Smallpox transmission

How many people would have to get smallpox before it is considered an outbreak One suspected case of smallpox is considered a public health emergency. Smallpox surveillance in the United States includes detecting a suspected case or cases, making a definitive diagnosis with rapid laboratory confirmation at CDC, and preventing further smallpox transmission. A suspected smallpox case should be reported immediately by telephone to state or local health officials. They should immediately obtain advice regarding isolation of the patient or patients, and on laboratory specimen collection. State or local health officials should notify CDC immediately at (404) 639-2184 or (404) 639-0385 if a suspected case of smallpox is reported. 

Right now, we have to deal with incubation time and wait for victims to develop symptoms. The incubation time for anthrax is one to six days. In this example, anthrax victims would have one to six days between exposure and the onset of symptoms. Anthrax is not transmissible from person to person. Compare this to the incubation time with that of the virus, smallpox, which is ten to seventeen days. Smallpox is highly transmissible from person to person. After exposure to smallpox, a person could travel by air around the world a number of times and contaminate many people before developing any symptoms. However, naturally occurring smallpox has been eradicated worldwide since 1977. Terrorism could rapidly change that eradication to an attack since samples of the smallpox virus have been stored in both the United States and Russia. 

In the majority of cases, smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. People with smallpox are most infectious during the first week of illness, because that is when the largest amount of virus is present in saliva. However, some risk of transmission lasts until all scabs have fallen off. 

Transmission of smallpox virus rarely occurs before the appearance of the rash that develops 2-4 days after the initial fever. 

Smallpox Virus transmissible via large or small respiratory droplets or contact with skin lesions and secretions. 

In 1621 smallpox came to North America from a ship sailing from the West Indies. This importation of smallpox was not, of course, the first or even the most lethal transmission of the disease to the continent. When the indigenous peoples of the New World initially encountered this Old World disease, the impact was far more horrific (McNeil 1976). Smallpox, like other diseases, has the potential to wipe out civilizations. 

Domestic animals have been incredibly useful for discovering novel approaches to combat major disease problems in humans for centuries. Without question, the most notorious infectious disease of all time with a prominent skin lesion was smallpox. Descriptions by Barron (1) remind us of the severity of the skin disease, even though the viral infection involved many other organs. Jenner s controversial work, first published in 1798, based on interspecies transmission of cowpox or, more likely, horsepox, from its natural host to human caretakers who subsequently were immune to smallpox infection lead to the development of vaccines (derived from the Latin word vaccinus, which means relating to a cow)... 

All patients in whom smallpox is suspected should be placed in strict respiratory isolation in negative pressure rooms. Contacts of patient should be vaccinated and placed under surveillance. Isolated in-home or nonhospital facilities are preferable, due to the high risk of transmission of smallpox via aerosol within hospital environments (Henderson et al., 1999). 

Smallpox spread slower than other viral rash illnesses like chickenpox and measles. When smallpox still occurred naturally, most people who became infected were close contacts of an index case, snch as household members, close friends and health care workers. Honsehold secondary attack rates were typically 50-60% (25). Larger ontbreaks in schools were nncommon. Two reasons for this are that that transmission did not occnr before rash onset and that the disease caused severe incapacitation. By the time of rash onset, victims were so ill that they did not attend school or go to other commnnity events where they might have exposed others. Secondary cases typically occnrred in hospital and household contacts. 

During the global eradication program, pnblic health workers were able to interrupt disease transmission by isolating smallpox patients so their contact was limited to people who had already had the disease or were previously vaccinated (25). hi addition, public health workers identified contacts, immediately vaccinated them, and monitored them closely, isolating them if they became ill to prevent additional... 

A smallpox attack wonld pose difficult problems for public health officials due to the ability of the virus to continue to spread unless stopped by isolation of patients and vaccination/isolation of their close contacts (26). Given the threat of aerosol transmission in hospitals, as the number of cases rises, physicians should isolate suspected patients in their homes or an alternative nonhospital facility. Such home care is reasonable, considering that supportive therapy is the only care available to smallpox victims (26). Chapter 6 discusses alternative treatment centers that public health authorities are likely to establish during large outbreaks. 

Inadvertent inoculation, the most frequent complication of smallpox vaccination, refers to the transmission of the vaccinia virus from the inoculation site to another part of the recipient s body (autoinoculation) or to the bodies of close contacts (Fig. 2.8 see color plate 2.8). It can occur because live vaccinia virus is present at the inoculation site from about 4 days after inoculation until the crust separates from the skin. Maximum viral shedding occurs 4-14 days after inoculation. Inadvertent inoculation is responsible for approximately half of all complications for primary vaccination and revaccination. Because inadvertent inoculation frequently results from touching the vaccination site and transmitting the virus manually, the most common affected sites are the face, eyelid, nose, mouth, genitalia, and rectum. Most cases heal without any specific treatment. Inadvertent inoculation of the eye can lead to comeal scarring and subsequent vision loss. Occasionally, vaccinia immune globulin (VIG) is necessary to treat periocular lesions (26). 

