It looks like the US Centers for Disease Control and Prevention (CDC) can’t make up their mind on masks for monkeypox.

In a muddled U-turn, the CDC briefly advised travelers to wear masks to reduce the risk of catching monkeypox before deleting the recommendation to avoid "confusion".

Last week, the CDC updated its monkeypox travel advice to say: “Wear a mask. Wearing a mask can help protect you from many diseases, including monkeypox.”

Now, amid criticism on social media, that recommendation is gone. According to Reuters, a CDC spokesperson said they “removed the mask recommendation from the monkeypox Travel Health Notice because it caused confusion.” 

This change in advice appears to reflect the stance that monkeypox is primarily spread by up-close and direct contact. However, there is some evidence that the virus can be spread through aerosolized airborne transmission, at least over a short distance. 

Monkeypox is endemic in parts of central and western Africa, but an ongoing and unusual outbreak has seen over 1,000 confirmed and suspected cases reported in 29 countries.

The virus that causes monkeypox is part of the same family as smallpox. Symptoms of monkeypox are also similar to smallpox – albeit milder – with patients experiencing fever, achy muscles, swollen lymph nodes, exhaustion, and a rash. More visible symptoms like unusual rashes, lesions, and scabs on the skin appear later. 

Meanwhile, another corner of the CDC website still advises people with monkeypox to wear a surgical mask, especially if they are experiencing respiratory symptoms such as a cough or sore throat. It also says people living in the same household as an infected person should consider wearing a mask to protect themselves. 

Some have pointed out that this flip-flopping is reminiscent of the early confusion over whether SARS-CoV-2, the virus that causes COVID-19, should be considered airborne. In the opening stages of the pandemic, the World Health Organization (WHO) repeatedly stressed that COVID-19 was not airborne or spread by aerosol transmission. It transpired they were gravely wrong – it’s now well-established that airborne transmission is one of the most important ways that COVID-19 spreads to person-to-person.

Monkeypox is a very different disease from COVID-19. While there is evidence of some airborne transmission, it currently appears that the virus is primarily spread through direct contact with infectious sores, scabs, or body fluids. This includes spit and sneezes, plus the inhalation of aerosolized viruses, but lingering airborne particles are not considered to be the most significant route of transmission. 

As per the CDC's latest advice, avoiding direct and up-close contact with an infected person is still the most important way to prevent the spread of monkeypox. 

The question of how masks and airborne transmission factor into this is likely to be a subject of continued debate.