Malaria is a parasite that is transmitted to humans through the
bite of an infected mosquito. There are four species of malaria
parasites: Plasmodium falciparum, P.
vivax, P. ovale, and P.
malariae. These four species differ in their biology and in
severity of disease.
Malaria is the leading cause of death and disease worldwide and
was once endemic throughout much of the United States. During the
civil war, there were over 1.2 million cases of malaria among
soldiers of both sides. In 1933, 30% of the human population in
the Tennessee Valley were infected.
Malaria was rampant in California during the gold rush and early
1900s. In fact, many of the mosquito abatement programs in
California were initially formed to combat malaria.
Today, there are about 1,200 cases of malaria reported in the US
each year, approximately 300 of these (25%) occur in California.
In almost every case, the disease is acquired outside the US in
countries where malaria is common. However, there have been
several occasions in which local transmission has occurred.
Mosquitoes acquire the infection from persons with active malaria
and transmit the parasite to local residents. The most recent of
these occurred in 1974 in San Diego.
What are the signs and symptoms of malaria?
Recurring bouts of high fever and flu-like illness with
shaking, chills, and sweating with headache, muscle aches, and
fatigue
Severe infections with Plasmodium
falciparum malaria can result in coma, renal failure,
convulsions, and death
How can I get malaria?
Malaria parasites are acquired through the bite of an infected
mosquito. Only certain mosquito species of the
genus Anopheles are
capable of transmitting malaria. Because the parasite lives in
the blood, it can also be transmitted through blood transfusions,
organ transplants, contaminated needles, and breast milk.
What is the life cycle of malaria?
Mosquitoes become infected with the malaria parasite by feeding
on the blood of an infected human. The parasites develop in the
mosquito’s gut for about a week before moving to the salivary
glands. Once in the salivary glands, the parasite can move into a
new human when the mosquito acquires its next blood meal.
Malaria parasites move from a person’s bloodstream to the liver
where they multiply and develop. The parasites may remain in the
liver for 1 week to several months. After this, the parasites
enter the bloodstream where they invade red blood cells. This
stage multiplies in the red blood cells, periodically causing the
cells to burst and release more parasites into the bloodstream.
For two of the forms of malaria (P.
ovale and P. vivax), some parasites can
remain in the liver causing relapses months or years after the
person was bitten.
Can I get malaria in San Mateo County?
Malaria is not currently present among mosquitoes in San Mateo
County. However, two of the species of mosquitoes in San Mateo
County are capable of transmitting the
disease: Anopheles hermsi and An.
punctipennis. Local mosquitoes could become infected by
feeding on someone with an active case of malaria. For this
reason, the District works closely with the County Health
Department on malaria cases. When malaria is detected in a
patient in San Mateo County, the health department notifies the
District. District staff will then conduct mosquito surveillance
in the area to ensure that vector mosquitoes are kept at very low
numbers.
What can I do if I am traveling to a country that has malaria?
Medications are available to prevent people from becoming
infected with malaria while traveling. The type of medicine and
the best time to take it is best determined on an individual
basis through consultation with a physician. Ask your doctor for
advice.
