Gene sequencing efforts suggest that two different monkeypox variants are spreading in the U.S., raising the possibility that the virus has been circulating longer than experts initially thought, CDC officials said on Friday.
Currently, there have been 20 monkeypox cases identified in 11 U.S. states, all in adults, Jennifer McQuiston, DVM, deputy director of CDC's Division of High Consequence Pathogens and Pathology explained on a call with reporters. No deaths related to the virus have been reported to date, and all patients are in recovery or have recovered.
Most of these cases have been linked to international travel, and a majority that have been sequenced in the U.S. are linked to the variant reported in Europe, she said. However, a few genetic samples are different than the others sequenced in the U.S., in cases from people who recently traveled to West Africa and the Middle East. Both strains in the U.S. share common ancestors to variants that were present in Nigeria since 2017, McQuiston added.
McQuiston said that it is possible that some monkeypox cases in the U.S. previously went under the radar, "but not to a great degree." She added that to better understand how long the virus has been circulating, it will require analysis of "a lot more sequences from a lot more cases."
In a released on Friday, the CDC outlined the arc of the current monkeypox outbreak in the U.S., first detected in a Massachusetts resident on May 4. The report described 17 monkeypox cases as of May 31, 16 in men who have sex with men (MSM) and one in a woman. Nine states had detected monkeypox cases as of the end of May: California, Colorado, Florida, Georgia, Massachusetts, New York, Utah, Virginia, and Washington.
Patients with monkeypox typically present with a fever for 5 to 13 days, as well as body aches and fatigue. Between 1 and 4 days later, patients develop characteristic skin lesions. CDC officials stated that some cases are showing more subtle symptoms, such as fewer lesions that look similar to smallpox, which patients and healthcare providers should look out for.
The monkeypox strain linked to the current outbreak is the West African clade, which produces less severe illness than other variants, such as the Congo Basin clade.
The main risk factor for monkeypox is close contact with someone infected, specifically those who have monkeypox sores, McQuiston said. Although the majority of U.S. cases have been detected in patients who identify as gay, bisexual, or other MSM, CDC officials emphasized that the infection is not confined to this population, as the virus spreads through any prolonged, close physical contact.
The U.S. has two live-virus vaccines available to treat monkeypox -- Jynneos and ACAM2000 -- and an antiviral treatment called tecovirimat (TPOXX), said Dawn O'Connell, HHS assistant secretary for preparedness and response, during the briefing.
While O'Connell could not state specifics about the number of vaccines in the current supply for national security reasons, she said that "we have enough vaccine on hand to manage the current outbreak." O'Connell added that the U.S. has enough courses of antibiotics to treat those who are infected.
"While we need to remain vigilant and seek to contain the spread of monkeypox, the good news is that we already have the vaccines and treatments needed to respond," O'Connell said.
Raj Panjabi, MD, White House senior director for global health security & biodefense, said that to date, more than 120 PCR tests to detect orthopox viruses have been administered across the country. He added, however, that the nearly 70 labs that test for orthopox viruses in the Laboratory Response Network have the collective ability to perform more than 1,000 tests a day. Panjabi said officials are working to use that capacity, encouraging people to get tested if they have symptoms and urging healthcare providers to send in more tests.
Additionally, the federal government has delivered around 1,200 vaccines against monkeypox and 100 courses of treatment to eight jurisdictions.
Panjabi added that "infectious disease knows no borders," adding that the federal government is working to partner with other nations to curb the spread of illness.