Dengue and severe dengue
crucial data
Dengue is a viral infection transmitted to humans direct the bite of infected mosquitoes. The primary vectors that transmit the complaint are Aedes aegypti mosquitoes and, to a lower extent, Ae. albopictus.
The contagion behind for causing dengue, is called dengue contagion( DENV). There are four DENV serotypes and it's possible to be infected four times.
acute dengue is a leading cause of serious illness and death in some Asian and Latin American countries. It requires operation by medical professionals.
There's no specific treatment for dengue/ severe dengue. Beforehand discovery of complaint progression associated with severe dengue, and access to proper medical care lowers casualty rates of severe dengue to below 1.
Dengue is set up in tropical andsub-tropical climates worldwide, substantially in civic andsemi-urban areas.
Overview
Dengue is a mosquito- borne viral complaint that has fleetly spread to all regions of WHO in recent times. Dengue contagion is transmitted by womanish mosquitoes substantially of the species Aedes aegypti and, to a lower extent, Ae. albopictus. These mosquitoes are also vectors of chikungunya, unheroic fever and Zika contagions. Dengue is wide throughout the tropics, with original variations in threat told by climate parameters as well as social and environmental factors.
Global burden
The prevalence of dengue has grown dramatically around the world in recent decades. A vast maturity of cases are asymptomatic or mild and tone- managed, and hence the factual figures of dengue cases are under- reported. numerous cases are also misdiagnosed as other febrile ails( 1).
One modelling estimate indicates 390 million dengue contagion infections per time( 95 believable interval 284 – 528 million), of which 96 million( 67 – 136 million) manifest clinically( with any inflexibility of complaint)( 2). Another study on the frequence of dengue estimates that3.9 billion people are at threat of infection with dengue contagions. Despite a threat of infection being in 129 countries( 3), 70 of the factual burden is in Asia( 2).
Distribution and outbreaks
Before 1970, only 9 countries had endured severe dengue pandemics. The complaint is now aboriginal in further than 100 countries in the WHO regions of Africa, the Americas, the Eastern Mediterranean, South- East Asia and the Western Pacific. The Americas, South- East Asia and Western Pacific regions are the most seriously affected, with Asia representing
70 of the global burden of complaint.
Transmission
Transmission through mosquito bite
The contagion is transmitted to humans through the mouthfuls of infected womanish mosquitoes, primarily the Aedes aegypti mosquito. Other species within the Aedes rubric can also act as vectors, but their donation is secondary to Aedes aegypti.
After feeding on an DENV- infected person, the contagion replicates in the mosquito midgut, before it disseminates to secondary apkins, including the salivary glands. The time it takes from ingesting the contagion to factual transmission to a new host is nominated the foreign incubation period( EIP). The EIP takes about 8- 12 days when the ambient temperature is between 25- 28 °C( 4- 6). Variations in the foreign incubation period aren't only told by ambient temperature; a number of factors similar as the magnitude of diurnal temperature oscillations( 7, 8), contagion genotype( 9), and individual viral attention( 10) can also alter the time it takes for a mosquito to transmit contagion. Once contagious, the mosquito is able of transfer contagion for the rest of its life.
mortal- to- mosquito transmission
Mosquitoes can advance infected from people who are viremic with DENV. This can be someone who has a quality dengue infection, someone who's yet to have a characteristic infection( they arepre-symptomatic), but too people who show no signs of illness as well( they are asymptomatic)( 11).
Mortal- to- mosquito transmission can do up to 2 days before someone shows symptoms of the illness( 5, 11), up to 2 days after the fever has set on( 12).
motherly transmission
The primary mode of transmission of DENV between humans require mosquito vectors. There's substantiation still, of the possibility of motherly transmission( from a pregnant mama to her baby). While perpendicular transmission rates appear low, with the threat of perpendicular transmission putatively linked to the timing of the dengue infection during the gestation( 14- 17). When a mama does have a DENV infection when she's pregnant, babies may suffer frompre-term birth, low birthweight, and fetal torture( 18).
Other transmission modes
Rare cases of transmission via blood products, organ donation and transfusions have been recorded. also, transovarial transmission of the contagion inside mosquitoes have also been recorded.
Vector Ecology
The Aedes aegypti mosquito is considered the original vector of DENV. It could breed in natural holders similar as tree holes and bromeliads, but currently it has well acclimated to civic territories and types substantially in man- made holders including pails, slush pots, discarded holders and used tyres, storm water rainspoutsetc., therefore making dengue an insidious complaint in densely peopled civic centers. Ae. aegypti is a day- time confluent; its peak smelling ages are early in the morning and in the evening before evening( 19) womanish Ae. aegypti constantly feed multiple times between each egg- laying period leading to clusters of infected individualities( 20). Once a lady has laid her eggs, these eggs can remain feasible for several months in dry condition, and will door when they're in contact with water.
Disease characteristics( signs and symptoms)
While maturity of dengue cases are asymptomatic or show mild symptoms, it can manifest as a severe, flu- suchlike illness that affects babies, youthful children and grown-ups, but infrequently causes death. Symptoms generally last for 2 – 7 days, after an incubation period of 4 – 10 days after the bite from an infected mosquito( 25). The World Health Organization classifies dengue into 2 major orders dengue( with/ without advising signs) and severe dengue. Thesub-classification of dengue with or without advising signs is designed to help health interpreters triage cases for sanitarium admission, icing close observation, and to minimize the threat of developing the more severe dengue( 25).
