The State of Florida has confirmed four cases of Zika infection in a small Miami neighbourhood, and announced over the weekend that they were likely caused by mosquito bites.

This makes Florida the first state in the continental United States to experience a local transmission of the virus, and officials are urging locals to get tested. 

"The bottom line is that Zika is now here," Tom Frieden, director of the Centres for Disease Control and Prevention (CDC), announced in a press briefing.

"Florida has become the first state in our country to have a local transmission of the Zika virus," the governor of Florida, Rick Scott, said at a separate press conference in Orlando.

So how did this all happen? Last week, officials confirmed that four unexplained Zika cases had cropped up in Florida's Miami-Dade and Broward counties.

The three men and one woman infected with the virus had not travelled to Zika-affected countries and brought back an infection, nor had they contracted the virus sexually, leaving experts to state that by far the most likely explanation was that they'd been infected by local Aedes aegypti mosquitoes.

To be clear, all we have to go on right now is circumstantial evidence, and so far, no local mosquitos have been found to be carrying Zika. But as Frieden told Rita Rubin from Forbes, this isn't exactly a surprise, as finding the individual culprits is like "finding a needle in a haystack".

The CDC is now advising that everyone in the area - especially pregnant women or women planning to get pregnant - to avoid mosquito bites and get tested. Though the virus only produces fairly mild symptoms, such as a fever or a rash, in most adults, in pregnant women, it can cause very serious defects in children born with microcephaly.

"All the evidence we have seen indicates that this is mosquito-borne transmission that occurred several weeks ago in several blocks in Miami," Frieden said in a CDC press release.

"We continue to recommend that everyone in areas where Aedes aegypti mosquitoes are present - and especially pregnant women - take steps to avoid mosquito bites. We will continue to support Florida's efforts to investigate and respond to Zika and will reassess the situation and our recommendations on a daily basis."

The good news is all four cases appear to have been transmitted in an area of just 1 square mile (2.6 square kilometres) just north of downtown Miami.

As George Dvorsky reports for Gizmodo, the exact location is within Northwest 5th Avenue to the west, US 1 to the east, Northwest/Northeast 38th Street to the north and Northwest/Northeast 20th Street to the south. 

You can see the affected area in this map.

The other good news is that the CDC says that even if they do manage to confirm that local mosquitos are transmitting the virus, it's unlikely this will turn into a full-blown epidemic, the likes of which have been seen in several areas of Latin American and the Caribbean.

"Our environment isn't conducive to those mosquitoes," Frieden said in the press briefing, "partly because people use screens and air-conditioning. For whatever the reason, we don't generally see clusters.

Frieden added that Aedes aegypti mosquitoes can only travel up to 150 metres (about 500 feet) in their lifetime, making it very difficult for them to make it out of the affected area.

"We do not believe there will be ongoing transmission," Florida Surgeon General, Celeste Philip, told the press in Orlando. 

If you're in the affected area, expect to see a temporary ban on blood donations for some time, and you just might have health officials knocking on your door with free mozzie repellents. Stay safe, everyone.