Dengue fever rarely strikes in the United States — the last reported outbreak was in Texas in But if you plan to travel to a foreign country, especially one in the tropics, it's wise to guard against dengue fever.
Wearing insect repellent, covering sleep areas with netting, and avoiding the outdoors at dusk and dawn when mosquitoes are most active can help lower the chances of infection. Dengue fever is caused by four similar viruses spread by mosquitoes of the genus Aedes , which are common in tropical and subtropical areas worldwide. When an Aedes mosquito bites a person who has been infected with a dengue virus, the mosquito can become a carrier of the virus.
If this mosquito bites someone else, that person can be infected with dengue fever. The virus can't spread directly from person to person. In rare cases, dengue fever can lead to a more serious form of the disease called dengue hemorrhagic fever DHF. DHF can be life-threatening and needs to be treated right away. Symptoms of dengue fever are generally mild in younger children and those who have the disease for the first time. Older kids, adults, and those who have had a previous infection may have moderate to severe symptoms.
Dengue fever used to be called "breakbone fever," which might give you an idea of the severe bone and muscle pain it sometimes can cause. The fever isn't actually breaking any bones, but it can sometimes feel like it is. And the number of clot-forming cells platelets in your bloodstream drops.
This can lead to shock, internal bleeding, organ failure and even death. Warning signs of severe dengue fever — which is a life-threatening emergency — can develop quickly. The warning signs usually begin the first day or two after your fever goes away, and may include:.
Severe dengue fever is a life-threatening medical emergency. Seek immediate medical attention if you've recently visited an area in which dengue fever is known to occur, you have had a fever and you develop any of the warning signs. Warning signs include severe stomach pain, vomiting, difficulty breathing, or blood in your nose, gums, vomit or stools.
If you've been traveling recently and develop a fever and mild symptoms of dengue fever, call your doctor. Dengue fever is caused by any one of four types of dengue viruses. You can't get dengue fever from being around an infected person. Instead, dengue fever is spread through mosquito bites. The two types of mosquitoes that most often spread the dengue viruses are common both in and around human lodgings. When a mosquito bites a person infected with a dengue virus, the virus enters the mosquito.
Then, when the infected mosquito bites another person, the virus enters that person's bloodstream and causes an infection. After you've recovered from dengue fever, you have long-term immunity to the type of virus that infected you — but not to the other three dengue fever virus types.
This means you can be infected again in the future by one of the other three virus types. Your risk of developing severe dengue fever increases if you get dengue fever a second, third or fourth time. Because Aedes aegypti require a warm climate, they typically do not live at altitudes above m, where the temperature is colder. These mosquitoes are associated with the living spaces of humans.
They generally spend their entire lives in and around the houses where their eggs hatched. Figure 1: Aedes aegypti Aedes aegypti is the principal vector responsible for dengue transmission. Some rights reserved. Figure 2: Dengue transmission The dengue virus is spread through a human-to-mosquito-to-human cycle of transmission.
Prospects for a dengue virus vaccine. Nature Reviews Microbiology 5, — All rights reserved. The dengue virus is spread through a human-to-mosquito-to-human cycle of transmission Figure 2. Typically, four days after being bit by an infected Aedes aegypti mosquito, a person will develop viremia, a condition in which there is a high level of the dengue virus in the blood. Viremia lasts for approximately five days, but can last as long as twelve days. On the first day of viremia, the person generally shows no symptoms of dengue.
Five days after being bit by the infected mosquito, the person develops symptoms of dengue fever, which can last for a week or longer. How does an Aedes aegypti mosquito become a dengue vector? After a mosquito feeds on the blood of someone infected with the dengue virus, that mosquito becomes a dengue vector.
The mosquito must take its blood meal during the period of viremia, when the infected person has high levels of the dengue virus in the blood. Once the virus enters the mosquito's system in the blood meal, the virus spreads through the mosquito's body over a period of eight to twelve days. After this period, the infected mosquito can transmit the dengue virus to another person while feeding.
Does a mosquito infected with the dengue virus only transmit the virus to the next person it feeds on? No, once infected with dengue, the mosquito will remain infected with the virus for its entire life.
Infected mosquitoes can continue transmitting the dengue virus to healthy people for the rest of their life spans, generally a three- to four-week period. Both male and female mosquitoes feed on plant nectars, fruit juices, and other plants sugars as their main energy source. Why, then, do mosquitoes bite humans? Female mosquitoes require blood to produce eggs, so they bite humans.
Each female mosquito can lay multiple batches of eggs during its lifetime, and often Aedes aegypti take several blood meals before laying a batch of eggs. When a female mosquito is infected with the dengue virus, the virus is present in its salivary glands. How does the virus travel from the mosquito's salivary glands into a human?
When taking a blood meal, an infected female mosquito injects its saliva into the human host to prevent the host's blood from clotting and to ease feeding. This injection of saliva infects the host with the dengue virus.
Are mosquito bites the only way the dengue virus can be transmitted to humans? In rare events, dengue can be transmitted during organ transplantations or blood transfusions from infected donors. There is also evidence that an infected pregnant mother can transmit the dengue virus to her fetus. Despite these rare events, the majority of dengue infections are transmitted by mosquito bites. When Dengue Strikes Twice: When patients are infected with the dengue virus they can come down with dengue hemorrhagic fever and suffer massive internal bleeding and liver damage.
Dengue infection, immunity and mortality: Dengue infection follows development of antibodies which are not protective to the individual. Aug 24, Featured Experts. Sumit Bhatia Senior Consultant —Gastroenterology. Tejnarayan Raj Consultant- Gastroenterology.
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