Infectious and communicable diseases is an Australia's health topic

Infectious diseases are caused by infectious agents (bacteria, viruses, prions, parasites and fungi and their toxic products). Many infectious diseases are also communicable diseases, meaning they can be passed from one person or animal to another. Transmission can occur directly (through contact with blood and bodily fluids) or indirectly (through contaminated food, water, air or surfaces) or by means of vectors (such as mosquitoes). Examples of these communicable diseases include measles (transmitted by airborne droplets and direct contact with respiratory secretions and contaminated surfaces and objects), malaria (transmitted by mosquitoes), and chlamydia (direct transmission through sexual contact). 

Most people will experience an infectious disease at some point, such as a common cold or a stomach bug. While many infections are mild and short-lived, others can cause severe illness, outbreaks, and even deaths. Some infectious diseases have also developed resistance to antimicrobial agents, increasing the risk of more lengthy and complex treatment and poor outcomes (Australian CDC 2026a).

Because mild cases often go unreported, it is difficult to measure the true incidence of many infectious diseases. To support public health action for prevention and control of their spread, certain infectious diseases are notifiable conditions. When a diagnosis is made of one of these diseases, a report is made to health authorities.

What are notifiable diseases?

Notifiable diseases are a subset of infectious diseases that present a risk to public health in Australia. Legislation requires that each detected case is reported to state and territory health departments, who then report case data to the Australian Centre for Disease Control. Notifiable diseases include certain bloodborne diseases, gastrointestinal infections, sexually transmissible infections, vaccine-preventable diseases, respiratory diseases, vector-borne diseases, zoonotic diseases, listed human diseases, and other notifiable diseases (see National notifiable disease list).

Notification enables monitoring of trends in the number and characteristics of cases over time. Outbreaks can then be detected in a timely way so that interventions can be implemented to prevent or reduce transmission. Data presented on this page from the NNDSS were extracted on 5 January 2026. Due to the dynamic nature of the NNDSS, surveillance data may vary from data reported in other national reports, including NNDSS annual reports, or other state and territory reports. Human immunodeficiency virus (HIV) and Creutzfeldt-Jakob disease (CJD) notifications are not available through NNDSS. For more information on HIV notifications, see UNSW Kirby Institute HIV.

This page highlights the impact of infectious diseases in Australia, both notifiable and non-notifiable.

Infectious diseases over time

Throughout the 1900s, improved sanitation and new prevention and treatment options drastically reduced the burden of infectious diseases. Immunisation and vaccination are key preventive measures against infectious and communicable diseases and have been highly successful at reducing infections and deaths from transmissible diseases. Australia’s high vaccination coverage, along with well-developed disease surveillance and response systems, led to Australia being declared polio-free in 2000, and achieving measles elimination in 2014 and rubella elimination in 2017. While Australia has maintained its measles elimination status, the rise in measles cases globally has resulted in imported measles cases, with 181 notifications for measles recorded nationwide in 2025, the highest number since 2019 (Australian CDC 2026b).

The emergence of COVID-19 in late 2019 marked a major global health challenge. Declared a pandemic in March 2020, COVID-19 has caused more than 778 million reported cases and over 7 million deaths worldwide (WHO 2025). The true numbers are likely to be much higher as many cases and deaths from COVID-19 may go undetected and unreported (COVID-19 Excess Mortality Collaborators 2022; Lau et al. 2021). In Australia, over 12 million confirmed or probable cases were reported as at 5 January 2026 (Australian CDC 2026b). Since the start of the pandemic, a total of 21,447 people have died due to COVID-19 (registered by 31 March 2025) (ABS 2024, ABS 2025).

Post COVID-19 condition, or long COVID, is a health issue defined by persistent or new symptoms lasting at least three months after initial infection (Ely, Brown and Fineberg 2024). It is a multisystem disease with many subtypes ranging from symptoms such as brain fog and fatigue, which is most common in females and younger adults, to cardiovascular and metabolic sequelae observed more commonly in older adults and those with comorbidities (Al-Aly and Topol 2024). Data on the prevalence of post COVID-19 condition in Australia are largely obtained from surveys, with estimates ranging from 5% to 10% of people who have had COVID-19 reporting symptoms lasting 3 months or more (Biddle and Korda 2022; Liu et al. 2021; Sax Institute 2022; Staples et al. 2023). For more information, see COVID-19.

In 2024, COVID-19 caused a notable health burden in Australia, accounting for 43,950 DALY (1.24 DALY per 1,000 population). This represented 0.8% of the total disease burden and nearly 29% of the burden from all infectious diseases. The burden of COVID-19 was predominantly fatal and was higher in males (AIHW 2024). For more information, see Burden of disease.

