Dengue Fever Information

For people who live, work or travel extensively in the tropics
Especially those who have had Dengue and are worried about getting it again,
as subsequent infections can have a much more severe reaction

By Art Ludwig, from an interview with Enid Garcia, Center for Disease control, Puerto Rico, Jan 11 2003

Summary: Dengue hemorrhagic fever is not particularly difficult to treat, nor that dangerous if your treatment is good. This document describes hard to find info for good monitoring and treatment. Print it out and take it with you to areas where dengue is endemic, for peace of mind to and as a quality control checklist for proper treatment in of dengue. Please link to this page to make it easier for others to find.

Lots of bug bites in the photo above-one of these might be the very mosquito bite from which I contracted dengue fever.

My wife and I came down with Dengue fever while working on water, sanitation and health care for an  Indigenous community in Michoacan, Mexico.

Search on the internet and it is easy to find out that if you've had dengue before, you're at higher risk for contracting dengue hemorrhagic fever (DHF) and dying a gruesome death.

Numerous authorities give the excellent, but difficult to follow advice that boils down to:

"...avoid getting bit by the dengue transmitting mosquito."

Well...the dengue mosquito bites primarily during the day, but if it's still hungry, it will bite at night, too. So, unless you leave and never come back, or you're in a bee keeping suit with DEET all over it, day and night (unlikely, considering most places where there is dengue it is hot), there is a good chance you might get bit again.

So what to do—short of never living in/ visiting/ working in any tropical place ever again?

What if you do get bit again, despite precautions?

It was very difficult to find out what the actual odds of getting DHF are, and what to do if you do get dengue again. A few days search was almost fruitless, until I reached Enid Garcia at the Center for Disease control in Puerto Rico. In stark contrast to the other sources, she is a veritable font of excellent, practical information and advice.

Here's some general info on dengue, followed by the information she shared with me:

General info on Dengue

Dengue is the most important mosquito-borne viral disease affecting humans; its global distribution is comparable to that of malaria, and an estimated 2.5 billion people live in areas at risk for epidemic transmission (1997 numbers).

Each year, tens of millions of cases of dengue fever occur and, depending on the year, up to hundreds of thousands of cases of DHF. The case-fatality rate of DHF in most countries is about 5%; most fatal cases are among children and young adults.

Dengue and dengue hemorrhagic fever (DHF) are caused by one of four closely related, but antigenically distinct, virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4), of the genus Flavivirus. Infection with one of these serotypes does not provide cross-protective immunity, so persons living in a dengue-endemic area can have four dengue infections during their lifetimes.

(Note: it is the subsequent infections which are much more severe)

Dengue is primarily a disease of the tropics, and the viruses that cause it are maintained in a cycle that involves humans and Aedes aegypti, a domestic, day-biting mosquito that prefers to feed on humans. Infection with dengue viruses produces a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. Important risk factors for DHF include the strain and serotype of the infecting virus, as well as the age, immune status, and genetic predisposition of the patient.

Much more general info on Dengue

Dengue symptoms

Once an infected mosquito has bite a susceptible person, the virus has an incubation period of about 4 - 7 days in the body, prior to the development of symptoms. Dengue may produce very mild or severe illness. The disease is characterized by sudden onset of fever (at or over 38°C during the first 3 to 5 days), headache, general malaise, bone pain, and muscular pain. Also some people may present with vomiting or diarrhea, a generalized rash and in some persons, hemorrhagic manifestations that are usually very mild. The symptoms may last from 5 to 7 days. A small proportion of patients may develop low platelets, low blood pressure and severe bleeding requiring hospital care (Dengue hemorrhagic fever or DHF).

What are odds of getting and dying of hemorrhagic or shock dengue if you've had dengue and you get it again?

• DHF usually results from a second infection from a different serotype
• The theory is that antibodies that prevent reinfection by one serotype somehow help other serotype viruses do worse damage
• Most DHF cases are secondary infections. About 90 % of DHF patients have a previous history of dengue (secondary infections). But even if you have a second infection it does not mean that you will develop DHF. Usually 10- 12.5% of secondary infections develop DHF
• Your risk of dying from DHF with inadequate treatment is 10--15%
• Your risk of dying with adequate treatment is less than 1%, regardless of age group.
• In the majority of cases, the actual cause of death is dehydration from loss of plasma volume, not the hemorrhage itself.

The causes of death from DHF by rank (these are causes of poor prognosis of dengue)

1. Shock due to dehydration

2. Severe Hemorrhage

3. Encephalitis

4. Hepatic failure

 

Precautions for people who've already had dengue

If you are returning to a dengue area after already having had dengue, you're at greater risk.

• Avoid getting bit

• Research beforehand a physician, clinic, or hospital which you trust to give you adequate treatment should you develop DHF.

• If you are in endemic areas as part of a development program and you're far from major medical care (as we are), see if you can include part or all of the elements of a "dengue mini-clinic" in your program (see below) so you can monitor your own or other dengue cases locally.

Small dengue clinic list

This list is of equipment for monitoring for possibly emergent DHF in a non-hospital setting, to determine if hospitalization is necessary or not:

• CBC Counter (for WBC, Hematocrit, and platelet count)
• Sphygmomanometer (for blood pressure monitor)
• Thermometers (for children, adults)
• Syringes
• IV fluids & setup: Normal saline solution
• Ring Lactate

Monitoring dengue patients for onset of DHF

Usually people who develop DHF do so after the fever goes down. It is most critical to monitor closely during the 24-48 hours after the fever goes down. In mild cases of DHF changes in vital signs are minimal and transient, patients recovering spontaneously or shortly after a brief period of time. In more severe DHF cases the disease might progress rapidly into a stage of shock. If you can, get a platelet count, blood pressure, and hematocrit at the onset of regular dengue symptoms, as a baseline.

