What does dengue IgG positive mean?

Dengue fever is a common disease to be found in tropical countries such as Malaysia. Apart from Malaysia, other countries in the South-East Asia region including Asia in general and countries in America and Africa are among countries with dengue cases throughout the year. In Malaysia, dengue tends to peak around May to September during the dry southwest and November to March of rainy northeast monsoon seasons. It is even predicted that this year may be the peak of a major outbreak for dengue fever. Do you know that 80{51770bc708b045fac77a8325ad06bcb307cecc80a349eab62160194e87d2e16f} of people infected with dengue infection are actually with no symptoms or only mild infections? Thus, doctors typically use tests to help detect the infections.

There are several tests recommended by doctors to diagnose dengue. Before test is done in those suspected of dengue, common symptoms such as high-grade fever for more than 2 to 7 days and other accompanying symptoms such as headaches with pain behind the eyes (retro orbital headache), joint pain (arthralgia), muscle pain (myalgia) and skin rash can be found in most patients with dengue. Since these signs can be mistaken for other medical conditions, additional tests are usually done by doctors to diagnose dengue. Common tests include dengue virus antigen detection (NS1) and serologic test.

NS1 test is typically used for patients that show dengue symptoms for the first 7 days. This test is not recommended to be used after the 7th day as the result may be inaccurate. A positive NS1 test means a person is infected by dengue virus whereas a negative test result does not necessarily mean a person is not infected by dengue virus.  For negative test results, further tests such as serologic tests are done to detect presence of antibodies against the dengue virus.

While interpretation of NS1 test is easy, it can be different in serologic test. Serologic test detects antibodies responsible for fighting the dengue infection especially IgG and IgM antibodies. Antibodies are substances produced by the body as a result of the immune system attempting to eliminate the dengue infection. Here is where people may get confused as there are 2 kinds of antibodies which are IgM and IgG. IgM antibodies usually appear after the 5th day of fever and can stay in the body for 3 months whereas IgG usually appears later after IgM and remains in the body for life. Positive IgG test usually signifies previous dengue infections whereas positive IgM test suggest the recent dengue infection. Hence, IgM shows recent dengue infection status and IgG shows status of previous dengue infections before the current dengue infection. The importance of knowing IgG and IgM status is to help determine the chances for a person to have a severe form of dengue.

A person with previous dengue infection can have high chances for severe dengue. To better understand this, you have to understand how the immune system works against dengue infection. It is true that in most infectious diseases, a person that has been infected with one will build immunity toward the disease but this is not the entire case with dengue infection. This is because dengue infection has dengue virus in 4 serotypes which are DENV-1, DENV-2, DENV-3 and DENV-4. A person infected by dengue infection will be infected by one of the dengue virus serotypes and recover. After the recovery, a person will only have immunity toward that one specific serotype. Thus, when a person is infected with other serotypes, cross-reacting immunity occurs and this will lead to high risk for severe dengue.

A person diagnosed with dengue fever typically needs treatment to help the patient recover and reduce further complications. There are no specific treatments to eliminate the dengue virus such as antibiotics for bacteria. Treatments available can be considered as supportive ones. Typically, fluid replacement therapy is emphasised through intravenous fluid to maintain good hydration level and to support the patient ‘s circulatory system. Common prescribed medications include paracetamol to ease pain and fever.

Hence, the best way to prevent dengue fever from reaching a severe one is to ensure a person suspected with any of the dengue symptoms gets checked by doctors. Besides knowing the symptoms of dengue fever, it is important to spot warning signs. Warning signs include sudden abdominal pain, presence of blood in stool, vomiting blood, sudden bleeding nose or gums, breathing difficulty, fatigue or restlessness should be signs that the person needs to be brought to the emergency room promptly. People that show warning signs on top of dengue symptoms should be brought to the emergency room immediately as this could progress into life-threatening events. People should also not mistake critical phases as a good sign. Critical phase occurs when dengue symptoms seem to disappear on the 3rd to 7th days of the disease and this is actually the most dangerous part of dengue infection as it can suddenly lead to severe dengue or even death when left unattended by healthcare professionals. Critical phase lasts for 24 to 48 hours.

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