Dengue was known as ''water poison''in past for its association with insects found near any water bodies.
Transmission of dengue :
Dengue is transmitted by bite of aedes aegypti or aedes albopyctus mosquitoes. This bite transmits dengue viruses from mosquitoes to human bloodstream causing dengue fever. Dengue virus belongs to Flaviviridae family. There are four types of related but antigenically different dengue viruses namely DENV-1,DENV-2,DENV-3,DENV-4. Infection with one type of virus gives lifelong immunity for that perticular virus but dengue fever can recur due ti cross infection with other virus type. Recurrent infection with dengue virus can be more severe than first episode due to cytokine stormand presence of non-neutralising antibodies.
Another way of dengue virus transmission is through blood transfusion.If a person is transfused with blood from a person who is having circulating virus in bloodstream,he can get dengue infection.
Characteristics of aedes aegypti mosquitoes :
- Aedes mosquitoes lays their eggs in fresh water and in artificial containers like flower vases,old automobile tyres,buckets that collect rain water,coolers,large drums,septic tanks
- Aedes mosquitoes remains indoors and bite human beings during daytime. Two major peak periods of bitting are early in the morning 2-3 hours after day break and in afternoon many hours before dark.
- Aedes mosquitoes are voraceous feeders and bites same person multiple times. Surprisingly they can infect many people in same house within 24-36 hours time period.
- Their flight range is 100 meters and they don't fly high hence bite more on legs.
What is the intrinsic and extrinsic incubation period of dengue virus?
Intrinsic period is the time taken by virus to complete its development in definitive host that is human being.Intrinsic incubation period of dengue virus is 2-10 days.That means after bitten by aedes aegypti mosquito, it takes 2-10 days to develope fever and other symptoms of dengue illness.During this time virus remains in blood circulation and if another aedea aegypti mosquito bites that person,that mosquito will carry that virus and can infect anothe person.
Extrinsic incubation period is the time taken by virus to develop in intermediate host.Extrinsic incubation period of dengue virus is 8-12 days inside aedes aegypti mosquito.
When does incidence of dengue illness is at its peak?
In india dengue illness is at its peak from june to october. Various environmental factors are responsible for it.They are as follows:
- After rainfall water stagnates in artificial containers and aedes mosquitoes breed in that water.
- In higher temperature,Mosquitoes takes less time to mature and lays more eggs during this period.
- In warmer climates,mosquitoes bite frequently as digestion of blood is faster in this time.WHO estimated that 1-2 degree rise in temperature increases vulnerable population by 700 million per annum.
Pathogenesis of dengue :
In dengue,vascular permeability increases due to loss of negative charge of glycocalyx of capillary endothelium. This allows water from blood to accumulate in abdominal,thoracic cavity and in organ tissues. This leads to development of pulmonary edema,pleural effusion,ascitis,brain edema leading to coma. Dendue patients also suffer from hepatitis and may have deranged liver function test.
Cytokine storm is responsible for dengue hemorrhagic fever vasculopathy.Massive T-Lymphocyte activation underlies cytokine storm.Antibodies detected against DENV NS1 cross reacts with platelets and endothelium leading to low platelet count(thrombocytopenia) and capillary leak.
What are the signs and symptoms of dengue?
There is a wide spectrum of clinical features in dengue ranging from asymtomatic to dengue shock syndrome and coma leading to death.
According to symptoms dengue if differentiated into following groups :
1.Dengue fever :
Symptoms of dengue fever are fever lasting for 2-7 days with bodyache, myalgia,retro-orbital pain, headache rash and arthralgia,suffused and swollen face,red eyes. The myalgia and bodypain is due to inflammation in musclea and has nothing to do with ligamenr tears.
Sometimes people confuse dengue rash with allergic rash.We can differentiate it very well. Dengue rash is always associated with fever and can have itching associated with it.Allergic rash is hyperacute in occurence after allergen exposure without fever,is associated with itching and respiratory symptoms like breathing difficulty many a times and moreover there is past history of similar illness in past.
2.Dengue hemorrhagic fever :
In this,patient will have fever associated with bleeding tendensies like positive tourniquet test,petechiae,mucosal bleed ,nasal bleed ,black colored stools,purpura,bleeding from injection site.
Platelet count in this patients is usually less than 1 lakhs.Along with this there will be rise in hematocrit(packed cell volume PCV) by 20%.Hence checking hemoglobin,PCV and platelet counts is very important in dengue patients.
3. Dengue shock syndrome :
In this patient will have low BP and hypotension with shock.Patient may go into coma like state.