• Hemorrhage, decrease in blood pressure, declining platelet count, or increasing hematocrit are all warning signs that DHF may be developing and you should head towards your medical backup/ hospital.
• If you're far from hospital, go early. Don’t wait.
• If you have any hemorrhage look for medical assistance. Hemorrhage by itself does not mean you will be hospitalized. Your physician needs to evaluate you.
• You can have dengue and mild hemorrhage without it being considered DHF.
• Typical hemorrhage is nosebleed, gum bleed, small red dots in skin (pitequeas), and vaginal bleeding. Less common is vomiting blood.
• Transition from dengue to DHF can happen pretty fast (hours, not days), so make sure to be prepared to respond in case of clinical deterioration.

Patient follow up

• Attend to the patients overall state of well-being
• Check and close monitor blood pressure. If it is falling, then probably more fluid is needed possibly IV.
• Dehydration —Main characteristic of DHF is that people dehydrate faster, through capillary leakage. The fluid may collect in places other than the arteries and veins, such as lungs and abdomen.
• Get hematocrit, platelet count when symptoms/fever starts for baseline.
• Keep monitoring daily. If it goes up by 20% from what they had, this suggests dengue hemorrhagic fever, but don't want to wait this long.
• Do daily/ 2x daily hematocrits, if increasing could indicate leaking of the capillaries.

Criteria for hospitalization

• Increasing hematocrit
• Platelet count --less than 100,000mm3
• Any spontaneous bleeding
• Any warning sign for shock ( see shock related symptoms)
• If not adequately treated, dehydration is what kills people (shock from loss of fluid), not the hemorrhage.
• Give a lot of oral fluids and IV fluids without overload
• Can hydrate adequately just from drinking in most cases

Shock related symptoms

Dengue shock symptoms which indicate that the patient should go to a hospital immediately:

• Clinical deterioration
• Severe abdominal pain as dominant symptom (worse than headache, pain in bones)
• Change in mental status-does not respond, loses sense, can't wake up.
• Drastic change in temperature (cold, clammy or mottling skin)
• Severe vomiting
• Not passed urine in 4 – 6 hours

If you have the equipment & know-how, it could benefit a severely dehydrated patient to provide IV fluids during transport if it is a long way to the hospital.

Testing

You need to send blood to a well-equipped laboratory for dengue testing.

Virologic testing

Virologic testing (to see which of the four serotypes of dengue you've got) has to be done during the acute stage (1-5 days) of the illness to isolate the virus. Afterwards it won't be easy to determine which serotype it was.

The public health service in some countries do virologic analysis by area and outbreaks. Thus, if you've been infected, you might be able to find out the likely serotype by asking around, even if it is too late to test yourself.

Serologic testing

Serologic testing is to see if you have develop antibodies against dengue virus. This will let you know your risk factor for subsequent infections.

IGM testing will give let you know if you've had dengue or not, within 30 days of infection.

IGG testing will let you know if you had dengue in the past (long term immunity)

If you think (or know) you've been exposed to dengue years before, IGG testing will show if you still have the antibodies, and thus are at greater risk of contract DHF from a subsequent infection—this is the most critical information.

Infants exposed to antibodies via pregnancy or mothers milk

• An infant who has been exposed to antibodies through pregnancy or mothers milk and still has them will react exactly the same as somebody who had dengue before. Maternal antibodies usually last up to 6 months or more.
• You can do an IGG test for infant, to determine. If your baby has antibodies or not.
• If a baby tests positive for IGM, they had their own direct infection.
• Not all babies get IGG from breast milk.
• If they test negative for IGG, they will respond to a subsequent dengue infection as an initial infection, not as a more dangerous second infection.
• Retest the baby six months after breastfeeding stops to see If he has own immunity, usually mom's antibodies only last 3-6 months.
• Classic dengue is generally milder in young people. But the risk of DHF increases in infants (less than 1 year) due to the presence of maternal antibodies. Risk of fatality from DHF with adequate treatment is similar across different age groups.
• More children contract dengue, because they have not been exposed to the virus previously and are susceptible.

At the hospital

Should you fly to a hospital in an industrialized country?

The care for dengue is relatively simple, and hospitals in endemic areas are probably more experienced with dengue than most hospitals in overdeveloped countries.

If the facility is reasonable, the personnel reasonably competent, and the patient reasonably happy, it's probably best to stay put.

An ideal situation might be a local hospital close to an airport.

Adequate follow up in a hospital (or small dengue clinic If there is no alternative):

• Frequent (daily or twice daily) platelet count, hematocrit, blood pressure.
• Adequate but not excessive hydration, IV If necessary.
• Monitoring of patient well-being

Before discharge

• Platelet count
• Must have stable or increasing platelet count higher than 50,000
• (below 50,000 risk of spontaneous bleeding is higher)
• Blood pressure
• Stable blood pressure (shows good hydration)
• Hematocrit
• Stable or falling (indicative of no or improvement in capillary leakage)
• Pass 48 hours without fever
• No vomiting
• Doesn't have respiratory distress
• From fluid in lungs.
• Improved general constitution

Good luck!

See also:

Indigenous community Information on our work in Michoacán, Mexico. Re-routing greywater from mosquito breeding puddles in the street to fruit tree irrigation, for example, reduces dengue among many other benefits.

Oasis greywater-book Our book on greywater systems; useful for reducing mosquito habitat.

Water Storage-bookOur book on water storage; useful for reducing mosquito habitat.

Water testing-downloadOur download on all aspects of water quality testing.

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