Looking ahead, significant demographic, technological, and environmental changes in the 21st century present future threats to the spread of infectious diseases. Increased urbanisation and population density creates opportunities for more persistent infectious disease outbreaks. Globalisation increases the risk of importing and exporting pathogens. Climate change is expanding the seasonal and geographic dynamics of many infectious diseases, and is expected to be the driving cause of increasing infectious disease rates in new populations (Baker et al. 2022).

How common are infectious diseases?

We do not know the true incidence of all infectious diseases in Australia, as only a subset of infectious diseases are notifiable. However, data from the National Hospital Morbidity Database and the National Mortality Database give an indication of the impact of serious conditions due to infectious diseases that required hospitalisation and/or caused deaths. 

Notifiable diseases

Over 1.1 million cases of notifiable diseases were reported to the NNDSS in 2025, with influenza and COVID-19 together accounting for more than half of all notifications that year.

The diseases with the highest number of notifications in 2025 included:

  • Influenza (laboratory confirmed) – more than 499,300 notifications (42% of the total notifications)
  • COVID-19 – more than 184,600 notifications (15% of the total notifications)
  • Respiratory syncytial virus (RSV) – almost 177,100 notifications (15% of the total notifications)
  • Chlamydia (a sexually transmissible infection) – more than 93,000 notifications (8% of the total notifications)
  • Gonorrhoea (a sexually transmissible infection) – more than 42,000 notifications (4% of the total notifications)
  • Campylobacter (a gastrointestinal infection) – more than 39,000 notifications (3% of the total notifications)
  • Pertussis (whooping cough) – more than 25,000 notifications (2% of the total notifications).

Figure 1: Number of notifiable infectious diseases, Australia, 2009 to 2025

This figure presents a line graph showing the number of notifications for various notifiable diseases between 2009 and 2025. The reader can select all notifiable diseases or specific sub-types and individual diseases. The data show that the most commonly notified bloodborne disease was hepatitis C (unspecified), the most common gastrointestinal infection was campylobacteriosis, the most common STI was chlamydia, the most common vector-borne disease was Ross River virus, the most common vaccine-preventable disease was influenza, the most common zoonotic disease was Q fever and the most common other bacterial disease was tuberculosis. The number of notifications for many diseases decreased during 2020 to 2023.

This figure presents a line graph showing the number of notifications for various notifiable diseases between 2009 and 2025. The reader can select all notifiable diseases or specific sub-types and individual diseases. The data show that the most commonly notified bloodborne disease was hepatitis C (unspecified), the most common gastrointestinal infection was campylobacteriosis, the most common STI was chlamydia, the most common vector-borne disease was Ross River virus, the most common vaccine-preventable disease was influenza, the most common zoonotic disease was Q fever and the most common other bacterial disease was tuberculosis. The number of notifications for many diseases decreased during 2020 to 2023.

Vaccine-preventable diseases

One key group among notifiable diseases is vaccine-preventable diseases (VPDs). Many VPDs such as rubella, diphtheria and tetanus are now rare in Australia, because of Australia’s high childhood immunisation rates. However, some diseases, including pertussis (whooping cough) and measles, can still cause outbreaks when people with low or no immunity become infected.

COVID-19 dominated Australia’s disease notifications in 2022, making up 95% of all reported notifiable disease cases that year. Since then, COVID-19 case numbers have fallen, partly because fewer cases are being detected due to changes in testing and reporting requirements. Hospitalisations and deaths linked to COVID-19 also peaked in 2022 (AIHW 2025).

Notifications for several VPDs including influenza and pertussis dropped sharply during the COVID-19 pandemic in 2020 and 2021. This is likely due to public health measures, such as physical distancing, international and local travel restrictions, lockdowns, mask-wearing and handwashing, which would have also affected the spread of other infectious diseases, particularly respiratory viruses (Sullivan et al. 2020). People may also have been less likely to seek medical care for minor illnesses, leading to under-diagnosis and under-reporting. 

After public health restrictions eased in 2022 and 2023, notifications for these VPDs increased again, notably for influenza and pertussis. Similar post‑pandemic resurgences have been observed globally, reflecting the re‑establishment of respiratory virus transmission, including influenza, respiratory syncytial virus and pertussis (Feinmann 2024, Gorringe et al. 2025). In 2025, Australia recorded its highest number of influenza cases since 2010, with nearly 500,000 notifications. Influenza-related hospitalisations and deaths, which had fallen in 2020 and 2021, also increased after 2022 (AIHW 2025). Pertussis notifications followed a similar pattern: after a sharp decline during the pandemic, cases surged post pandemic, peaking at over 57,000 notifications in 2024, the highest since 1991 (Australian CDC 2026b).

