Dengue Fever: Beyond the Tropics
Dengue Fever: Beyond the Tropics
Dengue fever develops from dengue virus infection following a mosquito bite. Although DHF can develop in patients with a first episode of dengue infection, it appears to be more likely following a second infection with a different serotype of dengue virus. A second viral exposure can result in more severe clinical infection, as preexisting antibodies bind to the virus to enhance viral entry into monocytes, macrophages, and other cells in addition to causing vascular injury from antigen-antibody complexes. This mechanism of antibody-dependent enhancement may increase the likelihood of DHF in some children and older adults in endemic areas. This may explain why some newborns with passively acquired maternal antibody can develop DHF during initial infection. DHF can also follow infection with a high circulating viral load.
The incubation period from mosquito bite to onset of clinical illness is 4-7 days, with fever an early sign in virtually all infected patients. Initially, the fever is similar to that seen in other viral infections. Fever accompanied by rash, myalgia, thrombocytopenia, and leukopenia should tip off the clinician to the likelihood that the illness is dengue. Dengue infection is typically self-limited. Although primary infection can confer protection from future infection with the same serotype, a second infection can still develop with another dengue serotype.
Infection with dengue virus can be asymptomatic; associated only with mild fever; develop as a flu-like illness with fever, arthralgias, and myalgias; or be severe, displaying the hallmarks of DHF. Classic manifestations of dengue include a biphasic fever, headache, muscle and joint pain, myalgia, lymphadenopathy, and rash. Dengue is sometimes called "break-bone fever" because of the severe arthralgias and myalgias that often develop. Fever may be mild or high, presenting abruptly with photophobia, headache, and retro-orbital pain in addition to the other features of dengue. Less common symptoms include sore throat, altered taste, abdominal pain and tenderness, constipation, inguinal pain, and depression. Nausea and vomiting are frequent, occurring in 60% of patients.
Atypical central nervous system manifestations include encephalopathy, seizures, and behavioral disorders with postinfection sequelae of amnesia and dementia. Furthermore, polyneuropathy, transverse myelitis, and Guillain-Barré syndrome have been reported. Neurologic complications seem more likely following infection with dengue serotypes 2 and 3 and may be a consequence of mononuclear cell release of cytokines that impair the blood-brain barrier or direct infection of the central nervous system by the virus.
Pathogenesis of Dengue Fever and DHF
Dengue fever develops from dengue virus infection following a mosquito bite. Although DHF can develop in patients with a first episode of dengue infection, it appears to be more likely following a second infection with a different serotype of dengue virus. A second viral exposure can result in more severe clinical infection, as preexisting antibodies bind to the virus to enhance viral entry into monocytes, macrophages, and other cells in addition to causing vascular injury from antigen-antibody complexes. This mechanism of antibody-dependent enhancement may increase the likelihood of DHF in some children and older adults in endemic areas. This may explain why some newborns with passively acquired maternal antibody can develop DHF during initial infection. DHF can also follow infection with a high circulating viral load.
Development of Clinical Illness
The incubation period from mosquito bite to onset of clinical illness is 4-7 days, with fever an early sign in virtually all infected patients. Initially, the fever is similar to that seen in other viral infections. Fever accompanied by rash, myalgia, thrombocytopenia, and leukopenia should tip off the clinician to the likelihood that the illness is dengue. Dengue infection is typically self-limited. Although primary infection can confer protection from future infection with the same serotype, a second infection can still develop with another dengue serotype.
Infection with dengue virus can be asymptomatic; associated only with mild fever; develop as a flu-like illness with fever, arthralgias, and myalgias; or be severe, displaying the hallmarks of DHF. Classic manifestations of dengue include a biphasic fever, headache, muscle and joint pain, myalgia, lymphadenopathy, and rash. Dengue is sometimes called "break-bone fever" because of the severe arthralgias and myalgias that often develop. Fever may be mild or high, presenting abruptly with photophobia, headache, and retro-orbital pain in addition to the other features of dengue. Less common symptoms include sore throat, altered taste, abdominal pain and tenderness, constipation, inguinal pain, and depression. Nausea and vomiting are frequent, occurring in 60% of patients.
Atypical central nervous system manifestations include encephalopathy, seizures, and behavioral disorders with postinfection sequelae of amnesia and dementia. Furthermore, polyneuropathy, transverse myelitis, and Guillain-Barré syndrome have been reported. Neurologic complications seem more likely following infection with dengue serotypes 2 and 3 and may be a consequence of mononuclear cell release of cytokines that impair the blood-brain barrier or direct infection of the central nervous system by the virus.
Source...