Algorithm for Management of Common Febrile Illnesses

Algorithm for Management of Common Febrile Illnesses

Prepared by: Drs. Srinivas Kakkilaya, MD (Int. Medicine); Balasaraswathy P, DVD, DNB (Dermatology); Vishnu Sharma, MD (Respiratory Medicine); Shivaprasad B, MD, DNB (Gastroenterology); Mangaluru

In Dakshina Kannada District, and elsewhere too, the incidence of infectious diseases such as malaria, dengue fever, leptospirosis and viral hepatitis increase during the summer and rainy seasons. The new SARS CoV-2 is also spreading now, and all the hype generated about this infection is bound to create fear and confusion in the coming days. Therefore, it is important for clinicians and healthcare workers, as also the general public, to know the differentiating features of these common infections, so as to manage them effectively and to prevent complications and deaths.

We have prepared a simple algorithm for differentiating between these common infections during the first 3 or 4 days of the illness, on the basis of common clinical features and simple laboratory tests that are available in most rural areas and primary health centres. Basic information on clinical course and initial treatment, and indications for hospitalization are also provided.


Any patient having respiratory symptoms such as anosmia, ageusia, cough, sore throat, and rhinitis, with or without fever, must be considered as a COVID 19 suspect and must be asked to stay at home and contact the helpline or the doctor concerned. Patients who have fever but none of the symptoms related to COVID 19 can be considered to have other causes of fever and evaluated clinically and with necessary laboratory tests. Generalised rashes that blanch on pressure, and retro-orbital pain suggest dengue while conjunctival suffusion and severe muscle pains may indicate leptospirosis. Test for malaria and TC, DC, ESR will help further: leptospirosis is associated with neutrophilic leukocytosis and high ESR, and urinary abnormalities; while in dengue fever, WBC count is normal or low. Fever, nausea and vomiting, with ALT more than 350 indicates a possibility of acute viral hepatitis. Malaria is diagnosed with a positive test for malaria parasite.

Clinical Features

COVID 19 passes off as an asymptomatic or mild infection in more than 80-85% of cases. The initial symptoms of COVID 19 have been reported as anosmia (loss of smell), ageusia (loss of taste), cough, head ache, body ache, sore throat, rhinitis, conjunctival redness, and diarrhoea in some. Among the symptomatic patients, fever, usually mild to moderate degree, can develop anytime between first to 3rd or 4th day, preceded by prodromal symptoms mentioned above, and it may be associated with chills in some. Most patients recover in 4-7 days of these symptoms. Reports of severe COVID 19 from different parts of the world have now clearly shown that the median time for development of severe disease is between 7-8 days, and median time for admission to hospitals is 10-11 days. Age beyond 60-65 years, hypertension, type 2 diabetes mellitus, COPD and other chronic lung disease, chronic renal and hepatic disease, cancers, immunocompromised state have been identified as risk factors for severe COVID 19 and almost all the published reports have indicated that more than 90-95% of deaths due to severe COVID 19 have happened in patients with one or more of these co-morbidities.

SARS CoV-2 is highly infectious, and is now known to be transmitted from direct contact with even asymptomatic cases of COVID 19, and from various surfaces contaminated with infected secretions. Patients with severe COVID 19 are more infective, and for longer time. There is no evidence yet of airborne transmission of SARS-CoV2. Considering these, all patients with symptoms of COVID 19, namely, anosmia, ageusia, cough, sore throat, rhinitis, with or without fever, must stay at home, and seek advice through helpline, because traveling to clinics or hospitals will increase the chances of spreading to the community. Patients with fever continuing beyond a week or increasing, worsening or changing cough, or breathlessness, and patients with higher risk for severe COVID 19, must be under the watch and if arrangements could be made, such patients should be examined at their houses by a mobile unit, checking for their clinical condition, and pulse oximetry for oxygen saturation. Patients with SaO2 of ≤94%, at rest or after 6 minutes exercise test, and those who are visibly ill, must be admitted in a dedicated facility.

Dengue fever and leptospirosis manifest with fever, body ache and head ache. Retro orbital pain has been described as a common symptom of dengue fever. In leptospirosis, severe pain over the lumbo sacral region, calf muscles, and abdominal muscles, with tenderness of these muscles, is common. In dengue, the fever is biphasic; after 3 days, the fever subsides, and may reappear after a day or two, to last for another day or two; the total duration of the illness being about a week. During the 3rd and 4th day, if the plasma leakage is significant, complications such as dengue haemorrhagic fever and dengue shock syndrome can occur; this is heralded by rising haemoglobin/PCV levels. In leptospirosis too, the fever is biphasic; the initial febrile phase lasts 2-9 days, and during the second phase, complications such as hepato-renal syndrome, meningitis, pulmonary syndrome etc., can develop.

Malaria commonly presents with fever and head ache; fever can be initially quotidian, and can develop into a classical tertian or subtertian pattern soon after. A dry cough may be present in some cases, particularly P. vivax malaria. The fever subsides in 48 hours after starting anti malarial treatment.

Acute viral hepatitis manifests with fever, nausea, vomiting, during the first few days, and thereafter, as these symptoms subside, patient develops jaundice and high colored urine.

Skin Rashes

Skin rashes are common and characteristic of dengue fever. Initially, a macular, erythematous, blanching rash is seen over limbs and trunk and later, by day 3 or 4, a maculopapular erythematous rash with islands of normal skin sparing (“Islands of white in a sea of red”) may be seen.

