How to prevent dengue fever?

Dengue fever is a viral infection that spreads from mosquito to peaple.

its more common in tropical and subtropical climates.

Symptoms of dengue fever are :-

• High grade fever.
• Sever headache.
• Pain behind the eyes.
• Muscle and joint pain.
• Nausea and vomiting.
• Swollen glands.
• Rash.

People with these severe symptoms should get care right away. 

After recovery, people who have had dengue may feel tired for several weeks.

Diagnose and treatment.

There is no specific treatment for dengue fever ,focus on treating pain syptoms.

Most cases of dengue fever can be treated at home with a pain medicine.

Treatment acetaminophen is recommended ,Non-steroidal anti-inflammatory drugs like ibuprofen and aspirin are avoided as they can increase the risk of bleeding.

For people with severe dengue, hospitalization is often needed.

Transmission.

he dengue virus is transmitted to humans through the bites of infected female mosquitoes, primarily the Aedes aegypti mosquito. Other species within the Aedes genus can also act as vectors, but their contribution is normally secondary to Aedes aegypti. However, in 2023, a surge in local transmission of dengue by Aedes albopictus (tiger mosquito) has been seen in Europe.

After feeding on a infected person, the virus replicates in the mosquito midgut before disseminating to secondary tissues, including the salivary glands. The time it takes from ingesting the virus to actual transmission to a new host is termed the extrinsic incubation period (EIP). The EIP takes about 8–12 days when the ambient temperature is between 25–28°C. Variations in the extrinsic incubation period are not only influenced by ambient temperature; several factors such as the magnitude of daily temperature fluctuations, virus genotype, and initial viral concentration can also alter the time it takes for a mosquito to transmit the virus.

Human-to-mosquito transmission

Mosquitoes can become infected by people who are viremic with the dengue virus. This can be someone who has a symptomatic dengue infection, someone who is yet to have a symptomatic infection (they are pre-symptomatic), and also someone who shows no signs of illness (they are asymptomatic).

Human-to-mosquito transmission can occur up to 2 days before someone shows symptoms of the illness, and up to 2 days after the fever has resolved.

The risk of mosquito infection is positively associated with high viremia and high fever in the patient; conversely, high levels of DENV-specific antibodies are associated with a decreased risk of mosquito infection. Most people are viremic for about 4–5 days, but viremia can last as long as 12 days.

Maternal transmission

The primary mode of transmission of the dengue virus between humans involves mosquito vectors. There is evidence however, of the possibility of maternal transmission (from a pregnant mother to her baby). At the same time, vertical transmission rates appear low, with the risk of vertical transmission seemingly linked to the timing of the dengue infection during the pregnancy. When a mother does have a dengue infection when she is pregnant, babies may suffer from pre-term birth, low birthweight, and fetal distress.

Other transmission modes

Rare cases of transmission via blood products, organ donation and transfusions have been recorded. Similarly, transovarial transmission of the virus within mosquitoes have also been recorded. 

Risk factors

Previous infection with DENV increases the risk of the individual developing severe dengue.

Urbanization (especially unplanned), is associated with dengue transmission through multiple social and environmental factors: population density, human mobility, access to reliable water source, water storage practice etc.

Community risks to dengue also depend on a population’s knowledge, attitude and practice towards dengue, as the exposure is closely related to behaviours such as water storage, plant keeping, and self-protection against mosquito bites.  Routine vector surveillance and control activities engaging community greatly enhances a community’s resilience. 

Vectors might adapt to new environments and climate. The interaction between dengue virus, the host and the environment is dynamic. Consequently, disease risks may change and shift with climate change in tropical and subtropical areas, in combination with increased urbanization and movement of populations.

Prevention and control

The mosquitoes that spread dengue are active during the day. 

Lower the risk of getting dengue by protecting yourself from mosquito bites by using: 

• clothes that cover as much of your body as possible;
• mosquito nets if sleeping during the day, ideally nets sprayed with insect repellent;
• window screens;
• mosquito repellents (containing DEET, Picaridin or IR3535); and
• coils and vaporizers.

Mosquito breeding can be prevented by:

• preventing mosquitoes from accessing egg-laying habitats by environmental management and modification;
• disposing of solid waste properly and removing artificial man-made habitats that can hold water;
• covering, emptying and cleaning domestic water storage containers on a weekly basis;
• applying appropriate insecticides to outdoor water storage containers.

If you get dengue, it’s important to:

• rest;
• drink plenty of liquids;
• use acetaminophen (paracetamol) for pain;
• avoid non-steroidal anti-inflammatory drugs, like ibuprofen and aspirin; and
• watch for severe symptoms and contact your doctor as soon as possible if you notice any.

So far one vaccine (Denga) has been approved and licensed in some countries. However, it is recommended only for the age group of 6 to 16 years in high transmission settings. Several additional vaccines are under evaluation.

Reference WHO.