Doctors and public health experts have warned that the United States could face a deadly "twindemic" this fall and winter if many diagnoses of flu and COVID-19 arise during the same time frame.

The warning of a possible "twindemic", with a deluge of people being infected and hospitalized with flu or COVID-19, comes after the Centers for Disease Control and Prevention found that the number of influenza cases is already higher than normal at this time of year.

William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee, told China Daily: "There is a substantial risk of a twindemic this fall.

"We anticipate that as the weather gets colder, and people go indoors, once again, there will be opportunities for this virus (COVID-19) to be transmitted.

"Influenza has started up about a month early in several places in the country, particularly in the southeast, where we have already seen many people hospitalized with laboratory diagnosed influenza."

The flu season typically occurs in December and peaks in February. But this October, cases of influenza are notably higher in Georgia, New York, South Carolina, Tennessee, Texas and Washington, DC.

One of the most notable flu strains of concern is the H3N2. It tends to be dangerous for those older than 65, with a weak immune system and the very young.

There are fears that a widespread cases of both viruses could strain the US healthcare system. The CDC said that from 2010 to 2020 there were between 140,000 and 710,000 hospitalizations from flu per year and 12,000 to 52,000 deaths annually.

"We anticipate that this will be a vigorous winter respiratory virus season," Schaffner said. "And we could have concurrent coincidental flu and COVID increases, which once again, could strain our healthcare system substantially."

Cases of flu diminished significantly amid the coronavirus pandemic because of the precautions people were taking against catching COVID-19, including wearing masks, cleaning their hands frequently and social distancing.

As more adults get back to work and mingle in public, several public health experts advise that it will be important for everyone to be vaccinated against the flu and COVID-19 to aid their fight against infection.

Doctors and public health experts recommend anyone who is eligible to receive a flu shot and a COVID-19 vaccine.

Flu and COVID-19 vaccines can be administered together and the over-65s and pregnant women should get them, as both groups are susceptible to catching the viruses.

However, amid ongoing fears over vaccinations, the rate of people getting the flu vaccine this year appears to be lower than in previous years, according to the CDC's Weekly National Flu Vaccination Dashboard.

An estimated 7.5 million flu vaccinations were administered in US pharmacies in the week ending Sept 24, compared with an estimated 7.9 million at the same time last September.

An estimated 4.2 million flu vaccinations were administered in US physicians' medical offices in the week ending Sept 24, compared with an estimated 5.7 million at the same time in September 2021. As of Oct 1, 105.8 million doses of flu vaccine had been distributed in the US.

The flu vaccine is produced by private manufacturers, so supply will depend on production. The CDC said that "vaccine manufacturers have projected that they will supply the US with as many as 173.5 million to 183.5 million doses of influenza vaccines for the 2022 to 2023 season".

Schaffner added that the best way to stay protected against both flu and COVID-19 is by getting inoculated.