV 1–4) cause dengue infection.

Epidemiology

  • The leading cause of arthropod-borne viral disease in the world
  • > 100 million humans affected annually
  • The incidence is increasing.
  • Found in > 100 countries
  • Mortality:
    • Causes 20,000–25,000 deaths annually (primarily in children)
    • Untreated severe dengue fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever: 10% to 20%
    • Treated severe dengue fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever: 1%
  • Geographic distribution:
    • Southeast Asia
    • Australia and Oceania
    • Central and South America
    • Caribbean
    • Africa
    • Middle East

Pathogenesis

Reservoir

  • Humans (primary reservoir)
  • Primates

Transmission

  • Vector: female Aedes mosquitoes (primary mode of transmission)
  • Rare:
    • Vertical
    • Blood transfusions
    • Breast milk
    • Organ transplantation Organ Transplantation Transplantation is a procedure that involves the removal of an organ or living tissue and placing it into a different part of the body or into a different person. Organ transplantations have become the therapeutic option of choice for many individuals with end-stage organ failure. Organ Transplantation

Host risk factors

  • For dengue infection:
    • Living in an endemic area
    • Travel to an endemic region
  • For severe disease:
    • Previous dengue infection with a different serotype
    • Young children

Viral replication cycle

  • Virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview attaches to receptors on a cell’s surface → endocytosis
  • Acidification of endosome → fusion of cell and viral membranes → viral RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure released into cytoplasm
  • Translation Translation Translation is the process of synthesizing a protein from a messenger RNA (mRNA) transcript. This process is divided into three primary stages: initiation, elongation, and termination. Translation is catalyzed by structures known as ribosomes, which are large complexes of proteins and ribosomal RNA (rRNA). Stages and Regulation of Translation of RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure into viral proteins
  • Assembly and budding of new virions (mechanism is poorly understood)

Pathophysiology

  • Mosquito bite → subcutaneous injection of DENV into a human
  • Replication occurs in local cells (target cells not yet identified, but potentially macrophages and dendritic cells)
  • Spread to lymphatic system → viremia → dissemination to organs
  • Innate and adaptive immune response

Clinical Presentation

The majority of patients will be asymptomatic. Those with symptomatic disease may experience 3 phases: febrile, critical, and convalescent.

Febrile phase

This phase occurs after an incubation period of 3–14 days and lasts 2–7 days.

  • General:
    • Sudden high fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy
  • Pain:
    • Headache
    • Retro-orbital pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Lumbar back pain Back pain Back pain is a common complaint among the general population and is mostly self-limiting. Back pain can be classified as acute, subacute, or chronic depending on the duration of symptoms. The wide variety of potential etiologies include degenerative, mechanical, malignant, infectious, rheumatologic, and extraspinal causes. Back Pain
    • Severe myalgias and arthralgias (“breakbone” pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain)
  • Rash: 
    • Transient
    • Macular or maculopapular
    • May be pruritic
    • Distribution:
      • Face
      • Thorax
      • Abdomen
      • Extremities
  • Respiratory:
    • Pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis
    • Cough
    • Nasal congestion
  • Abdominal:
    • Nausea and vomiting
    • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Hepatomegaly

Critical phase

This phase is not seen in all cases and usually presents in patients who have had a previous dengue infection.

General features:

  • ↓ Fever 
  • Systemic capillary leakage
    • Edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
    • Ascites Ascites Ascites is the pathologic accumulation of fluid within the peritoneal cavity that occurs due to an osmotic and/or hydrostatic pressure imbalance secondary to portal hypertension (cirrhosis, heart failure) or non-portal hypertension (hypoalbuminemia, malignancy, infection). Ascites
    • Pleural effusion Pleural Effusion Pleural effusion refers to the accumulation of fluid between the layers of the parietal and visceral pleura. Common causes of this condition include infection, malignancy, autoimmune disorders, or volume overload. Clinical manifestations include chest pain, cough, and dyspnea. Pleural Effusion

Dengue hemorrhagic fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever:

  • Petechiae, purpura, or ecchymosis 
  • Mucosal bleeding
  • Hematemesis or melena
  • Heavy menstrual bleeding
  • Disseminated intravascular coagulation Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation ( DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation)
  • Abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Altered mental status

