When you're bitten by a
malaria-infected mosquito, the parasites that cause
malaria are injected into your blood and invade your liver cells. The parasite
reproduces in the liver cells, which then burst open, allowing thousands of new
parasites to enter the bloodstream and infect red blood cells. The parasites
reproduce again in the blood cells, kill the blood cells, and then move to
other uninfected blood cells.
The time from the initial malaria
infection until symptoms appear (incubation period) generally ranges
- 9 to 14 days for Plasmodium (P.) falciparum.
- 12 to 18 days for P. vivax and P. ovale.
- 18 to 40 days for
- 11 to 12 days for P. knowlesi.
Symptoms can appear in 7 days. Occasionally, the time
between exposure and signs of illness may be as long as 8 to 10 months with
P. vivax and P. ovale, because
these parasites can survive in the human liver for a long time.
The incubation period may be longer if you are taking medicine to prevent
infection (chemoprophylaxis) or have developed partial
immunity due to previous infections.
Malaria can begin with flu-like symptoms. In the early stages, infection
from P. falciparum is similar to infection from
P. vivax, P. malariae, and
P. ovale. You may have no symptoms or symptoms that are
less severe if you are immune or partially immune to malaria.
Common malaria symptoms include:
Symptoms may appear in cycles. The time between episodes of
fever and other symptoms varies with the specific parasite you are infected
with. Episodes of symptoms may occur:
- Every 48 hours if you are infected with
P. vivax or P. ovale.
- Every 72 hours if you are infected with
- P. falciparum does not usually have a regular, cyclic fever.
After the early stages,
life-threatening complications develop rapidly with
P. falciparum and P. knowlesi
and, if untreated, may result in irreversible complications or death.2
If untreated, you may recover in a week to a
month (or longer) after being infected with P. vivax,
P. malariae, or P. ovale.
Malaria can be a very serious disease for a
pregnant woman and her unborn baby (fetus), and for
young children. Medication choices are limited for a pregnant woman or a
child. Infection with P. falciparum can lead to death
for a pregnant woman and her fetus. For these reasons, a pregnant woman should
not travel to an area where she could get P. falciparum
malaria. Visit the CDC Web site (www.cdc.gov/malaria/travel/index.htm) to find
out whether malaria is a problem in the country where you will be traveling.
Malaria caused by
P. falciparum may come back (recur) at irregular
intervals for up to 2 years if treatment is not complete.
caused by P. vivax and P. ovale
may recur at irregular intervals for up to 3 to 4 years, but medication
treatment can prevent relapses.
can remain in the blood of an infected person for more than 30 years, usually
without causing any symptoms.
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