U.S. health officials say they have identified a cluster of cases in five states caused by a variant of the highly dangerous mpox virus that is linked to Siga Technologies’ antiviral Tecovirimate, branded as TPOXX.

At least 18 people were infected with clade II mpox between Oct. 6, 2023, and Feb. 15, 2024, according to the Morbidity and Mortality Weekly Report from the Centers for Disease Control and Prevention — and none of them had ever received treatment before. . Experts say cases of clade II mpox are endemic to West Africa – which sparked a global outbreak in 2022 and prompted the World Health Organization to declare it a public health emergency this year.

MPox cases are spreading at low levels in many countries, especially in DR Congo.

An earlier cluster was reported in California last year

These drug-resistant MPox cases follow an initial, unrelated cluster reported in California in early 2023 and are the first cases to involve multiple states, the report said. Health officials said the latest cases were not taken seriously at first because genetic sequencing is not done on all Mpox cases to determine the type that causes infection.

According to the study authors, round-the-clock surveillance is needed to monitor the emergence of drug resistance to safeguard the effectiveness of the stockpiled antiviral drug TPOX for smallpox preparations. It is also used to treat other orthopoxvirus infections, including mpox.

The report said CDC officials advised doctors to closely follow protocols for the use of TPOXX, and make sure patients take the drug properly. The findings also emphasize the need for additional MPOX treatments.

What is a clade II strain of mpox?,

Three groups of mpox viruses are recognized by WHO – Clade I is present in the Congo Basin and causes up to 10 percent of human deaths. It is usually spread through rodents and rarely from human-to-human. Clade II is in West Africa – and has a low mortality rate.

Clade IB is more contagious than Clade II and capable of being more severe, experts say, so infectious disease experts are concerned about its further international spread.

US evaluating use of TPOXX in clade 1B cases

According to the report, the study evaluated the use of TPOXX in clade 1b cases and resulted in the treatment not being effective in helping patients recover more quickly than a dummy treatment.

Mpox is a viral infection that causes flu-like symptoms and pus-filled sores. Although usually mild, the virus can be fatal in some individuals with weakened immunity. Mpox is spread through close physical contact, including sexual contact.

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