Dengue
Dengue should be suspected when a high fever( 40 °C/ 104 °F) is accompanied by 2 of the following symptoms during the febrile phase( 2- 7 days)
severe headache
pain behind the eyes
muscle and joint pains
nausea
vomiting
blown glands
rash.
Severe dengue
A patient enters what's called the critical phase typically about 3- 7 days after illness onset. During the 24- 48 hours of critical phase, a small portion of cases may manifest unforeseen deterioration of symptoms. It's at this time, when the fever is dropping( below 38 °C/ 100 °F) in the case, that advising signs associated with severe dengue can manifest. Severe dengue is a potentially fatal complication, due to tube oohing, fluid accumulation, respiratory torture, severe bleeding, or organ impairment.
Warning signs that croakers
should look for include
severe abdominal pain
patient vomiting
Rapid-fire breathing
bleeding epoxies or nose
fatigue
restlessness
liver blowup
blood in heave or coprolite.
still, close observation for the coming 24 – 48 hours is essential so that proper medical care can be handed, to avoid complications and threat of death, If cases manifest these symptoms during the critical phase. Close monitoring should also resume during the convalescent phase.
Diagnostics
Several styles can be used for opinion of DENV infection. Depending on the time of patient donation, the operation of different individual styles may be more or less applicable. Case samples collected during the first week of illness should be tested by both styles mentioned below
Contagion insulation styles
The contagion may be insulated from the blood during the first many days of infection. colorful rear transcriptase – polymerase chain response( RT – PCR) styles are available and are considered the gold standard. still, they bear specialised outfit and training for staff to perform these tests.
The contagion may also be detected by testing for a contagion- produced protein, called NS1. There are commercially- produced rapid-fire individual tests available for this, and it takes only
20 mins to determine the result, and the test doesn't bear technical laboratory ways or outfit.
Serological styles
Serological styles, similar as enzyme- linked immunosorbent assays( ELISA), may confirm the presence of a recent or once infection, with the discovery ofanti-dengue antibodies. IgM antibodies are sensible
1 week after infection and remain sensible for about 3 months The presence of IgM is reflective of a recent DENV infection. IgG antibody situations take longer to develop and remains in the body for times. The presence of IgG is reflective of a once infection.
Treatment
There's no specific treatment for dengue fever. Cases should rest, stay doused and seek medical advice. Depending on the clinical instantiations and other circumstances, cases may be move home, be appertained for in- sanitarium operation, or bear exigency treatment and critical referral( 25).
probative care similar as fever reducers and pain killers can be taken to control the symptoms of muscle pangs and pains, and fever.
Vaccination against dengue
The first dengue vaccine, Dengvaxia ®( CYD- TDV) developed by Sanofi Pasteur was certified in December 2015 and has now been approved by nonsupervisory authorities in
20 countries. In November 2017, the results of an fresh analysis to retrospectively determine serostatus at the time of vaccination were released. The analysis showed that the subset of trial actors who were inferred to be seronegative at time of first vaccination had a advanced threat of more severe dengue and hospitalizations from dengue compared to unvaccinated actors. As similar, use of the CYD- TDV vaccine is targeted for persons living in aboriginal areas, 9- 45 times of age, who have had at least 1 occasion of dengue contagion infection in the history. Several fresh dengue vaccine campaigners are below evaluation.
WHO position on the CYD- TDV vaccine( 26)
As described in the WHO position paper on the Dengvaxia vaccine( September 2018)( 26) the live downgraded dengue vaccine CYD- TDV has been shown in clinical trials to be efficient and safe in persons who have had a former dengue contagion infection( seropositive individualities). For countries considering vaccination as part of their dengue control programme,pre-vaccination webbing is the recommended strategy. With this strategy, only persons with substantiation of a once dengue infection would be vaccinated( grounded on an antibody test, or on a proved laboratory verified dengue infection in the history). opinions about enforcing apre-vaccination webbing strategy will bear careful assessment at the country position, including consideration of the perceptivity and particularity of available tests and of original precedences, dengue epidemiology, country-specific dengue hospitalization rates, and affordability of both CYD- TDV and webbing tests.
threat factors
Former infection with DENV increases the threat of the individual developing severe dengue.
Urbanization( especially unplanned), is associated with dengue transmission through multiple social and environmental factors population viscosity, mortal mobility, access to dependable water source, water storehouse practice etc.
Prevention and control
still, avoid getting farther mosquito mouthfuls during the first week of illness, If you know you have dengue. Contagion may be circulating in the blood during this time, and thus you may transmit the contagion to new uninfected mosquitoes, who may in turn infect other people.
The propinquity of mosquito vector parentage spots to mortal habitation is a significant threat factor for dengue. At present, the main system to control or help the transmission of dengue contagion is to combat the mosquito vectors. This is achieved through
WHO response
WHO responds to dengue in the following ways
supports countries in the evidence of outbreaks through its uniting network of laboratories;
provides specialized support and guidance to countries for the effective operation of dengue outbreaks;
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