DENGUE – Some Take Home Messages
1) Dengue in Mumbai traditionally appears around July every year and continues in earnest till early December. This season (2016) however, we may see an earlier appearance of the epidemic.
2) Dengue is commoner in the young. Older persons acquire partial immunity over the years. However, in some seasons dengue does not respect age!
3) Dengue virus has four serotypes. Infection with one serotype confers immunity against all four for a few months. The immunity against the infecting serotype is for life. Thus, in one season a person can get dengue only once unless he is very unlucky.
4) Fever in dengue typically lasts less than 7 days. Fever peaks on day 1. This helps differentiate it from enteric fever. Fever is all day long. This helps differentiate it from malaria.
5) The principal ‘localizing symptom’ of dengue is myalgia as against only headache & backache in malaria. Retro-orbital pain occurs often in dengue and is not seen in malaria or typhoid. Arthralgias are common too.
6) For lab diagnosis of dengue, ask for dengue NS1 antigen in the 1st four days of fever and dengue IgM thereafter. IgG is not useful in adults. Paediatricians tend to ask for both IgG & IgM. If both are positive a proneness to complications like DSS or DHF is possible.
7) Rapid card test of dengue IgM are not reliable. Ask for Dengue IgM by ELISA. Elevation of liver transaminases can occur in many fevers. A good clue to differentiate between malaria & dengue is that SGOT is greater than SGPT in dengue & vice versa in malaria.
8) I like to prescribe paracetamol round the clock to dengue pts and not just on an SOS basis. I give 3 gm/day to adults pts, often adding a muscle relaxant.
9) Antibiotics have absolutely no role to play in the treatment of dengue.
10) Leakage from capillaries is an integral part of dengue pathophysiology. This extravasation of fluid contributes to following clinical manifestations-
- Puffiness of face & swellings over limbs.
- Small pleural effusions which manifest as tachypnoea (without dyspnoea) and dry cough.
- ARDS (adult respiratory distress syndrome manifesting as dyspnoea) – can be spontaneous or precipitated by enthusiastic parenteral hydration in hospital.
- Mild ascites – not detectable by standard signs (shifting dullness etc.). An interesting feature of this ascites (a personal observation; not mentioned in books) is rebound tenderness in lower abdomen.
- A rise in haemoglobin.
- A fall in serum albumin.
11) USG can provide ‘circumstantial evidence’ of dengue as it can pick up capillary leak in 3 areas – ascites, pleural effusion and gall bladder wall oedema.
12) The fall in platelet count in dengue continues for about 48 hours after fever has settled. This is often a reason for unnecessary panic! We should not be scared of a platelet count of 10,000 in a proven & asymptomatic dengue patient whose fever has disappeared a day or two back.
13) Leucopenia appears earlier than thrombocytopenia and can be seen as early as day 1 of fever. The polycythaemia & leucopenia of dengue get corrected before the thrombocytopenia does.
14) Dengue is a fascinating disease because every year the virus comes up with some variations in its clinical presentation! In some years a rash is very prominent…in some other seasons there is a palmoplantar pruritus without rash…..and in some years ascites & pleural effusions are seen in every other patient! Itching often occurs after fever disappears.
15) An unfortunate & not infrequent reason for pulmonary oedema (& sometimes death) in dengue patients is parenteral overhydration in hospitalized patients. This happens due to the proneness to extravasation & the tendency of consultants to continue same orders for multiple days (‘Ct all’). I often say that a hospital visit by the family physician on day 3 of hospitalization can save a patient’s life by preventing this. Typically, capillary leak occurs when the fever is receding.
16) The incubation period of dengue can be as small as 2 days. This becomes important when a traveller to India gets fever. If the fever appears at 48 hours after arrival, dengue becomes a possibility but definitely not malaria or enteric fever.
dr. tushar shah
updated on 2nd May 2016