The Navy reports that the number of sailors aboard the USS Kidd confirmed to be infected with the novel coronavirus has nearly doubled, rising from 18 to 33.

The destroyer with its crew of 350 are off the Pacific coast of South America. Its current mission is related to US counter-drug activities.

In a statement issued today, the Navy said an embarked medical team continues testing of the Kidd's crew.

The guided-missile destroyer USS Kidd in the Pacific Ocean. (AP)

Two sailors have been medically evacuated to the United States. Meanwhile, officials say those aboard the Kidd are wearing N95 masks and other personal protective equipment.

The Navy says the amphibious assault ship USS Makin Island is en route to rendezvous with Kidd in case medical support is required at sea. Officials say the Makin Island has a fleet surgical team, intensive care capacity and ventilators as well as additional testing capability.

The Kidd is the second Navy ship at sea to report an outbreak of the coronavirus.

Officials say the aircraft carrier USS Theodore Roosevelt has reported more than 850 cases of infection among its nearly 5,000 crew members. Most of its crew has been moved ashore to quarantine on Guam.

The Navy reports that the number of sailors aboard the USS Kidd confirmed to be infected with the novel coronavirus has nearly doubled, rising from 18 to 33. (AP)

"And we think that this is a really important point to emphasise because we're concerned that if this could be present, that these antibodies could be misinterpreted, people could put themselves at unnecessary risk," Dr Hayden said.

Coronavirus: what you need to know

How is coronavirus transmitted?

The human coronavirus is only spread from someone infected with COVID-19 to another . This occurs through close contact with an infected person through contaminated droplets spread by coughing or sneezing, or by contact with contaminated hands or surfaces.

How can I protect myself and my family?

World Health Organisation and NSW Health both recommend basic hygiene practices as the best way to protect yourself from coronavirus.

Good hygiene includes:

Clean your hands thoroughly for at least 20 seconds with soap and water, or an alcohol-based hand sanitiser;

Cover your nose and mouth when coughing and sneezing with tissue or your elbow;

Avoid close contact with anyone with cold or flu-like symptoms;

Apply safe food practices; and

Stay home if you are sick.

Tops tips for minimizing coronavirus transmission. (9News)