There has been wide variation in symptomatology and presentation of cases of malaria. Clinical presentation depends upon immune state of the host and the degree of parasitemia. Children with no immunity tend to suffer serious manifestations while those with immunity have fewer symptoms inspite of heavy parasitemia. Malaria in children differs from that in adults in terms of varied manifestation and higher mortality especially under the age of 5 years. Incubation period varies from 7 days to 8 months .. Incubation period for plasmodium vivax is 10-18 days, P.ovale and P.malariae 11-16 days and P.falciparum 7-14 days. When malaria is induced by blood transfusion of parasitised blood, the incubation period varies from 10hours to 60 days.

Prodromal symptoms include generalised weakness, malaise, headache, body ache, loss of appetite, nausea, vomiting and irregular fever. Fever is a cardinal symptom of malaria though it may be absent in congenital and neonatal malaria. Classically it is described as paroxysmal high fever with chills with varying intervals in between episodes. There are no typical characteristics of fever in children. P.falciparum often presents with continuous fever

Fever often has 3 stages :

Cold stage :
High grade fever appearing suddenly with chills and followed by rigors lasting for 15 minutes to 1 hour. Inspite of high fever patient feels cold and tries to cover himself with warm clothes and may be associated with headache, dry skin, cyanosis. Convulsions may be seen particularly in children

Hot stage :
Patient feels hot and throws away the clothes he had put on in previous stage, the face becomes flushed and eyes become red. This stage lasts for 1-8 hours.

Sweating stage :
Fever comes down on its own with profuse sweating and patient feels better and comfortable. Other symptoms include pain in abdomen, intense headache, nausea, vomiting, diarrhoea, generalised body ache, urticaria, myalgia and behavioural changes.

Every organ may be involved in malaria and hence symptoms are varied. Complications include Cerebral malaria associated with convulsion, altered consciousness, delirium and deep coma and may be associated with deep jaundice, anemia, herpes labialis, uremia etc. Respiratory symptoms like cold and cough are common and simulate viral infection. Therapeutic responses is evident in terms of control of respiratory symptoms. Other common systemic manifestations include jaundice, mimicking viral hepatitis. However, in viral hepatitis, fever rarely persists beyond few days and liver enzymes are markedly elevated whereas in malaria high fever is persistent with mild increase in bilirubin (5-10 mg%) and SGPT (200-300 units/dl). Malaria may also present with hemolytic jaundice associated with severe anemia, increased reticulocyte count and decreased platelet count. Other less common manifestation include renal dysfunction, diarrhoea, hypoglycemia, acidosis, thrombocytopenia and DIC. Thus malaria is a multisystemic disease with multi-organ involvement. Splenomegaly is not a pre-requisite for diagnosis as it is often absent in P.falciparum infection and also in early stages of disease. Firm, large spleen indicates repeated or chronic infection or tropical splenomegaly syndrome.

Neonatal malaria or congenital malaria may present with progressive pallor and hepatosplenomegaly without fever. Congenital infection manifests within 2-3 weeks after birth whereas acquired infection presents at 4-6 weeks. History of maternal infection and raised IgM antibodies favour diagnosis of congenital infection. Acquired infections are much more common in highly endemic areas. Following table gives the difference between falciparum and non-falciparum malaria as well as various complications seen with complicated severe falciparum malaria.

Features	Non-Falciparum Malaria	Falciparum Malaria
Incubation period	10 to 18 days	7-4 days
Prodromal symptoms	More prominent	Less prominent
>Fever	>Usually intermittent with typical periodicity	>May be continuous or remittent or even absent. Typical periodicity uncommon
>Feeling of well being after fever is over	>Observed	> Notseen
>Headache	>Absent in between paroxysms	Persistent headache common
Sweating	Fever comes down with profuse sweating	Uncommon
Anemia	Late feature	Early feature
Toxic look	Usually absent	Common
Jaundice	Rare	Not Common
CNS symptoms e.g. delirium	Rare	Not common
Duration of infection	3-4 yrs. in P.vivax and P.Ovale. Many years in P.malariae	Usually < 1 year
Mortality	Rare	Common
Response to Chloroquine	Usually responds well	Chloroquine resistance common
% parasitemia	Usually < 1%	Usually > 2% could be even up to 35%
Slide positivity	Easier to detect as present in peripheral blood	Difficult to detect as present in capillaries of internal organs