Experts have revealed the critical symptoms of Legionnaires' disease to look out for after millions of Aussies were exposed to the disease over the holiday period.
Millions of people who visited Sydney's CBD over Christmas and New Year are being urged to check for symptoms of Legionnaires' disease after seven people were diagnosed with the potentially fatal lung disease.
NSW Health issued a health alert on Wednesday for anyone who has visited the city center in the last ten days since Christmas Eve, to remain alert for symptoms such as coughing, fever, shortness of breath and headache.
The seven people, four men and three women aged between 20 and 70, have been diagnosed with the debilitating lung disease and admitted to hospital.
They spent ten days at locations in Sydney's CBD, between Bathurst St, Sussex St, Elizabeth St and Circular Quay, before experiencing any symptoms.
Legionnaires' disease can cause serious respiratory infections and pneumonia, which can lead to death in severe cases. Health authorities are now on high alert as fears grow that the disease will continue to spread.
As a growing number of people are diagnosed with Legionnaires' disease, experts have revealed the key symptoms to look out for (pictured, Sydney on New Year's Eve)
Legionella (pictured) is a type of bacteria that typically thrives in large buildings – such as hotels and office buildings – where it grows in the water supply
What are legionnaires?
Legionella is a type of bacteria that typically thrives in large buildings – such as hotels and office buildings – where it grows in the water supply.
It is especially a problem in warm climates, where the heat helps the plant to reproduce.
Swimming pools and dirty air conditioning units are common contamination sites because they can accumulate warm, stagnant water that is dispersed as droplets into the air and then inhaled.
But the bacteria, which occur naturally in fresh water, can also be in showers and taps that have not been used for a few days.
This is why some experts urge vacationers to leave taps and showers open before coming into contact with the water.
What is the disease it causes?
The bacteria itself can cause an infection called Legionnaires' disease.
Millions of people who visited Sydney's CBD over Christmas and New Year (pictured) are being urged to check for symptoms of Legionnaires' disease
What are the symptoms?
Symptoms usually develop between two and ten days after infection, including coughing, difficulty breathing and chest pain.
In severe cases, patients may experience diarrhea and confusion.
However, some patients will develop pneumonia, which can be life-threatening.
Other symptoms may include headache, muscle aches, chills, fever of 104°F (40°C) or higher, nausea, vomiting, and other mental changes.
NSW Health said symptoms can develop up to 10 days after exposure to contaminated water particles in the air.
So far, seven people in NSW have been diagnosed with the debilitating lung disease
How can the disease spread?
It is usually spread by contaminated water particles emitted from a cooling system.
The most common way people contract Legionnaires' disease is by inhaling tiny droplets of water that contain bacteria that cause the infection.
However, under rare circumstances it can be spread through human transmission.
In recent years, an average of 400 confirmed and probable cases of Legionnaires' disease have been reported annually in Australia.
In 2014, the reporting rate was 1.8 cases per 100,000 inhabitants.
A variant of Legionnaires' disease can also be spread through soil and potting soil.
In September, NSW Health said as many as 52 people had been exposed to the disease as a result of inhaling the bacteria from the soil.
How dangerous is it? Can you die from the disease?
Although anyone can get Legionnaires' disease, experts say the infection is not something people should worry about on a daily basis.
The World Health Organization estimates the mortality rate at 5 to 10 percent.
But among people with weakened immune systems, such as patients with rheumatoid arthritis or kidney failure, this can be as high as 30 percent.
NSW Health said those at greater risk of dying from the disease are those with chronic illnesses, people with HIV/AIDS or cancers, smokers, transplant recipients and people over the age of 50.
In recent years, an average of 400 confirmed and probable cases of Legionnaires' disease have been reported annually in Australia (photo, New Year's crowds at Circular Quay)
How is it treated?
Antibiotics are used to treat the condition.
Doctors typically test for the condition using a chest X-ray, and they use a urine test or a mucus sample to discover whether the pneumonia is caused by legionella.
People who are admitted to hospital with the disease – where the disease is normally treated – may be given antibiotics such as doxycycline or put on a ventilator.
There is no vaccine available for those who contract Legionnaires' disease as a result of contact with the bacteria.