Symptoms & severity
P. vivax is associated with ongoing illness as well as death in severe cases. Repeated illness reduces school and work attendance, hindering educational attainment and contributing to poverty.1
P. vivax malaria can cause uncomplicated or severe illness.
Symptoms of uncomplicated P. vivax malaria
- In the uncomplicated form of the disease, initial non-specific symptoms appear, including fever with chills, headache, muscle pain (myalgia), nausea, vomiting, appetite loss and arthralgia (joint pain).
- After 48 h of the blood-stage phase of the infection (see P. vivax lifecycle), a characteristic sudden onset of fever can occur on the third day.
- Stages include a cold stage which lasts from 15–60 mins with shivering, a hot stage which presents with a fever ≥39°C lasting 2–6 hours associated with flushing, dry skin, headache, nausea and vomiting and a sweating stage with fever resolution, profuse sweating and symptom relief lasting 2–4 hours.
Clinical presentation, however, is variable and cannot be used for diagnosis of malaria or the determination of the Plasmodium species. Only diagnostic testing can ascertain the presence of the disease (see How is P. vivax diagnosed?).
Symptoms of severe P. vivax malaria
- Symptoms of severe vivax malaria include: impaired consciousness, respiratory distress (acidotic breathing), multiple convulsions, prostration, shock, pulmonary oedema (radiological), abnormal bleeding and jaundice.
- The criteria for severe vivax malaria are similar to those for adults and children with severe P. falciparum malaria. The main difference is that for P. vivax malaria, there is no parasitaemia density threshold or hyperparasitaemia required to confirm severe malaria.2 This is because severe P. vivax malaria can occur at lower parasite densities than severe P. falciparum malaria.
Over 25 studies have documented species-specific numbers of severe disease and death and noted that the median case fatality rate for P. vivax malaria among inpatients with severe disease was about 3.1%.3