Respiratory syncytial virus (RSV) did not become notifiable in all states and territories until 1 September 2022. Comprehensive national RSV notification data show an increase in RSV notification rates in Australia from 2023 to 2024, particularly among younger children aged 0 to 4 years (AIHW 2025). For more information, see Vaccine-preventable diseases in Australia, Fact sheets.

In 2025, 181 measles cases were notified, up from 57 cases in 2024 (Australian CDC 2026b). This increase, along with rising cases of influenza, RSV and pertussis in Australia, highlights the important role of vaccination in protecting communities. While any measles case poses a risk to infants too young to be vaccinated, and unvaccinated or partially vaccinated children, the majority of measles cases in the past decade have occurred in adults aged 20–49 years. This underscores the importance of catch‑up and booster vaccination, in addition to routine childhood immunisation, to prevent importation and onward spread.

Vaccination prevents severe illness and death, reduces transmission, and helps protect those most vulnerable, including infants too young to be vaccinated, older adults and people with weakened immune systems. Recent declines in childhood and adolescent vaccination rates are concerning and highlight the need for ongoing public health efforts to support immunisation and address potential barriers to access. For more information, see Immunisation and vaccination.

Sexually transmissible infections and blood borne viruses

Significant progress has been made in the prevention and management of blood borne viruses (BBVs) and sexually transmissible infections (STIs) in Australia. However, infections such as hepatitis B, hepatitis C, HIV, chlamydia, gonorrhoea and syphilis remain significant public health issues.

In 2025, hepatitis C was the most commonly notified BBV in Australia. There were over 800 notifications of newly acquired hepatitis C (cases with evidence of hepatitis C acquisition within two years before diagnosis) and over 6,200 cases unspecified hepatitis C notifications (cases that do not meet any of the criteria for a newly acquired infection and are either more than 24 months in duration or of unknown duration).

Between 2016 and 2025, hepatitis C notification rates declined by 46%, from 46.6 to 25.4 per 100,000 population. This sustained decline over the past decade has been largely attributed to the introduction of government-funded hepatitis C antiviral treatments, specifically interferon free direct acting antiviral (DAA) therapies, on the Pharmaceutical Benefits Scheme (PBS) in March 2016. Following their introduction, there was a rapid uptake of treatment and cure among people living with hepatitis C (King et al. 2025).

The HIV notification rate has also generally declined over the past decade. In 2024, there were 757 new HIV diagnoses, representing a 27% reduction since 2015. This decline has been attributed to targeted prevention measures, including the rollout of pre‑exposure prophylaxis (PrEP) and the promotion of the U=U (‘Undetectable equals Untransmittable’) principle, which means that when a person living with HIV is taking treatment and has an undetectable viral load, they cannot sexually transmit HIV (King et al. 2025).

Notification rates for chlamydia and gonorrhoea increased between 2015 and 2019, declined from 2019 to 2021 due to factors associated with the COVID-19 pandemic, and then increased again from 2021 to 2024, with similar trends among males and females. Over the same period, the infectious syphilis notification rate increased from 11.9 to 22.1 per 100,000 population, with a steeper increase among females than males. New syphilis cases in Australia are diagnosed mainly in men who have sex with men residing in urban areas, or young First Nations people in Remote or Very remote regions, although more recently increasing numbers of cases have occurred among non-Indigenous women of reproductive age (15–44 years) in urban areas. Between 2020 and 2025, 91 cases of congenital syphilis (when the infection passes from mother to baby during pregnancy or at birth) were reported (Australian CDC 2026b).

STI notification rates among Aboriginal and Torres Strait Islander (First Nations) people remain disproportionately high compared with non-Indigenous people. In 2024, infectious syphilis notifications rates were more than five times higher among First Nations people, gonorrhoea rates were four times higher, and chlamydia rates were twice as high. Limited access to culturally appropriate health services for testing and treatment, combined with the impact of social determinants (such as geographical and financial barriers to accessing care, lower levels of educational attainment, lower income, and exposure to alcohol and drugs, which are associated with sexual behaviours that increase risk of STIs) contribute to this disparity (King et al. 2025; Wand et al. 2016; Ward et al. 2020). In 2022, a pilot collection of information about testing for STI among First Nations people aged 15–34 was introduced as a part of the national Key Performance Indicators (nKPIs) for Indigenous-specific primary health care organisations. The 2024 results show that nearly 30% of First Nations regular clients received a test for one or more STIs that year (AIHW 2026). For more information on the nKPI collection, see Aboriginal and Torres Strait Islander specific primary health care: results from the OSR and nKPI collections.

