Department of Health

Health advisory

Advisory number:
Date issued:
27 Dec 2022
Issued by:
Dr Angie Bone, Deputy Chief Health Officer (Environment)
Issued to:
Health professionals and the public

What is the issue?

Significant flooding impacted Victoria during October and November 2022. Many health services, community services and care facilities were also impacted during that time.

Most of Victoria has now transitioned from response to recovery, with health services returning to normal operations.

As recovery efforts continue, the risk is now focused on mosquito borne diseases with the increased presence of mosquitoes in warmer weather and around stagnant water. Other risks include animal hazards (snakes and insects), and mould.

Who is at risk?

Anyone involved in clean-up and recovery efforts is potentially at risk of being bitten by mosquitoes, snakes and insects, and mould.

Other groups at greater risk include children, pregnant women, elderly people, tourists, homeless people, and those from minority populations.


For the public

Resources and information can be found on the Better Health ChannelExternal Link and the department’s floods page.

For health professionals

Key messages

  • Stagnant water and warmer weather may increase the risk of mosquito-borne diseases. After a flood, water and food-borne diseases, and uncommon conditions such as leptospirosis, carbon monoxide poisoning or illness relating to mould exposure, may also occur.
  • Consider flood-related diseases in patients who have spent time in flood affected areas.
  • Clinical presentations of these conditions may be non-specific. Clinicians should exercise a high index of suspicion for flood-related diseases to ensure correct diagnosis and management.
  • Clinicians should consider the many pathogens that can be responsible for flood-related gastrointestinal illness (e.g. hepatitis A virus, E. coli, Cryptosporidium) or wound infections (e.g. staphylococcal and streptococcal infections, Aeromonas and tetanus).
  • Food, medicine and other items containing flood water are considered contaminated and should be discarded.
  • In patients presenting with respiratory symptoms, consider exacerbations of pre-existing illness (e.g. asthma), COVID-19 infection and mould exposure.
  • Individuals impacted by floods may present with mental distress, suicidal ideation, substance use or involvement in interpersonal violence. Be alert to signs and triggers, and consider referral to appropriate support services and resourcesExternal Link . Psychological first aid resources are available at the websiteExternal Link .
  • Be alert to recognise the signs and triggers of domestic violence and direct patients to appropriate support servicesExternal Link .

Drinking water contamination

If flooding has affected the supply of safe reticulated drinking water, then the relevant water agency will issue either a “boil water”, “do not drink”, or a “do not use” advisory to customers depending on the nature of the issue. These advisories will detail alternative drinking water supply arrangements if required. Affected community members who have consumed potentially contaminated water will be advised to seek medical advice if they develop compatible symptoms.

Food and medicine safety

Food or medication that may be contaminated by flood waters should be discarded.

Dispose of food that has become spoilt due to power outages. Advice on managing contaminated food and water supplies is available on the Better Health channelExternal Link .

Medications that require refrigeration (e.g. insulin, eye drops, ear drops and reconstituted antibiotics) may need to be discarded if they have been subject to power outages. If the medications are essential to sustain health, they should continue to be used until a new supply is available.

Mosquito-borne risks

The risk of mosquito-borne diseases may increase after a flood around stagnant water and in warmer weather. In Victoria, these include the Ross River virus, Barmah Forest virus, Murray Valley encephalitis (MVE) virus and Japanese encephalitis (JE) virus. These conditions are notifiable in Victoria. JE and MVE viruses can cause severe illness and death in some people. JE vaccine is available free-of-charge for specific priority groups. View more information on JEV.

Japanese encephalitis (JE) is a rare but potentially serious infection of the brain caused by the JE virus (JEV). Infection is asymptomatic or associated with mild symptoms in most people, but it can cause severe disease including an acute encephalitis, causing death or chronic neurological sequelae.

Doctors should consider the possibility of mosquito-borne disease in patients presenting with a compatible illness, for example fever, rash, arthralgia or encephalitis, especially after travel to flood-affected areas.