What are the warning signs in dengue patient?
Some of the warning signs in dengue patients are:
- Abdominal pain and tenderness
- Clinical fluid accumulation
- Mucosal bleed
- Lethargy and restlessness
- Liver enlargement > 2 cm
- Laboratory increase in PCV (hematocrit) associated with decrease in platelet count
Clinical course of dengue fever :
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| Fig : clinical course of dengue |
There are three phases of dengue illness. Febrile,critical and recovery phase.
1. Febrile phase :
It is a phase of viremia.In febrile phase,it may not be always possible to differentiate dengue from non-dengue illnesses.Patient will have high grade fever with chills and rigors during this phase. Actually during this illness thermoregulatory centre in hypothalamus is set on higher temperature due to release of chemicals called pyrogens. This signals body to maintain temperature at higher level hence patient will shiver in an attempt to raise body temperature and will have rigors too.
Patient will have decreased WBC count(Leukopenia) ,atypical lymphocytosis and thrombocytopenia during this phase. These changes are due to attack of virus over body's immune system.
This phase will last for 2-7 days after which patients start recovering or could pass into critical phase if deteriorates.
2. Critical phase :
This is the phase in which capillary leak becomes prominant and plasma will leak into body cavities and organ tissues.Patient will have low Blood pressure ,shock and hemorrhage leading to anemia.
Laboratory parameters will reveal rising hematocrit with thrombocytopenia and low hemoglobin. Patients may need to transfuse platelets and packed red cells(hemotransfusion) to correct thrombocytopenia and anemia respectively.
3. Recovery phase :
In this phase body starts reabsorbing fluids from body cavities back into capillaries and platelets starts rising and leukopenia starts correcting.Sometimes patients can have fluid overload due to reabsorption of fluid and hence to be watched for it.
Generally once platelet count and WBC count starts rising it will not fall back unless patient is complicated by secondary infection.
Which are the organs affected in dengue patients and symptoms associated with it?
1.Hepatitis :
Hepatitis can occur in 30-40% of dengue patients.This will present in form of hepatomegaly and raised liver enzymes.SGOT,SGPT,LDH (Lactate Dehydrogenase) will be raised by day 3 of illness and will peak by 7-8th day of illness and will resolve by 3-8 weeks. Sometimes patient can have jaundice and hepatic failure leading to bleeding manifestations( coagulopathy) hence prothrombin time (PT) and Activated partial prothrombin time(APTT) should be done in these patients.Sometimes patients can have pancreatitis which is transient and reversible.
2.Neurological complications :
Dengue patients can suffer with encephalitis,convulsions,unconsciousness, raised intracranial tension and coma.
3. Cardiac and respiratory complications :
Heart is affected in dengue illness leading to its decresed function, hypokinesia, decresed ejection fraction, ECG changes due to myocarditis, Rhythm disturbances. Majority of the changes are transient and reversible.
Lung is also affected in dengue either due to pulmonary edema or pleural effusion.Patient can have cough and breathing difficulties.
How dengue illness is diagnosed?
Doctors will advice some blood tests for diagnosing dengue fever.
NS1 antigen test ,Dengue IgG and dengue IgM test:
- Serology ( Dengue IgG and IgM) may not be positive in febrile phase, but NS1 antigen will come positive in febrile phase from day 2 of illness. NS1 is highly specific and sensitive for dengue diagnosis.
- Dengue IgM positivity indicates acute and recent infection with dengue virus. It will start appearing in blood after day 5 of illness and will disappear by 2-3 months.
- Dengue IgG positivity indicateds remote infection with dengue virus. Dengue IgG appears afetr 1-2 Weeks of infection and persist for life hence it is not specific for recent infection.
- Hence Dengue IgM positivity with Dengue IgG positivity indicated recurrence of dengue infection with another dengue virus type.
Patient is declared as cured based on clinical parameters and on the basis of correction of hematological tests.
What are the hematological test findings in dengue?
Dengue patients will have thrombocytopenia, rise in hematocrit and white cell count could be normal or decresed.
What is the biochemical profile in dengue patient?
- Prothrombin time ( PT) and APTT could be normal or prolonged in case of hepatitis.
- Electrolyte abnormalities : Hyponatremia
- Acidosis in case of shock
- Kidney function tests : In critical phase patients can have elevated urea and creatinine level which can be reversed with intravascular volume restoration.
- Liver function tests : In case of hepatitis,patients can have elevated levels of transaminases SGOT,SGPT along with elevated LDH.Sometimes patients can have eleveted total bilirubin .
