DENGUE HEMORRHAGIC FEVER (DHF) AND THE CRITICAL

PHASE: BE AWARE OF THE CONDITION WHEN THE FEVER

STARTS TO SUBSIDE

Written by. Xena Calista

− “Decrease in fever does not always indicate recovery. In Dengue Hemorrhagic Fever, the

critical phase may actually begin when the body temperature returns to normal." −

Dengue Hemorrhagic Fever (DHF) is an infectious disease caused by the dengue virus

and transmitted through the bites of infected mosquitoes, particularly Aedes aegypti. This

disease remains a major public health concern in many tropical and subtropical countries,

including Indonesia. DHF can affect anyone regardless of age, from children to adults. The

severity of the disease also varies, ranging from asymptomatic infections and mild symptoms

to severe conditions that can be life-threatening if not properly treated (WHO, 2009).

Symptoms of DHF generally appear after the virus has undergone an incubation period

of several days. Patients usually experience a sudden high fever, headache, pain behind the

eyes, muscle and joint pain, nausea, vomiting, and the appearance of reddish spots on the skin.

However, symptoms may vary from person to person, so medical examinations are necessary

to confirm the patient's condition. Understanding this disease is important so that the public

does not consider ordinary fever as the only symptom that needs attention (WHO, 2009).

Dengue virus transmission occurs through mosquitoes that act as disease vectors. Aedes

aegypti is one of the main vectors responsible for transmitting DHF to humans. These

mosquitoes generally breed in clean water containers that are left uncovered, such as bathtubs,

buckets, drums, flower vases, and discarded objects that can collect water. Environmental

another person through subsequent bites. Therefore, the presence of infected mosquitoes is an

important part of the chain of DHF transmission (WHO, 2009).

DHF transmission is also influenced by environmental conditions and community

behavior. The habit of leaving water storage containers uncovered, accumulating discarded

objects, and paying insufficient attention to environmental cleanliness can create suitable

breeding sites for mosquitoes. Therefore, mosquito control is not only the responsibility of

healthcare workers but also requires community involvement in maintaining the cleanliness of

residential environments.

Symptoms of DHF may appear suddenly after the dengue virus enters the body and

passes through its incubation period. Fever is one of the most common symptoms, usually

may experience worsening conditions. One important aspect to consider is the change in body

temperature throughout the course of the disease. When the fever begins to subside, patients

should not immediately be considered recovered because this period may coincide with the

beginning of the critical phase (WHO, 2009).

In general, the clinical progression of dengue infection is divided into three phases: the

febrile phase, the critical phase, and the recovery phase. Each phase has different characteristics

and risks. Understanding these phases is essential so that patients and their families can

recognize changes in the patient's condition and know when to seek medical attention

immediately (CDC, 2026).

The febrile phase is the initial stage of DHF, which generally lasts for 2–7 days. During

this stage, patients experience an increase in body temperature that may reach 40°C. The fever

examinations at healthcare facilities are important when dengue infection is suspected,

particularly if the fever is accompanied by other symptoms indicating DHF. Early management

can help reduce the risk of delays in recognizing disease progression (Ministry of Health of the

Republic of Indonesia, 2020).

The critical phase is the stage that requires the greatest attention during the progression

of DHF. This phase usually begins when the patient's body temperature starts to decrease or

returns close to normal, generally around the third to seventh day after the onset of fever. The

critical phase lasts approximately 24–48 hours. During this period, some patients may

experience increased vascular permeability, which causes blood plasma to leak from the blood

vessels into surrounding tissues or body cavities (WHO, 2009; CDC, 2026).

A common misconception among the public is the belief that a decrease in fever indicates

that the disease has been cured. In fact, in DHF, a decrease in body temperature may signal the

beginning of the critical phase. Not all patients will experience severe complications, but this

period must still be closely monitored because changes in the patient's condition can occur

rapidly. Therefore, monitoring should not be discontinued simply because the patient's body

temperature has returned to normal (CDC, 2026).

The recovery phase is the stage when the patient's condition begins to improve after

passing through the critical phase. During this phase, fluid that previously leaked from the

blood vessels is gradually reabsorbed into the bloodstream. The patient's general condition

usually improves, appetite begins to increase, and physical activities gradually return to normal.

The white blood cell count generally begins to increase first, followed by an increase in the

an assessment by healthcare professionals (WHO, 2009).

Dengue Hemorrhagic Fever is an infectious disease caused by the dengue virus and

transmitted through the bites of infected mosquitoes. This disease has three phases of

progression: the febrile phase, the critical phase, and the recovery phase. Among these three

phases, the critical phase requires special attention because plasma leakage may occur,

potentially leading to decreased blood volume, dengue shock, severe bleeding, and organ

dysfunction.

An important point that the public needs to understand is that a decrease in fever does

not always indicate that the patient has recovered. During this period, patients require further

monitoring to identify the possible appearance of warning signs. Medical examinations,

cooperation among individuals, families, communities, and healthcare professionals.

Reference:

Centers for Disease Control and Prevention. (2025, August 26). Clinical testing guidance for

dengue. https://www.cdc.gov/dengue/hcp/diagnosis-testing/

Centers for Disease Control and Prevention. (2026, April 15). Clinical care of dengue.

https://www.cdc.gov/dengue/hcp/clinical-care/

Centers for Disease Control and Prevention. (2026, February 24). Clinical features of dengue.

https://www.cdc.gov/dengue/hcp/clinical-signs/index.html

hk0107menkes98452020

World Health Organization & Special Programme for Research and Training in Tropical

Diseases. (2009). Dengue: Guidelines for diagnosis, treatment, prevention and control.

World Health Organization. https://www.who.int/publications/i/item/9789241547871