Encourage individuals to avoid mosquito bites by covering up with long, loose-fitting clothing and using picaridin or DEET containing mosquito repellents. Stagnant water around homes and gardens should also be removed. Further guidance on this can be found on the Better Health channelExternal Link .


Leptospirosis, a disease caused by the Leptospira bacteria, is shed in the urine of infected mammals including livestock and rats. Transmission to humans can occur through cuts, abrasions or mucous membranes that are exposed to contaminated water or soil. Common initial symptoms include fever, headache, myalgia, vomiting and conjunctivitis. Severe disease can develop with jaundice, renal failure and haemorrhage. Symptoms usually develop 4 to 19 days following exposure.

Talk to the microbiology laboratory about testing for leptospirosis and request leptospirosis serology. Leptospirosis PCR can also be performed. If you suspect leptospirosis clinically, start antimicrobial therapy (usually empirical therapy with Doxycycline). Consult an infectious disease specialist and see Australian therapeutic guidelinesExternal Link . Leptospirosis is a notifiable condition in Victoria.

Although person-to-person transmission is rare, cases should be nursed with blood and body fluid precautions.


In Victoria, JE vaccine is currently available free-of-charge for specific priority groups. There is significant global demand for the JE vaccine. Victoria has a limited supply and therefore access is restricted to specific priority groups, targeted to those most at risk. Eligibility criteria will continue to be monitored.

For further information on these vaccines, eligibility criteria, their safety and administration see Japanese encephalitis virus vaccinesExternal Link .

Advise all people to take steps to keep themselves safe by following preventative measures to protect against mosquito-borne diseases.

Tetanus boosters may be administered to individuals who sustain open wounds, depending on their immunisation history. View more information on tetanus.


Wounds acquired whilst cleaning up after the flood can be heavily contaminated and require careful cleaning, irrigation, dressing and review. Waterproof dressings should be applied to prevent further floodwater contamination. Depending on immunisation status, tetanus toxoid should be administered.

Antibiotic prophylaxis is recommended for traumatic water-immersed wounds that are heavily contaminated or require surgical management, or in patients with underlying risk factors for developing severe infection. Consider the risk of Aeromonas and other possible water-associated skin infections, as well as staphylococcal and streptococcal infections. See Australian therapeutic guidelinesExternal Link .


Consider mould exposure in patients presenting with nasal congestion, sneezing, cough, respiratory infections and worsening asthma and allergic conditions. People with weakened immune systems, allergies, severe asthma or lung diseases are more susceptible to mould exposure. See After a flood: mould and your healthExternal Link .

Animal hazards

Patients may present following wild animal bites including from rodents, snakes or spiders. Initiate first aid and initial wound management. Ensure referral for surgical management and discussion with infectious disease specialists where appropriate. Ensure that tetanus immunisation is up to date. For bites involving bats or flying foxes, lyssavirus post exposure prophylaxis may be required.

Contact the Victorian Poisons Information Centre (VPIC) on 13 11 26 if there is a need for anti-venom. Further advice is available on the Health Translation websiteExternal Link .


Patients presenting with concerns around asbestos exposure should be advised to:

  • not disturb the material
  • take reasonably practicable steps to prevent others from disturbing the material.

The EPA also provides public health guidance on clean up and disposal. SeeDisposing asbestos waste after a floodExternal Link .

Carbon monoxide poisoning

Diagnosis of carbon monoxide (CO) poisoning can be challenging as symptoms are non-specific and can be mistaken for common illnesses such as flu-like illness or food poisoning. Symptoms may include headache, nausea and vomiting, skin flushing, muscle pain, weakness, shortness of breath, dizziness, coordination difficulties, confusion, chest pain and can lead to loss of consciousness and death.

When assessing patients, ask about sources of CO exposure including the use of portable generators, outdoor gas heaters (for example patio heaters) and BBQs indoors.

See Could it be carbon monoxide poisoning? for guidance for clinicians on CO poisoning.

If you suspect a patient is presenting with CO poisoning, seek advice from the Victorian Poisons Information CentreExternal Link on 13 11 26. Advise the Environmental Health Unit, Department of Health on 1300 761 874 of all elevated results.

Reviewed 28 December 2022

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