New South Wales has recorded its first case of diphtheria of the throat in a century. 

A two-year-old child in the north of the state, who was not vaccinated against diphtheria, is in intensive care in a Queensland hospital, IndyNR and WIN News reported on Saturday. 

According to the North Coast Public Health Unit, the child has been given antibiotics, respiratory support and a diphtheria antitoxin, while the family and close contacts have received post-exposure prophylaxis. 

There is no risk to the wider community. 

This is the first time a case of diphtheria of the throat has been found in NSW in the last 100 years. Some more mild forms of the infection have been recorded in that period. 

"Diphtheria is very rare in Australia due to our longstanding childhood immunisation program. However, the disease has very serious outcomes and can be fatal," Dr Paul Douglas, director of North Coast Public Health, told IndyNR. 

He noted that the diphtheria vaccination is free and easy to access for every person from six weeks of age onwards. 

Dr Douglas asked families to be aware of their children's vaccination status and ensure they are up to date with all the required shots. 

According to NSW Health, diphtheria is a contagious bacterial infection, and can be life-threatening. It was a common cause of death for children until the 1940s. Now it primarily occurs in countries with low vaccination levels. 

It's usually spread from respiratory droplets when an infected person coughs or sneezes. Sometimes the bacteria can spread from close contact via discharges from an infected person's mouth, nose, throat or skin, but this method of transmission is rare. 

Without antibiotic treatment, people are usually infectious for up to four weeks from the onset of their symptoms. 

Symptoms depend on the site of infection, with the most severe form of the disease affecting the throat and tonsils. It begins with sore throat, a loss of appetite, and a mild fever. Within two or three days, a greyish-white membrane forms over the throat and tonsils that can make it hard to swallow and breathe. The neck may also swell. 

The toxin formed by diphtheria bacteria can also cause inflammation of heart muscle and the nerves, which can be fatal in 5-10 per cent of infected people. 

Sometimes it can also cause small skin sores that form large ulcers, commonly on the legs. 

The diphtheria vaccine is administered at two, four, six and 18 months of age, with further booster doses required at four years old and 15 years old. 

As of last year, more than 90 per cent of Australian children under six were fully immunised, according to data from the Australian Childhood Immunisation Register.