Dengue shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock syndrome:

  • Shock
  • Organ dysfunction 
  • Can be lethal
Bilateral periorbital ecchymosis dengue virus flaviviridae

Bilateral periorbital ecchymosis in a patient with dengue hemorrhagic fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever

Image: “Bilateral periorbital ecchymosis in a case with dengue fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever” by Kumar V et al. License: CC BY 2.0

Convalescent phase

  • Gradual resorption of extravascular fluid
  • Stabilization of vital signs
  • Resolution of hemorrhage
  • Pruritic, confluent erythematous rash may occur
  • Profound fatigue (may last from days to weeks)

Diagnosis and Management

Diagnosis

The diagnosis should be suspected in people living in or traveling from endemic areas. 

  • Confirmatory lab tests include:
    • Serology (ELISA)
    • Viral antigen detection
    • PCR for viral RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure
    • Viral culture (rarely useful)
  • Supporting evaluation:
    • Leukopenia
    • Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes
    • ↑ PT and PTT
    • ↓ Fibrinogen
    • Ultrasound → ascites
    • X-ray → pleural effusion

Management

There is no effective antiviral therapy, so management is supportive. This may include:

  • Rehydration
  • Blood transfusions (as needed)
  • Analgesia (avoid NSAIDs due to bleeding risk)

Prevention

  • Prevent mosquito bites
    • Insecticide/repellents
    • Protective clothing
    • Sleeping under a mosquito net
    • Eliminating stagnant water around the home
  • Vaccine Vaccine A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. Vaccination
    • Decreases the risk of severe disease in previously infected patients
    • Can increase the risk of severe disease in seronegative children
    • Not approved for travelers to endemic regions

Comparison of Similar Flavivirus Species

Table: Comparison of Flavivirus species
Organism Yellow fever virus Yellow Fever Virus Yellow fever is a disease caused by the yellow fever virus, a single-stranded, positive-sense RNA virus of the genus Flavivirus. Humans and primates serve as reservoirs, and transmission occurs from the bite of an infected female mosquito. Most patients present with fever and flu-like symptoms. Yellow Fever Virus Hepatitis C virus Hepatitis C Virus Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). Hepatitis C virus is an RNA virus and a member of the genus Hepacivirus and the family Flaviviridae. The infection can be transmitted through infectious blood or body fluids and may be transmitted during childbirth or through IV drug use or sexual intercourse. Hepatitis C Virus ( HCV HCV Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). Hepatitis C virus is an RNA virus and a member of the genus Hepacivirus and the family Flaviviridae. The infection can be transmitted through infectious blood or body fluids and may be transmitted during childbirth or through IV drug use or sexual intercourse. Hepatitis C Virus) Dengue virus (DENV)
Characteristics
  • 1 serotype
  • 40–60 nm
  • 2 serotypes
  • 55–65 nm
  • 4 serotypes
  • 40–60 nm
Transmission Mosquito Blood-borne Mosquito
Clinical presentation
  • Fever
  • Flu-like symptoms
  • Jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice
  • Multiorgan dysfunction
  • Hemorrhage
  • Shock
  • Asymptomatic
  • Hepatitis
  • Cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis
  • Hepatocellular carcinoma Hepatocellular carcinoma Hepatocellular carcinoma (HCC) typically arises in a chronically diseased or cirrhotic liver and is the most common primary liver cancer. Diagnosis may include ultrasound, CT, MRI, biopsy (if inconclusive imaging), and/or biomarkers. Hepatocellular Carcinoma (HCC) and Liver Metastases
  • Fever
  • Flu-like symptoms
  • Skin flushing/rash
  • Severe pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Multiorgan dysfunction
  • Hemorrhage
  • Shock
Diagnosis
  • Serology
  • PCR
  • Viral culture
  • Serology
  • PCR
  • Serology
  • PCR
  • Antigen testing
Management Supportive Direct-acting antivirals Supportive
Prevention
  • Mosquito-avoidance measures
  • Vaccine Vaccine A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. Vaccination
  • Avoid sharing needles.
  • Proper sharps and waste disposal
  • Testing donated blood
  • Mosquito-avoidance measures
  • Vaccine Vaccine A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. Vaccination

