The Townsville Hospital and Health Service says it may declare an outbreak of dengue fever in the city with two confirmed cases and another suspected.

Key points: Cases of the mosquito-borne illness dengue are not unusual in the region, but these are the first cases acquired from local insects since 2016

Cases of the mosquito-borne illness dengue are not unusual in the region, but these are the first cases acquired from local insects since 2016 Townsville's Northern Beaches is suspected to be the link between the infections, an area excluded from a successful Wolbachia program

Townsville's Northern Beaches is suspected to be the link between the infections, an area excluded from a successful Wolbachia program The infections place increased pressure on health services dealing with a jump overnight of local COVID-19 cases from 6 to 11

Confirmed cases include a Stuart woman and a Condon man, while a case is being investigated in the suburb of Northern Beaches where health officials suspect the potential outbreak has started.

The viral illness, transferred when a person is bitten by an infected mosquito, often starts with fever, headache, muscle and joint pain, extreme tiredness, or a rash.

In some cases a patient may experience symptoms like a loss of appetite, vomiting, diarrhoea, abdominal pain, or a metallic taste in the mouth.

Cases of the mosquito-borne illness are not unusual in the region, but the health service said these are the first cases acquired from local insects since 2016.

In a statement, Townsville Public Health Unit physician Dr Julie Mudd said the only cases seen in Townsville for years had been contracted from overseas.

Townsville Public Health Unit physician Dr Julie Mudd says Townsville may be facing a dengue outbreak. ( ABC News: Nathalie Fernbach )

Dr Mudd said with no links to overseas travel, the recent cases are concerning.

"This cluster is significant because neither case has travelled, which means the virus has become established in at least some pockets of our local Aedes aegypti mosquito population," Dr Mudd said.

She said dengue is spread when an infected dengue mosquito bites someone with the illness and, several days later, can give the virus into another person it bites.

Program targeted disease-carrying mosquitoes

A spokesman for the Townsville Hospital and Health Service said the confirmed cases are believed to be linked to a suspected case in the Northern Beaches.

The area was excluded from Townsville City Council's successful Wolbachia program.

Program staff release the first Wolbachia bacteria-infected mosquitoes in a Townsville backyard in 2014. ( ABC News: Allyson Horn )

The program began in 2014 and saw specially-modified mosquitoes, which cannot transmit the virus, released in the Townsville community.

Now the Townsville Hospital and Health Service is having to tackle the problem insects again.

"The dengue action response team is conducting control activities in the suburbs where the local cases were confirmed including removing breeding sites, placing traps, interior and exterior spraying, and health promotion activities," a spokesman said.

Local general practitioner Dr Michael Clements said Townsville GPs are on the lookout for patients with symptoms including fevers, aches, and pains.

"To the average punter that feels sick and crook they're not able to tell the difference," Dr Clements said.

Locals warned not to be complacent

The infections place increased pressure on local health services and practitioners who overnight saw the number of Townsville-based COVID-19 cases jump from 6 to 11.

Dr Clements said there also had been a resurgence of other mosquito-borne illnesses such as Ross River virus.

Townsville residents are being encouraged to use mosquito coils among other measures to deter mosquitoes. ( ABC News )

"There's certainly been a few reports of that around so GPs are being kept very busy at the moment," she said.

The Townsville Public Health Unit is urging residents to tip out any containers of water, spray their homes with insecticide, and wear mosquito repellent.

"These mosquitoes breed in small quantities of water found in tyres, buckets, toys, or pot plant bases," Dr Julie Mudd said.

"Get out the surface or cockroach inspect spray and spray in dark or hiding places, in and around your homes.

"If you don't have long-acting surface spray or electric zappers or coils, the next time you do a shop pick some up."