April 11, 2024 Author: Saraiva da Cunha It is estimated that around 390 million people are infected with the dengue virus every year and that the disease is responsible for 500,000 hospitalizations and 20,000 deaths worldwide. Countries affected by dengue are mainly those in the eastern Mediterranean, Southwest Asia, Africa, Central and South America and the Western Pacific. Although dengue is an old disease, it became a public health concern mainly after the Second World War due to the concentration of the population in urban areas, often with poor sanitation conditions and measures to control mosquitoes. Globalization, lack of awareness about prevention measures and climate changes have been identified as the main factors responsible for the disease expansion over the last decades. Cause and transmission of dengue Dengue is a viral infection that is transmitted to people through mosquito bites . It is caused by dengue virus (DENV), which belongs to the Flavivirus genus and has 4 serotypes (DENV1 to DENV4). All serotypes can infect humans, but DENV2 appears to be the most important. Infection with one of the serotypes protects against a new infection with the same serotype, but not with another type of dengue virus. Aedes aegypti mosquitoes are the main transmitters of dengue fever. They preferably live in tropical areas, in human habitats, lay eggs in natural or artificial water accumulations and fly short distances. Aedes albopictus is another species that may be involved and that also lives in temperate climate zones. The mosquito females need to feed on blood to complete their life cycle. They eat their blood meals mainly during the day, and can bite several people in the same meal, sometimes without being felt. If they are infected with dengue viruses, they can transmit the infection when they bite for food; When they feed on infected people, they can become infected and transmit the disease to other people. Dengue symptoms In around 80% of first dengue virus infections there are no symptoms or there is only a mild fever. When the dengue has symptoms, they have a varying severity, which mada possible to distinguish 3 types of disease according to the 1997 classification of the World Health Organization (WHO): Dengue fever, which is the most common. It is generally self-limited and is associated with a low mortality rate (less than 1% of cases). Symptoms begin 4-10 days after infection (incubation period) and last for 2-7 days, and may be: High fever; Headaches; Muscle and joint pain; Nausea and vomiting; Skin rash. The two most serious forms of dengue: Are the hemorrhagic dengue fever, in which the fragility of the blood vessels favors hemorrhages, and dengue shock syndrome, which results from the evolution of the previous one. Occur in around 1% of infections. Can give rise to complications, including ocular, neurological and cardiovascular. Are more common in a subsequent infection with another serotype and also in children. In 2009, the WHO revised the dengue classification to facilitate triage and management of dengue patients, considering three forms: Dengue without warning signs (which does not require hospital admission); Dengue with warning signs, such as persistent vomiting, abdominal pain, mucous membrane bleeding, lethargy or irritability; Severe dengue, which includes hemorrhagic and shock forms. Dengue treatment and prevention Early diagnosis , development of vaccines and vaccination of populations in countries where the disease is most prevalent, raising awareness for the disease , protective measures and mosquito control are important. There is no specific antiviral therapy for dengue. Treatment aims to alleviate symptoms, and includes medication, supportive measures, and rest. In severe cases, hospitalization is required. Although vaccines against dengue area already available in several countries and there are also other vaccines in different stages of development, the dengue prevention is based mainly in measures to control the mosquito population and in individual care. Avoiding contact with mosquitoes is particularly difficult in the case of dengue, due to the activity of female Aedes aegypti during the day, especially at dawn and dusk, as happens with other species. Therefore, in countries where there is dengue fever it is important to: Avoid going outside when mosquitoes are most active. Use protective nets on windows. Use fans and air conditioning because insects move away from the wind. Choose clothing carefully to cover areas of body when outdoors, using socks and shoes, long sleeves, long pants and a hat. Apply insect repellents to all exposed skin (except around the eyes and mouth) and also to clothing, always following the product's instructions, particularly regarding the age range of people on which they can be used. Eliminate any accumulated water near homes, including swimming pools, buckets of water, potted plant dishes, puddles, among others, as these are the places where female mosquitoes lay their eggs. Sources: Khan MB, Yang ZS, Lin CY, et al. Dengue overview: An updated systemic review . J Infect Public Health 2023;16:1625-42. Parveen S, Riaz Z, Saeed S, et al. Dengue hemorrhagic fever: a growing global menace . J Water Health 2023;21:1632-50. Paz-Bailey G, Adams LE, Deen J, et al. Dengue . Lancet 2024;403:667-82. Meet the Infectious Diseases clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
