Beware Of That Mosquito


With the advent of monsoon, there is a general rise in vector-borne diseases. Vectors are living organisms that act as carriers of infectious diseases between humans or from animals to humans. Vector-borne diseases are illnesses caused by pathogens and parasites. Dengue fever is endemic in tropical and subtropical areas such as South Asia, South and Central America and the Caribbean.  An outbreak of dengue fever that had strike New Delhi a couple of years ago, was counted as the worst in the last five years. Numbers revealed that over 10,000 people tested positive for dengue fever, and there had been at least 32 deaths attributed to that outbreak, however, the actual numbers of people in India with dengue remained vastly under-reported. The hospitals run by the state were so outpouring with patients that they had to share beds.

According to research, four closely related viruses cause dengue fever, Dengue 1 2 3 and 4. The viruses are transmitted by Aedes aegypti mosquitoes to humans in a viral life cycle that require both humans and these mosquitoes. The virus cannot spread directly from human-to-human. Once a mosquito is infected, it remains infected for its lifespan. A human can infect mosquitoes when the human has a high number of viruses in the blood which is usually the period right before symptoms develop). Aedes aegypti species of mosquito is a daytime biting mosquito and it bites mostly in the early mornings or late in the afternoons.

Dengue can range from a mild infection to a more severe form known as dengue hemorrhagic fever which can lead to a fatal condition known as the dengue shock syndrome.

The primary symptoms of dengue appear 3 to 15 days after the mosquito bite and usually include the following:

  • High fever
  • Severe headache
  • Severe pain behind the eyes that is apparent when trying to move the eyes
  • Joint and muscle pain
  • Swollen lymph nodes
  • Exhaustion and rash (actually, the presence of fever, rash, and headache: the ‘dengue triad’ is characteristic of dengue fever)
  • Lower back ache
  • Mild bleeding

What are the tests for Dengue?

By various tests, we can know about the presence of viral antigens in blood, for e.g. NS1 test. Apart from this when the viral antigens are administered to our bodies, our bodies form immunoglobulins as a defense mechanism against the virus. By serology test, we can measure the level of immunoglobulins to confirm the presence of Dengue fever. Examples of these tests are IgG and IgM for dengue. There is a specific test known as PCR polymerase chain reaction which can detect even minute quantities of viral antigen. But this test is done very rarely and is quite expensive. Apart from these, the platelet count is also monitored in dengue patients. The platelet count starts decreasing after 5th or 6th day of fever. But routinely this test is not for diagnosing the dengue rather it is used to monitor if the patient needs to be transfused platelets or not.

How to choose which tests to go for?

If the fever is for the past two days only then one should go for the NS1 test. If NS1 is positive then the patient is most likely suffering from dengue.

If the fever has been there for the past 5 to 6 days then it is advisable to go for serology IgG and IgM tests. The interpretation of these tests is a little complicated. If IgG and IgM both are positive then it implies a current infection. If IgM is negative then it indicates an infection in the past.

If PCR is positive then dengue is positive.

Since platelet count starts falling only after 5 to 6 days, it should be done then.

Dengue is in general self-limited and usually adequate hydration and management of pain will help the person through the infection. This is a redeeming factor. However, for dengue fever, a caution is necessarily given by most doctors regarding treatment at home. Nonsteroidal anti-inflammatory agents (for example, aspirin, ibuprofen and other NSAIDs) should be avoided because dengue viruses have the tendency in them to cause hemorrhages. Ibuprofen is anyway a banned in India. The NSAIDs may add to the hemorrhage symptoms and cause bleeding.
In cases where more severe variations of dengue fever (hemorrhagic and shock syndrome) have occurred, it mandatorily requires hospitalization. IV fluid hydration, blood pressure support, blood transfusions, platelet transfusions,  and other intensive-care measures may need to be administered to these patients.

The most serious complications, although infrequent, are as follows:

  • Dehydration
  • Bleeding (hemorrhage)
  • Low platelets
  • Low blood pressure(hypotension)
  • Slow heart rate (bradycardia)
  • Liver damage
  • Neurological damage (seizures, encephalitis)
  • Death

How to stay protected from mosquito bites?

There is no vaccine to prevent dengue fever. The best method of protection is to avoid mosquito bites and to reduce the mosquito population. When in a high-risk area, you should:

  • Avoid ghettoized residential areas where sanitation and hygiene have been compromised. If you stay in such an area, take steps to maintain cleanliness.
  • Ensure that there is no stagnation of water in containers or water bodies in or around your house. Keep all water containers closed with a lid and cleaned on a regular basis.
  • Use mosquito repellent indoors and outdoors like patches, sprays, and lotions. Use these repellents in accordance with the instructions on the labels and after advice from your doctor.
  • Wear long-sleeved shirts and pants tucked into socks and closed shoes when venturing outdoors.
  • Use air conditioning instead of opening windows. Ensure that window and door screens are secure, and any holes are repaired. Mesh the doors and windows of your home to keep it mosquito free.
  • Use mosquito nets if sleeping areas are not screened.

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