LACMA-Blog | CDC Health Advisory: Monkeypox virus infection in the
Since May 14, 2022, clusters of monkeypox cases have been reported in several countries that do not normally have monkeypox. Although previous cases outside of Africa have been associated with travel from Nigeria, most recent cases do not pose direct exposure risks associated with travel. The UK Health Security Agency (UKHSA) was the first to announce on 7 May 2022 the identification of a recent case in the UK which occurred in a traveler returning from Nigeria. On May 14, 2022, UKHSA announced an unlinked cluster of monkeypox cases in two people living in the same household who have no recent travel history. On May 16, 2022, UKHSA announced a third cluster of time-clustered cases involving four people who identify as gay, bisexual or men who have sex with men (MSM), none of whom are related with the three previously diagnosed patients. Some evidence suggests that cases among MSM may be epidemiologically linked; patients in this group were identified at sexual health clinics. This is an evolving investigation and public health authorities hope to learn more about exposure routes in the coming days.
Monkeypox is an endemic zoonotic infection in several countries of central and western Africa. The wildlife reservoir is unknown. Prior to May 2022, cases outside of Africa were reported either among people with recent travel to Nigeria or in contact with someone infected with monkeypox virus. However, as of May 2022, nine patients have been confirmed with monkeypox in England; six were among people with no history of travel to Africa and the source of these infections is unknown.
Symptoms of monkeypox disease always involve the characteristic rash, whether or not there is a disseminated rash. Historically, the rash has been preceded by a prodrome including fever, lymphadenopathy, and often other nonspecific symptoms such as malaise, headache, and muscle aches. In more recent reported cases, prodromal symptoms may not always have occurred; some recent cases began with characteristic monkeypox-like lesions in the genital and perianal region, in the absence of subjective fever and other prodromal symptoms. For this reason, cases may be confused with more common infections (eg, syphilis, chancroid, herpes, and varicella-zoster). The average incubation period for the onset of symptoms is 5 to 13 days.
Typical monkeypox lesions involve the following: deep, well-circumscribed lesions, often with central umbilication; and the progression of the lesion through specific sequential stages – macules, papules, vesicles, pustules and crusts. Synchronized progression occurs at specific anatomical sites with lesions at each developmental stage for at least 1-2 days. The scabs eventually fall off1. Lesions can occur on the palms and soles of the feet and when generalized the rash is very similar to that of smallpox, including a centrifugal distribution. Monkeypox can occur alongside other skin rashes, including varicella zoster virus and herpes simplex virus infections. The lethality of monkeypox would be between 1 and 11%. Laboratory confirmatory diagnostic testing for monkeypox is performed using a real-time polymerase chain reaction assay on lesion-derived specimens.
A person is considered contagious when symptoms appear and is presumed to remain contagious until the lesions have crusted over, the crusts have separated, and a new layer of healthy skin has formed underneath . Human-to-human transmission occurs through large respiratory droplets and through direct contact with bodily fluids or lesion material. Respiratory droplets generally cannot travel more than a few feet, so prolonged face-to-face contact is required. Indirect contact with lesion material by fomites has also been documented. Transmission from animals to humans can occur through a bite or scratch, preparation of wild game, and direct or indirect contact with bodily fluids or lesion material.
There is no specific treatment for monkeypox virus infection, although antivirals developed for use in patients with smallpox may prove beneficial2. Individuals with direct contact (eg, exposure to skin, scabs, bodily fluids, or other materials) or indirect contact (eg, being within six feet in the absence of an N95 or air-purifying respirator for ≥ 3 hours) with a patient with monkeypox should be monitored by health services; depending on their level of risk, some individuals may be candidates for post-exposure prophylaxis with smallpox vaccine as part of an investigational new drug protocol after consultation with public health authorities.