What is the treatment of dengue?
Dengue is a viral illness with no specific treatment. Symptomatic management and prevention of complications is the key to manage patient with dengue illness. Different managements available for dengue are:
1. Antipyretics and Painkillers :
These are mainly used to relieve fever and bodyaches,headaches,retro-orbital pain and decrease patient's discomfort. Paracetamol , Mefenamic acid are the available antipyretics and painkillers. Avoid giving Ibugesic in dengue patients as it can cause thrombocytopenia. If patient has allegy to paracetamol he can use mefenamic acid.
Available brands in market are : Calpol , Dynapar ( Diclofenac Sodium+Pracetamol)
2. Antiemetics :
Many dengue patients have nausea and vomitting hence doctors will prescribe antiemetics like Ondensetron or Domperidone for that.
3. Medications for acidity :
Sometimes doctor will prescribe pantoprazole or ranitidine for heartburn in dengue patients. Example-Zineta 150. These medications can be taken by patients to treat after dengue illness heartburn and acidity.
4. Intravascular fluid :
Doctors usually give dextrose normal saline or ringer lactate to dengue patients as oral intake of patients is low moreover patients may have low blood pressure due to capillary leake and dengue hemorrhagic shock.This is mainly given to restore intravascular volume and prevention of shock in dengue patient.
5. Antibiotics :
Antibiotics are generally not indicated in dengue patients. But sometimes doctor may give ceftriaxone or cefotaxime to patients to prevent secondary infection or to treat peritonitis.
6. Platelet transfusion and hemotransfusion :
Thrombocytopenia with bleeding manifestations is the indication for platelet transfusion in dengue patient. Red blood cell transfusion is given to patients with low hemoglobin and shock in case of dengue hemorrhagic shock.
7. Papaya extract :
Some medications containing papaya extract are available in market like Platenza,Platimax , Treplate. Till the date,research has not established any beneficial role of papaya extract,goat milk,kiwi ,bottle guard ingestion on improvement of thrombocytopenia.
Measures to prevent dengue infection :
1. Prevent breeding of aedes mosquitoes :
Don't allow water to stagnate in artificial containers.Follow one day per week as dry day and drain all the containers that day. Dispose plastic and disposables well to prevent stagnation of water. Fill all the defects on road with cement.
2. Prevent bite from aedes mosquitoes :
Keep doors closed during daytime.use mosquitoes repellents like all our. Apply Odomos while going out. Use mosquito nets while sleeping.
3. Breed Gappi fish in stagnant water :
Gappi fish feeds on aedes mosquitoes hence controlling their multiplication. Also you can put some kerosene over stagnant water surface to prevent mosquitoe breeding.
4. Keep dengue patients in mosquito net :
Avoid any mosquito bite to dengue patient so that other family members don't get bite from that same mosquito.
5. Inform municipalty about dengue patient in your area :
Usually all hospitals notify authority and municipalty about dengue patients and their address so that municipalty will take actions to control mosquitoes in that area.
What will happen if a menstruating girl/women gets dengue infection?
As far as platelet count is above 1 Lakhs, patient will not have any major bleeding manifestation. In case platelet count drops below 1 Lakhs, girl can have heavy blood loss during menstruation and can become anemic.Medications enhancing coagulation can be given in such cases.
Dengue infection during pregnancy:
Dengue infection can complicate pregnancy and can be a danger for maternal health. Mother can go into premature labour,shock or can have heavy blood loss during delivery. Caeserean delivery sometimes can be difficult in such mothers dur to fever,hypotension,thrombocytopnia and anemia. Dengue infection can spread to baby transplacently.
Dengue illness and corona :
Till now research has not established effect of past corona infection or dengue illness on each other in terms of severity and protective response.
How to take care of patient after recovering from dengue?
After recovering from dengue illness,patient can fill lethargic,weak for 1-2 months.This is mainly due to decresed appetite and oral intake during period of illness and effect of virus on immune system.After recovery,appetite starts improving. Give patients a healthy and balanced diet containing adequate protein. Also you can give potassium rich foods and coconut water to restore electrolyte disturbances. Allow patients to take adequate bed rest and sleep.Some patients can have itching even after recovery which can be treated with application of emolient. Some patients complain of acidity and nausea which can be managed by giving antacids and antiemetic drugs.Some doctors prescribe multivitamin tablets to restore any vitamine deficiency occured during illness. Liv 52 has not been proven of any additional benefit in dengue.
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