Differential Diagnosis

  • Zika Zika Zika virus belongs to the genus Flavivirus and is primarily transmitted by Aedes aegypti mosquitoes, but can also be transmitted sexually and transplacentally. Although most infected patients are asymptomatic, some may present with low-grade fever, pruritic rash, and conjunctivitis. Zika Virus Infection virus: a Flavivirus that causes fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis, and headache. An infection during pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care can result in microcephaly and developmental impairments in newborns. Diagnosis is established with serology or PCR. Management is supportive.
  • Chikungunya virus Chikungunya Virus Chikungunya virus belongs to the Alphavirus genus and causes a viral infection characterized by fever and joint pain. The arthropod-borne (arbovirus) virus is transmitted by mosquitoes (commonly Aedes albopictus and Aedes aegypti). Chikungunya Virus: a virus belonging to the family Togaviridae and transmitted by Aedes mosquitoes. Patients present with abrupt onset of fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and myalgias. A symmetrical, bilateral polyarthralgia can occur in distal joints, as well as a generalized maculopapular rash. Diagnosis includes serology and PCR. Management is supportive.
  • Malaria Malaria Malaria is an infectious parasitic disease affecting humans and other animals. Most commonly transmitted via the bite of a female Anopheles mosquito infected with microorganisms of the Plasmodium genus. Patients present with fever, chills, myalgia, headache, and diaphoresis. Malaria: mosquito-borne infectious disease caused by Plasmodium species. Malaria Malaria Malaria is an infectious parasitic disease affecting humans and other animals. Most commonly transmitted via the bite of a female Anopheles mosquito infected with microorganisms of the Plasmodium genus. Patients present with fever, chills, myalgia, headache, and diaphoresis. Malaria often presents with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, rigors, diaphoresis, jaundice, abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, hemolytic anemia Hemolytic Anemia Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia, hepatosplenomegaly, and renal impairment. A blood smear shows a single pleomorphic ring. Rapid testing for Plasmodium antigens can also be performed. Management requires a prolonged course of multiple antimalarial drugs Antimalarial drugs Malaria, a vector-borne parasitic disease caused by Plasmodium spp., is transmitted via injection of sporozoites or immature forms of the parasite into a person's bloodstream. Sporozoites then infect the hepatocytes and differentiate into schizonts, which subsequently rupture, and merozoites invade red blood cells. Antimalarial Drugs.
  • Leptospirosis Leptospirosis Leptospira is a spiral or question mark-shaped, gram-negative spirochete with hook-shaped ends. The major clinical species is Leptospira interrogans, which causes a mild flu-like illness in a majority of cases. The manifestations are biphasic, with Leptospira found in the blood initially. Leptospira/Leptospirosis: a disease caused by the gram-negative spirochete Spirochete Treponema is a gram-negative, microaerophilic spirochete. Owing to its very thin structure, it is not easily seen on Gram stain, but can be visualized using dark-field microscopy. This spirochete contains endoflagella, which allow for a characteristic corkscrew movement. Treponema Leptospira Leptospira Leptospira is a spiral or question mark-shaped, gram-negative spirochete with hook-shaped ends. The disease, leptospirosis, is a zoonosis, infecting animals. Rodents are the most important reservoir. Bacteria shed in the urine of rodents and other animals can be transmitted to humans via contaminated water. Leptospira/Leptospirosis. Bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview shed in the urine of rodents and other animals can be transmitted to humans via contaminated water. A mild flu-like illness occurs in a majority of cases. In a minority of patients, icterohemorrhagic leptospirosis develops, manifesting as hemorrhage, renal failure, and jaundice. A bacterial culture takes weeks, so other diagnostic tests Diagnostic tests Diagnostic tests are important aspects in making a diagnosis. Some of the most important epidemiological values of diagnostic tests include sensitivity and specificity, false positives and false negatives, positive and negative predictive values, likelihood ratios, and pre-test and post-test probabilities. Epidemiological Values of Diagnostic Tests, such as serology and dark-field microscopy, are used. Treatment is primarily with penicillin.

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