Even the name of the virus - and the disease it causes - can be confusing.

"COVID-19", or "coronavirus disease" refers to the illness.

The virus is called "severe acute respiratory syndrome coronavirus 2" or "SARS-CoV-2".

In bushfire zones, most of us learnt a lot - and quickly - about what phrases like "fire behaviour" and "predicted spread" meant.

Now it's time to do the same with common health phrases, so we can all stay informed (but not alarmed).

Here are some of the most common confusion-causing words.

An epidemic is a sudden increase in the number of people with an illness. It occurs in a small population - for instance, a primary school may have a chicken pox epidemic, when many more kids than usual get sick.

A pandemic is a global epidemic - to stick with the chicken pox metaphor, there would be a chicken pox pandemic if primary schools all over the world had a large rise in the number of kids with chicken pox.

The key difference is the scale.

Both epidemics and pandemics spread quickly and affect a large number of people.

An epidemic is contained in a small geographic location.

A pandemic is an epidemic that has spread worldwide. COVID-19 is a pandemic.

Morbidity is the number of people in the population with a disease - for instance, the morbidity rate for asthma in Australia is one in nine, or just over 10 per cent of the population.

As a fraction, it's expressed as number of people with the disease over the total population.

Morbidity rates can give us an idea of how many people are affected by a disease, and how fast it is spreading.

The accuracy of morbidity figures can be affected by testing.

If few people are tested for a disease, but a large percentage of those tested return a positive result, it may appear morbidity in the general population is low.

The more people are tested, the more reliable the figure.

We don't have a good idea of what the morbidity rate of COVID-19 is once it has begun to spread through the general population.

We do know it appears to be higher in the elderly - they are more likely to catch it.

Mortality is the number of people who are killed by a disease. Asthma kills about 400 Australians a year - a mortality rate of 1.5 per 100,000 of the general population, or 1 per 7,000 asthma sufferers.

The accuracy of mortality rates for sick populations can be affected by testing.

If the only people who get tested for a disease are those who are sick enough to go to hospital, the illness may appear more deadly than it really is.

Mortality rates may also be affected by the demographics of the population - a population with more young, healthy people will have a lower mortality rate than a population with more old or unwell people.

The best estimate out of China is a mortality rate of about 3 per cent for COVID-19.

The rate reported in Italy is just under 7 per cent. It is higher in the elderly - reaching almost 15 per cent in those aged 80 and over.

Bacterial infections are caused by single-celled organisms, which reproduce by dividing in two. They can be treated with anitbiotics. Antibiotics work by killing the bacteria, or stopping them multiplying.

Viral infections are caused by particles so small they don't have a cell.

They reproduce by inserting their DNA into the cells of the host organism. Because they are so different from bacteria, antibiotics can't kill viruses. Immunisations are the best way to manage viruses.

They expose the body to a small amount of inactive virus, so the body is prepared to defend against it in future.

COVID-19 caused by is the virus SARS-CoV-2 - antibiotics will not work.

The spread of both bacterial and viral infections can be reduced by hand washing, regularly disinfecting surfaces that are touched often, and staying home if you are sick.

Using hand sanitiser is not the same as hand washing with soap. Soap removes particles by making the surface of your skin too slippery to stick to. Thorough hand washing will remove all kinds of bacteria and viral particles. Hand sanitiser kills germs, but may not get all of them. Some germs may develop a tolerance to hand sanitiser. It is a good option if you are unable to wash your hands with soap and water after touching a communal surface.

You may have heard the term "flatten the curve" bandied about. The curve it's talking about is how the spread of COVID-19 through the population over time looks on a graph.

A rapid spread - or big curve - is what is likely to happen if we don't work to slow the progress of the virus.

It represents a scenario where lots of people get the virus at once.

This would put a lot of pressure on our hospitals and health infrastructure, and possibly cause more deaths, not because the illness is worse, but because people would not be able to get access to the health care they need.

It could also lead to a rise in complications from other health conditions, if people with illnesses that require lots of management can no longer get the care they need.

A slow spread - or flat curve - is what will happen if we take action to slow the spread of the virus.

The same number of people will get sick, but over a longer period of time. It gives hospitals a better chance of managing the extra workload, and will likely result in less preventable deaths.

"Social distancing" is another term being thrown around at the moment.

It's a way to help slow down the spread of the virus - to flatten the curve.

It refers to a range of behaviours, like working from home, staying at home if you feel unwell, avoiding large gatherings and crowded communal spaces, like public transport.

Because COVID-19 is passed from person to person (instead of through contaminated food, water or parasites) human contact gives it opportunities to spread.

The more people are together at the same time, the greater the potential spread. The less opportunities we give it, the more slowly it travels through the population.

Even if you don't feel sick, social distancing is still important. Some people with the virus won't have any symptoms, and won't know they need to self isolate. Social distancing reduces your risk of picking up the virus from one of these carriers.

If you are one of these carriers, it reduces your chances of unknowingly passing the virus on to others.

Symptoms of COVID-19 are very similar to a normal flu - after all, they're related.

People who have symptoms like a fever, cough, breathing difficulties and shortness of breath should isolate themselves. Whether it's COVID-19 or an ordinary flu, staying at home helps "flatten the curve" and reduces the workload on our health care system.

If you are unwell and need to see a doctor, call ahead to your GP or local hospital before attending. They can give you the best advice on what to do next.

Tests for COVID-19 will only be conducted on people who meet the clinical criteria for the illness. These criteria may change over time. Contact your doctor if you are unwell and think you may have the virus. They can give you the best advice on what to do next.

If you can't contact your regular doctor or local hospital, call Health Direct on 1800 022 222.

If you have breathing difficulties, call an ambulance.