all about Dengue What is Dengue? Dengue is caused by four closely related viruses (DEN-1, DEN-2, DEN-3 or DEN-4). It is transmitted to humans by the bite of the infected mosquito. Dengue fever is a severe, flu-like illness that affects infants, young children and young adults but rarely causes death. The two most severe forms of dengue are Dengue Haemorraghic Fever (DHF) and Dengue Shock Syndrome (DSS). How is it transmitted? Dengue viruses are transmitted to humans through bites of the infected female Aedes mosquito. Mosquitoes generally acquire the virus while feeding on the blood of a person who has dengue. Once infected, a mosquito is capable of transmitting the virus to susceptible individuals for the rest of its life. The dengue virus circulates in the blood of the infected humans for 3-14 days (average 4 to 6 days). The person may experience sudden onset of fever accompanied by a variety of non-specific signs and symptoms. Dengue cannot be spread directly from person to person. What are the symptoms? The signs and symptoms of dengue fever vary according to the age of the patient. The principal symptoms of dengue are high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain and rash. Infants and young children may have a fever and a rash. They have milder illness compared to other older children and adults. Headache Fever Eye pain Muscle pains Joint pains Rash Example of a typical dengue rash. Dengue Haemorrhagic Fever and Dengue Shock Syndrome Dengue Haemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS) are characterised by a sudden onset of fever, as high as 40-41ºC, lasting about 2-7days with similar signs and symptoms of dengue fever. This is followed by “leaky” capillaries allowing fluid component to escape from the blood vessels causing shock and hemorrhagic manifestations such as bleeding nose or gums, and possibly internal bleeding. Platelet counts will fall to less than 100,000/mm3. The course of DHF is 7-10 days. During the acute phase of dengue, it is difficult to distinguish DHF/DSS from Dengue fever and other viral illnesses. The critical stage of DHF/DSS occurs most frequently from 24 hours after the temperature falls to or below normal. If Dengue Haemorrhagic Fever is not treated, it can lead to Dengue Shock Syndrome. In patients with severe DHF or DSS, fever and non-specific signs and symptoms of a few days are followed by the sudden deterioration of the patient’s condition. The patient may appear lethargic at first and become restless. The signs of circulatory failure include: • low blood pressure • rapid and weak pulse • acute abdominal pain • cold clammy skin and restlessness Subconjunctival bleeding Nosebleeds Skin bruising Bleeding in the gut Pin point skin bleeding Signs of haemorrhage are common and include bleeding under the skin (petechiae and purpura), gum bleeding, bleeding from the nose and gastrointestinal tract and heavy menstrual flow. They frequently experience acute abdominal pain shortly before the onset of shock. Incubation period (Time between mosquito’s bite to onset of symptoms) The incubation period for Dengue Fever and Dengue Haemorrhagic Fever lasts from 3 to 14 days. The average incubation period is 4-6 days. How can dengue be confirmed? Dengue infection is diagnosed in the laboratory by detecting specific antibodies in the patient’s serum (serological test) from fifth day of fever. If necessary, the test should be repeated 2-3 weeks later. A number of rapid test kits based on single serum samples are commercially available but may be less sensitive than conventional serological test. In the first five days of fever, dengue infection can be diagnosed by molecular detection (polymerase chain reaction) and dengue antigen testing (NS 1 antigen). Blood for diagnostic testing should be taken from patient as soon as possible after the onset of symptoms. What kind of treatment is available for Dengue fever? There is no antiviral drug to treat dengue. Treatment is largely to manage the symptom and to prevent the complications arising from severe DHF and DSS. Early management depends on close daily monitoring of the platelet count, so that patient can receive fluid replacement therapy and platelet transfusion if necessary. • If you think you are having dengue, consult a doctor or go to the Accident and Emergency Department of the nearest hospital. Early detection and treatment of the symptom can be life saving. • If the doctor suspects Dengue Haemorrhagic Fever, you will be admitted in the hospital. Your blood pressure and blood count will be closely monitored. • Persons who think they have dengue should use pain relievers eg. Acetaminophen or paracetamol. They should rest, drink plenty of fluids and consult a doctor. What is the infectious period after the onset of symptoms? An infected individual will not infect others by direct contact. However, if a person is bitten by a mosquito during the initial febrile period of the dengue infection, the mosquito may become infected and transmit the dengue virus to the next person through its bite. Can dengue infection recur in a previously infected person? There are 4 types of Dengue virus. Infection with one type does not provide long term protection against other strains. There is also evidence that the risk of developing DHF/DSS is increased in the persons previously infected by another type. Frequently asked questions 1. How can I avoid getting infected with Dengue? The best way to avoid Dengue is to avoid bites by the Aedes mosquito. The mosquito that transmit Dengue lives and breed near residential areas or within homes. Breeding occurs where water is stagnant eg. in small containers, flower pots etc. Dengue is also imported by persons carrying the virus with them. Foreigners and Singaporeans returning from Dengue-endemic countries may also be infected. It is advisable to avoid getting mosquito bites in high-risk areas. Precautions include staying in screened or air-conditioned rooms, using aerosol insecticides to kill the adult mosquitoes indoors and using an insect repellent containing 20% - 30% DEET (diethyltoluamide). Always stay informed of any ongoing epidemics in the country that you are about to visit. 2. Can I get vaccinated against Dengue? There is no effective and safe vaccine against dengue, so it is vital to take precautions to avoid getting infected through infective mosquito bites. Research is currently ongoing in the search for an effective dengue vaccine. 3. How can we prevent and control dengue in Singapore? The public is constantly reminded to keep their homes free of dengue by adopting a routine system of checks for Aedes breeding habitats within and around their homes. They may also apply insecticides and granules in watercontaining receptacles. Residents of landed properties are advised to repair and remove defective roof gutters and to apply insecticide paint on roof gutters and flower pot plates. Items that collect rainwater or used to store water (eg plastic containers, buckets or used automobile tires) should be covered or properly discarded. Ask-a-CGH Nurse Internet Service Changi General Hospital has an Ask-a-CGH Nurse Service on our website. This service is an additional avenue for you to ask questions about any signs, symptoms, or health related concerns you may have. The service is provided by our team of experienced nurses, in consultation with our medical specialists and paramedical staff. This service is not intended to substitute medical advise or consultation. To use this service, go to our website at http://www.cgh.com.sg and click on “Ask-a-CGH Nurse” to submit your question. You will hear from us within three working days. Interactive Patient Guide www.cgh.com.sg/ipg CGH is pleased to introduce the interactive Patient Guide (IPG) – Singapore’s first online interactive health education system. Developed by our team of clinical specialists, IPG provides an exciting multimedia alternative to health-related information. IPG features a list of common medical conditions, treatments, procedures, postprocedures and aftercare through videos and printable text. The video clips allow you to see exactly how a procedure is carried out or details on a health condition. For greater convenience, print-friendly versions are also available so that you can print and read at your own pace. With IPG on the Internet, you can explore it anytime you want, in the comfort of your own home and even share it with your family and friends. Log on today! Organisation Accredited by Joint Commission International 03/2009