Americans are getting greater access to coronavirus test kits that aim to detect the virus easily and quickly from the comfort of one's home.

There are two types of at-home tests on the market. One is a saliva test, the other a swab test.

The saliva test is an alternative to the uncomfortable nasal swabs now widely used. A user dribbles saliva into a test tube, seals it and sends it to a lab. Doctors examine the secretions to determine if the person has been infected with the virus.

The swab test requires a person to swab the inside of their nose or cheek, producing a sample for analysis.

The saliva tests are just as effective as ones administered by a doctor, according to the Food and Drug Administration (FDA). Studies also have found saliva tests pose less risk to healthcare workers compared with nasal swabs, the FDA said.

A report by Yale University called "Saliva" said the test is more sensitive than naval swabbing for detecting the virus that causes COVID-19.

"When we compared SARS-CoV-2 detection from patient-matched nasopharyngeal and saliva samples, we found that saliva yielded greater detection sensitivity and consistency throughout the course of infection," the report said.

In November, Minnesota became the first state to roll out at-home tests. At least 261,000 kits made by Infinity BiologiX have been distributed, according to The New York Times.

In Orange County, California, 500,000 saliva test kits will be given to 3.4 million residents by the end of December. The tests will be sent to people in Anaheim and Santa Ana, two populous California cities with large immigrant communities.

Counties in New Jersey also are offering the saliva tests. But an effort in Burlington County encountered problems. At least 2,400 kits were sent to residents, but the program was halted after only 900 were mailed back, and the rest were unused.

Burlington County Health Director Dr Herb Conaway said in a statement: "The program was designed for homebound residents and those who were unable to travel to our fixed test site or mobile sites. Unfortunately, numerous people have requested the test kits but failed to return them with collected samples for testing, essentially keeping the kits until they decide they need them."

Schools, colleges and sports leagues also are using the saliva tests. The Greenwich Academy, a private prep school for girls in Connecticut, and the Washington University Medical School in St. Louis are among those using the test.

Several companies now sell the at-home saliva test. They include Vault, Vitagene, Hims and Hers and Phosphorus. The tests range in price from $129 to $150.

At-home tests that use mouth swabs are sold by Pixel by LabCorp, LetsGet Checked and Everlywell. They are priced from $119 to $150.

A person who does or doesn't have symptoms can order a test. If it comes from a state-run program, then the kits are paid for by the state offering them, or people can use their health insurance to purchase them. They usually arrive in 24 hours.

A healthcare worker can supervise how to use the kit properly on a Zoom conference call. Test results are usually ready in one to two days.

Dr Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, has stressed since the start of the pandemic that widespread testing is crucial to stop the spread of the virus.

It is hoped that the increased use of at-home tests will help as there is still a fairly long wait to get a coronavirus test from a doctor or pharmacy. Long lines have been seen outside doctors' offices in New York City, Atlanta and other cities.

Medical testing companies first developed at-home saliva testing kits at the height of the pandemic in March.

In May, the first diagnostic saliva test kit to get FDA approval was developed by RUCDR Infinite Biologics, a unit of Rutgers' Human Genetics Institute of New Jersey, and Spectrum Solutions and Accurate Diagnostic Labs for use at Rutgers University. It can be bought online for $150.