Varying prevention and control measures are used by public health authorities depending on the type of infection and target population. Monitoring of the priority populations most commonly affected by STI and BBV allows targeted prevention programs to be designed. The ongoing response to STI and BBV in Australia is being coordinated by the Australian Centre for Disease Control through the 5 National Blood Borne Viruses and Sexually Transmissible Infections Strategies including:

  • Fourth National Hepatitis B Strategy 2025–2030
  • Sixth National Hepatitis C Strategy 2025–2030 
  • Fifth National STI Strategy 2026–2030 (in draft)
  • Sixth National Aboriginal and Torres Strait Islander BBV and STI Strategy 2024–2030
  • Ninth National HIV strategy 2024–2030 (Australian CDC 2025).

The Strategies aim to eliminate blood borne viruses and STI as public health issues by 2030. In addition, the HIV Taskforce was established in 2023 to review Australia’s efforts to end the HIV epidemic, with the goal of achieving virtual elimination of HIV transmission in Australia by 2030 (Australian CDC 2023).

Non-notifiable diseases

Non-notifiable infectious diseases are not routinely monitored, though their impact can be tracked through assessing presentations to hospital, or through mortality data. These data sources capture the small proportion of people who have severe illness, causing hospitalisation or resulting in death. Information on hospitalisations and deaths from non-notifiable infectious diseases is presented in the following sections.

Classifying non-notifiable infectious diseases

Non-notifiable infectious diseases are broadly categorised based on the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM) codes for hospitalisations and International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) for deaths. The categories used here include gastrointestinal infections (other than those which are notifiable), upper respiratory tract infections, lower respiratory tract infections (excluding COVID-19, influenza and RSV), other meningitis and encephalitis, trachoma, abscess causing pneumonia, otitis media, unspecified viral hepatitis, and other infections. Abscess causing pneumonia is not listed as a separate category in mortality coding. 

The impact of infectious diseases

Hospitalisations

In 2024, there were more than 557,000 hospitalisations due to infectious diseases. Hospitalisation rates for infectious diseases increased steadily between 2007 and 2019, driven mainly by increases in non-notifiable diseases. After falling in 2020 and 2021, the hospitalisation rate for infectious diseases surged to 26 per 1,000 people in 2022 – the highest since 2000 – largely due to COVID-19 related hospitalisations. Rates then declined to 20 per 1,000 people in both 2023 and 2024.

Before 2022, notifiable diseases accounted for about one in ten infectious disease hospitalisations. In 2022, they made up over half of all infectious disease hospitalisations, with the majority being COVID-19 related hospitalisations. By 2024, notifiable diseases contributed to roughly one-third of hospitalisations, with the rest from non-notifiable diseases.

Figure 2: Hospitalisations/deaths due to notifiable and non-notifiable infectious diseases, Australia, 2000 to 2024

This figure presents a line graph with 3 lines showing notifiable diseases, non-notifiable diseases, and total infectious diseases. The reader can select either hospitalisations or deaths, and numbers or crude rates. The data show that hospitalisations from non-notifiable diseases were considerably more common than from notifiable diseases, but that hospitalisations decreased substantially in 2020 and 2021. Deaths from non-notifiable diseases were considerably more common than from notifiable diseases in the period between 2000 and 2021. However, in 2022, deaths from notifiable diseases were twice as high as deaths from non-notifiable diseases. The number of deaths and crude death rate increased substantially in 2022, due to a sharp increase in deaths attributed to notifiable diseases. 

This figure presents a line graph with 3 lines showing notifiable diseases, non-notifiable diseases, and total infectious diseases. The reader can select either hospitalisations or deaths, and numbers or crude rates. The data show that hospitalisations from non-notifiable diseases were considerably more common than from notifiable diseases, but that hospitalisations decreased substantially in 2020 and 2021. Deaths from non-notifiable diseases were considerably more common than from notifiable diseases in the period between 2000 and 2021. However, in 2022, deaths from notifiable diseases were twice as high as deaths from non-notifiable diseases. The number of deaths and crude death rate increased substantially in 2022, due to a sharp increase in deaths attributed to notifiable diseases. 

Among non-notifiable diseases, lower respiratory tract infections (such as pneumonia and bronchitis, excluding influenza, RSV, and COVID-19) were the most common cause of hospitalisation. Hospitalisation rates generally increased from 4.6 per 1,000 people in 2000 to 5.9 per 1,000 people in 2019, dropped to 3.6 per 1,000 people in 2020, then rose again to 5.4 per 1,000 people in 2024 (Figure 3).

