Five people have been diagnosed with malaria in Florida and Texas as the potentially-fatal disease spreads across parts of the US.
According to the Centres for Disease Control and Prevention, it is the first time the mosquito-borne disease has been locally acquired in the US in twenty years.
There are now four cases in Florida, and one in Texas, after the disease was discovered in the states over the last two months.
The first case in Florida was diagnosed on May 26 in Sarasota County.
A resident in Texas, who had been working outdoors in Cameron County, was diagnosed on June 23 with the disease.
The agency revealed the patients who were diagnosed "are improving" and responding well to treatment.
On Monday, the CDC said malaria is considered a medical emergency, and anyone with symptoms should be "urgently evaluated."
However, the risk of catching malaria in the US remains low, and most cases are normally picked up when people travel outside of the country.
The health agency said around 95 per cent of malaria infections are transmitted in Africa, and since 1992 there have been only 11 outbreaks involving malaria from mosquitoes in the US.
Eight cases were last reported in 2003 at Palm Beach County, Florida, according to the CDC.
What is Malaria?
The disease is caused by five species of parasite which is carried by female mosquitoes. It can take just one bite to get infected with malaria, according to the NHS.
The infection is very common in certain parts of the world and is found in tropical regions, including:
- large areas of Africa and Asia
- Central and South America
- Dominican Republic and Haiti
- parts of the Middle East
- some Pacific islands
According to World Health Organization (WHO), it is one of the world's biggest killers, claiming the life of a child every two minutes.
Most of the deaths happen in Africa - with 250,000 children dying form the fatal disease each year.
What are the symptoms?
Malaria can be hard to spot, but symptoms include:
- a high temperature, sweats and chills
- headaches and feeling confused
- feeling very tired and sleepy (especially in children)
- feeling and being sick, tummy pain and diarrhoea
- loss of appetite
- muscle pains
- yellow skin or whites of the eyes
- a sore throat, cough and difficulty breathing
These symptoms usually appear between 7 and 18 days after you've been bitten by an infected mosquito.
But sometimes you may not have symptoms for months after travel, and rarely years.
A blood test confirms a diagnosis.
How to avoid getting the disease?
It's important to check the malaria risk for the country you're travelling to before you go.
You're still at risk of getting malaria if you now live in the US but were born or used to live in a high-risk country. You will not be immune to malaria anymore.
If you're travelling to an area where malaria is found, get advice from a GP, nurse, pharmacist or travel clinic before you go.
It's best to do this at least 4 to 6 weeks before you travel, but you can still get advice at the last minute if you need to.
You may be prescribed antimalarial tablets to reduce the risk of getting malaria and told how you can prevent mosquito bites.
Using insect repellent, wearing clothes that cover your limbs and using an insecticide-treated mosquito net can help catching malaria.
How do I treat Malaria?
Malaria is an emergency and needs to be treated quickly. It is normally treated with antimalarial medicines, which usually leads to a full recovery if discovered early.
However, some people will stay in hospital to have specialist care and treatment if the infection is untreated and can result in severe anaemia.
Malaria can sometimes come back and will need to be treated again if this happens.