Skin rashes have been reported in some, particularly young aged, patients of COVID 19. Widespread urticaria, erythematous rash and varicella-like exanthem have been reported during the initial phase, and later on, after 5-6 days, ischemic and ecchymotic acral lesions have been reported. These later lesions have been reported to be indicators of severe COVID-19.

Rash in Dengue Fever

Rash in initial and later stages of COVID 19

In leptospirosis, a transient petechial rash that can involve the palate, lasting less than 24 hours has been reported occasionally. In some severe cases, petechial rashes may be seen.

Rashes are rare or absent in malaria and viral hepatitis.


Conjunctival suffusion is an early and classical manifestation in leptospirosis, and some cases may also have subconjunctival haemorrhages. Subconjunctival haemorrhages may be seen in dengue fever too. In COVID 19, conjunctival redness has been reported in some cases, particularly in early stage, even before the onset of fever.

Yellowish discoloration of the sclera, due to jaundice, is seen in viral hepatitis, in severe cases of malaria and in severe cases of leptospirosis.

Laboratory Tests

Total WBC Count

The total WBC count is usually elevated in leptospirosis, with neutrophilia. In dengue, malaria, COVID 19 and viral hepatitis, the total WBC count is usually either normal or lower than normal.

Differential Count

Leptospirosis cases have leukocytosis with neutrophilia. In COVID 19, lymphopenia has been widely reported, and lymphocyte counts <20% or <1000/mm3 may indicate severe disease.


In dengue fever, haemoglobin level should be tested to assess the severity of plasma leakage; rise in haemoglobin and/or PCV by 20% or more compared to the baseline value or age/sex related normal value by day 3 and 4 indicates significant plasma leakage. A sudden drop in haemoglobin, coupled with rising levels of ALT may be suggestive of haemophagocytic lymphohistiocytosis, a rare but serious complication of dengue fever, and such patients need to be admitted immediately and referred to a physician or a haematologist.

Anaemia is one of the known complications of severe malaria and may require blood transfusion.

Haemoglobin levels are usually normal in COVID 19, leptospirosis and viral hepatitis


Platelet counts are usually low in dengue, malaria and leptospirosis, and thrombocytopenia may or may not indicate severe disease in these infections. Platelet counts are reported to be normal in COVID 19 and viral hepatitis.


In leptospirosis, the ESR is significantly raised (>60mm). In COVID 19, dengue, malaria and hepatitis, ESR may be normal or variably elevated.


Urinary abnormalities such as albuminuria and presence of leukocytes and red blood cells are invariably seen in leptospirosis. Urine analysis is usually normal in COVID 19, dengue and malaria; however, in severe disease, it may show abnormalities. In viral hepatitis, urobilinogen/ bilirubin may be increased.


In viral hepatitis, ALT is commonly raised above 350IU; in COVID 19, dengue, malaria, leptospirosis it may be normal or may show a mild to moderate increase.

Test for Malaria

Cases suspected to have malaria, and not having COVID 19 like illness, must be tested for malaria parasites.

Initial treatment and Indications for Hospitalization

All cases with symptoms of COVID 19 are instructed to stay at home, so as to prevent spread of the infection in the community. Within the house, they must take all the precautions to isolate themselves so as not to spread the infection to their family members. As more than 95% of cases of COVID are mild and self limiting, they do not need any treatment other than paracetamol for high fever. Patients with high risk of severe COVID 19, patients with continuing or worsening fever even after 6-7 days, increasing cough, and breathlessness should immediately contact their doctors or the helpline and get hospitalised if so advised.

Dengue fever is a mild illness in most of the patients and only in cases of high fever, paracetamol can be taken. Patients with severe malaise, postural giddiness, high grades of fever, persistent vomiting or symptoms such as bleeding must seek admission in hospital.

All confirmed cases of malaria must be treated as per the protocol. Patients with persistent vomiting or symptoms and signs of severe malaria need to be admitted in the hospitals.

The first phase of leptospirosis usually passes of as a non specific febrile illness. In an endemic area, if it is detected, it should be treated with Doxycycline 100 mg twice a day for seven days for non pregnant adults. Pregnant and lactating mothers should be given capsule ampicillin 500 mg every 6 hourly. Children <8 years can be treated with Amoxycillin/ Ampicillin 30-50 mg/kg/day in divided doses for 7 days.

Indications for hospitalisation

In general, any patient with hypotension, hypoxia, tachycardia, tachypnoea, altered sensorium, severe malaise, dehydration or poor performance status should be hospitalised

In COVID 19, patients with increasing fever, worsening cough, breathlessness, SaO2 ≤94% (usually on day 6-7) and patients with risk factors such as hypertension, diabetes, obesity, chronic renal or liver disease, cancers, immunosuppression may need hospitalisation.

In dengue fever, rise in haemoglobin/PCV by ≥ 20%, bleeding, hypotension (usually at day 4-5) need hospitalisation. Rising ALT and sudden drop in haemoglobin may indicate HLH, and will need immediate hospitalisation.

All cases of severe malaria (cerebral, ARDS, renal etc., usually developing by day 4 or later) and patients with persistent vomiting need to be admitted.

In leptospirosis, severe cases with hepato-renal syndrome, meningitis, altered sensorium, GI bleeding, haemoptyisis should be hospitalised.

Patients of viral hepatitis with incessant vomiting and with signs of hepatic failure (rare) need hospitalisation.

Updated: May 13, 2020


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