Gastrointestinal infections (excluding notifiable infections such as campylobacteriosis, cryptosporidiosis, rotavirus, and salmonellosis) were the second most common cause of hospitalisation among non-notifiable diseases in most years.

Figure 3: Hospitalisations/deaths due to non-notifiable infectious diseases, by disease type, Australia, 2001 to 2024

This figure presents a line graph with lines for each of the non-notifiable disease sub-types. The reader can select either hospitalisations or deaths, and numbers or crude rates. The data show that lower respiratory infections were the most common cause of hospitalisation for the period between 2001 and 2021, and of deaths for the period between 2001 and 2022.

This figure presents a line graph with lines for each of the non-notifiable disease sub-types. The reader can select either hospitalisations or deaths, and numbers or crude rates. The data show that lower respiratory infections were the most common cause of hospitalisation for the period between 2001 and 2021, and of deaths for the period between 2001 and 2022.

For notifiable diseases, hospitalisation rates ranged between 1.1 and 2.2 per 1,000 people over the period 2000 to 2019, rising sharply to 14.2 per 1,000 in 2022 before dropping to 6.3 per 1,000 in 2024 (Figure 2). Influenza was a leading cause of notifiable disease hospitalisations in most years, peaking in 2019 (over 35,600 hospitalisations, or 1.4 per 1,000 people), followed by 2017 (over 31,000 hospitalisations, or 1.3 per 1,000 population) and 2024 (over 27,900, or 1.0 per 1,000 population). Influenza hospitalisation rates are highest among children under 5 and adults 65 and over. For more information, see Influenza in Australia (2025) fact sheet [PDF 300kB].

Hospitalisations where COVID-19 infection was recorded increased sharply from about 2,600 (0.1 per 1,000 population) in 2020 to over 320,000 (12.3 per 1,000 population) in 2022, before declining to about 103,200 (3.8 per 1,000 population) in 2024. COVID-19 hospitalisation rates are the highest among adults 65 and over. For more information, see COVID–19 in Australia (2025) fact sheet [PDF 250kB].

For more information on hospitalisation in Australia, see Hospitals.

Deaths

Between 2000 and 2021, deaths attributed to infectious diseases were generally stable, ranging from a low of 3,809 deaths (18 per 100,000 people) in 2008 to a high of 7,397 deaths (30 per 100,000 people) in 2017. Over this period, infectious diseases accounted for around 4% of all deaths in Australia. Non‑notifiable diseases, particularly lower respiratory tract infections, contributed the majority of infectious disease deaths in most years. 

In 2022, deaths due to infectious diseases increased sharply to 15,802, or 61 per 100,000 people, contributing to more than 8% of total deaths in Australia. Infectious disease deaths declined in subsequent years, to 11,376 (43 per 100,000) in 2023 and 11,180 (41 per 100,000) in 2024. Despite this decline, infectious disease mortality remained well above the levels observed between 2000 and 2021. The higher number of infectious disease deaths since 2022 has largely been driven by notifiable diseases, which accounted for 67% of all infectious disease deaths in 2022 and around half in both 2023 and 2024.

COVID-19 was the most common cause of notifiable disease deaths since 2020. At its peak in 2022, 9,859 deaths (38 per 100,000) were attributed to COVID-19, accounting for 93% of all notifiable disease deaths and more than 60% of all infectious disease deaths. Deaths due to COVID-19 have since declined, with 5,006 deaths (18.8 per 100,000) registered in 2023, and 4,025 deaths (14.8 per 100,000) in 2024. COVID-19 death rates are highest among people aged 80 and over. For more information on deaths from COVID-19, see Australia’s health 2022: data insights article The impact of a new disease: COVID-19 from 2020, 2021 and into 2022 Australia’s health 2022: data insights and COVID–19 in Australia (2025) fact sheet [PDF 250kB].

Influenza was the most common cause of notifiable disease deaths between 2000 and 2019. The highest number of influenza deaths was recorded in 2017, with 1,266 deaths (5.1 per 100,000), followed by 2019 with 1,076 deaths (4.2 per 100,000). In more recent years, influenza was recorded as the underlying cause of 437 deaths in 2023 and 825 deaths in 2024. Most influenza deaths occurred in people aged 65 and over (AIHW 2025). Deaths due to RSV increased in recent years, from 55 deaths in 2022 to 131 in 2024.

For more information on deaths in Australia, see Life expectancy and deaths. 

Where do I go for more information?

For more information on infectious diseases, see: