Differential Diagnosis

Some of the diseases which can be considered in differential diagnosis are:

(1) Dengue fever: Severe backpain with purpuras or active bleeding might suggest dengue fever. Confirmatory laboratory diagnosis is possible.

(2) Reactive Arthritis: In general, any arthritis that follows a febrile gastrointestinal or genitourinary infection (triggering microbes) is considered a reactive acute inflammatory arthritis if it lasts less than six months . The hallmark feature is enthesitis where collagenous structures such as tendons and ligaments insert into bone are involved. Oral mucosal ulcers are seen.

(3) Serum sickness illness: Polyarthritis may be associated with a serum sickness type reaction caused by vaccine, medication or other viral infections

(4) Rickettsial disease can present with fever, rash and joint pains. Confirm by serology.

(5) Rheumatic fever: More common in the children and presents with fleeting (migratory) polyarthritis predominantly affecting the large joints. Modified Jones criteria should be the basis for diagnosis. Raised ASO titre and a history of recurrent sore throat are other points to be noted.

(6) Malaria: patient can present with high fevers and may also complain of joint pains. Periodicity of fever and alteration of consciousness / seizures should prompt a diagnosis for malaria

(7) Leptospirosis: Severe myalgia localized to calf muscles with conjunctival congestion/ or subconjunctival haemorrhage with or without oliguria or jaundice in a person with history of skin contact to contaminated water would suggest Leptospirosis.

Clinical and laboratory features of chikungunya virus infections compared with dengue virus infections

Chikungunya		Dengue
Fever (>39°C)	+++	++
Arthralgia	+++	+/-
Arthritis	+	-
Headache	++	++
Rash	++	+
Myalgia	+	++
Hemorrhage	+/-	++
Shock	-	+
Lymphopenia	+++	++
Neutropenia	+	+
Thrombocytopenia	+	+++
Hemoconcentration	-	++

Chikungunya and dengue

Difficult to distinguish chikungunya and dengue based on clinical findings alone
Chikungunya and dengue viruses transmitted by the same mosquitoes
The viruses can circulate in the same area and cause occasional co-infections in the same patient
Chikungunya virus more likely to cause high fever, severe polyarthralgia, arthritis, rash, and lymphopenia
Dengue virus more likely to cause neutropenia, thrombocytopenia, hemorrhage, shock, and death
Patients with suspected chikungunya should be managed as dengue until dengue has been ruled out
Proper clinical management of dengue reduces the risk of medical complications and death
Aspirin and other NSAIDs can increase the risk of hemorrhage in patients with dengue