A more serious type of mpox may be spreading in California. Three people in the state were hospitalized with the virus. None of them had recently traveled outside the country. California public health officials agree that this suggests local person-to-person transmission. There was a large outbreak of mpox in this country in 2022, but it involved a different type of virus that is less likely to cause serious health problems.
Types of Mpox
Mpox is related to the smallpox virus. Researchers have identified two main types of the virus called clade I and clade II. The global outbreak in 2022 was caused by a clade II type. Most cases in this outbreak were transmitted among men who have sex with men (MSM) through sexual activity and intimate physical contact. Clade II mpox usually causes mild infections and has a mortality rate of less than 1%.
Clade I mpox causes more severe disease and has a mortality rate of about 10%. This type of virus has been found in the Democratic Republic of Congo (DRC) for many years. Until recently, most cases passed directly from animals to humans through butchery and food. A new outbreak that started in the DPRK in 2023 is spreading from person to person.
In some parts of Africa, this clade I virus is transmitted between family members through daily household activities. It is also spread in patient care areas when proper protective equipment is not available. Many incidents involving children under the age of 15 have been reported in these areas.
In other areas, sexual transmission is more common. This is the first time clade I mpox has been sexually transmitted. Most cases are transmitted through heterosexual sex. Many cases have been seen in sex workers, truck drivers and other transient workers.
Current Clade I epidemic
There have been more than 40,000 cases of clade I mpox in several Central and East African countries. There have also been cases in other countries, but most have been in people who had recently traveled to Africa.
Until now, only six cases of clade I mpox had been reported in the United States. All of them were in people who had recently traveled. The three new cases in California — one in Long Beach and two in Los Angeles County — involve people who have not traveled recently. Public health officials could not find a direct link between them. This suggests local spread.
Public health officials are working closely to identify possible sources of transmission. They are also working to understand how serious this type of virus can become here. It is possible that access to better health care means better outcomes for outbreaks in this country than in other parts of the world.
Mpox prevention
The risk of clade I mpox remains low in the US, but experts want health care providers to be on the lookout for mpox symptoms. People at higher risk for mpox should also remain vigilant. It is also important to remember that there are still cases of clade II mpox in the US, although the numbers are much lower than they were in 2022.
There is a vaccine called JYNNEOS that can prevent mpox. The CDC recommends the vaccine for:
Gay, bisexual, transgender or other men who have sex with men who have had (in the past six months) or expect to:
- One or more sexually transmitted infections
- More than one sexual partner
- Anonymous sexual or intimate contact
- Sex in a sex shop
- Sex in conjunction with a large public event in a geographic area where mpox transmission occurs
In addition to recommending that everyone who meets these criteria get vaccinated, the CDC has issued safer-sex guidelines specifically for mpox. The guidelines remind people that the virus is spread through close face-to-face contact as well as contact with blisters and any cloth that has touched the blisters.
During the 2022 outbreak, gay, bisexual, transgender, another MSM changed some of their attitudes. They cut down on anonymous sex, had less skin-to-skin contact, and washed all the bedding right away. These and other changes were credited with keeping infections lower.
While the risk of a new mpox outbreak remains low in this country, it is important to stay informed and prepared. We must do everything we can to prevent transmission, especially with this most dangerous type.