Specifically, the ACIP has recommended that each state and territory establish and maintain at least one smallpox response team of vaccinated individuals. Having such smallpox response teams fits with the primary strategy to control a smallpox outbreak through surveillance and containment, which includes case isolation and vaccination of persons at risk for exposure. This strategy, which proved effective in eradicating naturally occurring smallpox, includes identification of cases through intensive surveillance, isolation of cases to prevent further transmission, vaccination of primary contacts (household contacts and other close contacts of cases) and vaccination of secondary contacts (close contacts of the primary contacts) (32). 

Agent Index A336 Class Index C24 Smallpox Type Virus Initial symptoms are flulike including headache, chills, high fever (106° to 107°F), and aches in back and limbs. An Initial macular rash appears progressing to papules, and then blisters. The blisters in turn form crusts. The blisters and crusts cause severe itching. Routes Inhalation Abraded Skin Mucous Membranes Secondary Hazards Aerosol Contact Body Fluids Fomites Incubation 7 to 16 days Mortality Rate < 35% Reservoir Humans Direct Person-to-Person Transmission is possible. 

In between, a sort of bioterrorism came to the New World in the fifteenth century, aimed to defeat the Indians. Spanish conquistador Pizarro gave clothing contaminated with the smallpox virus to natives in South America. During the French and Indian War (1754-1767) Sir Jeffrey Amherst, commander of British forces in North America, suggested the deliberate use of smallpox to reduce Native American tribes hostile to the British [116]. An outbreak of smallpox at Fort Pitt results in the opportunity to execute Amherst s plan. On June 24, 1763, Captain Ecuyer, Amherst s subordinate, gives blankets and a handkerchief from the smallpox hospital to the Native Americans and records in his journal, I hope it will have the desired effect. This was followed by an epidemic of smallpox among Native American tribes in the Ohio River valley, which may also have been spread by contact with settlers. Transmission of smallpox by fomites (on blankets) is inefficient compared with respiratory droplet transmission. 

A naturally occurring relative of variola, monkeypox virus, is found in Africa, and the disease it causes, monkeypox, is clinically indistinguishable from smallpox, with the exception of notable enlargement of cervical and inguinal lymph nodes. The disease occurs mostly in monkeys from the tropical rain forests of central Africa, with sporadic transmission to humans. Some evidence supports the role of squirrels as the principal animal reservoir of the virus.48 Over a span of 3 years, 331 cases of monkeypox disease in a population of 5 million have been reported.49 Under natural conditions, the virus is transmitted by direct contact with an infected individual, fomites, and, occasionally by aerosol. 

Noble J, Rich JA. Transmission of smallpox by contact and by aerosol routes in Macaca irus. Bull WHO. 1969 40 279-286. 

None, no evidence of person to person transmission pneumonic plague For 72 hrs, following initiation of appropriate antimicrobial therapy or unUl sputum culture is negative Smallpox approximately 3 weeks, usually corresponds with the initial appearance of skin-lesions to their final disappearance, most infectious during the first week of rash via inhalation of virus released from oropharyngeal-lesion secretions of the index case VHF varies with virus, but at minimum, all for the duration of illness and for Ebola Marburg transmission through semen may occur up to 7 weeks after clinical recoverv. 

Isolate patients with suspected plague, smallpox, or viral hemorrhagic fevers, who may be highly contagious. Patient isolation is not needed for suspected anthrax, botulism, or tularemia since person-to-person transmission is not likely. However, health care workers should always use universal precautions. 

With the exception of smallpox virus and to a lesser extent plague bacteria, person-to-person transmission of these diseases rarely occurs if "universal precautions" are maintained (e.g., gloves, gown, mask, and eye protection). The majority of infected patients can be cared for without specialized isolation rooms or specialized ventilation systems. Cohort nursing with the usual practice of universal precautions will provide adequate protection. The hemorrhagic virus infections may be transmissible via a respirable aerosol of blood— respiratory protection of workers caring for these patients is required. 

The occurrence of laboratory-acquired infections in research workers is not the only problem in biosafety. The other major concern is the potential for release of infectious agents that may cause secondary infections in nonlaboratory workers and other contacts. Fortunately, the potential for such serious outbreaks of laboratory-acquired disease seems to be small. Data derived from studies at the U.S. Department of Agriculture National Animal Disease Center showed that, during the years from 1960 to 1975, no instances of secondary infection in other laboratory workers or in nonlaboratory contacts occurred as the result of the laboratory-acquired infections of 18 research workers who used animal pathogens that were also infective for humans (448). However, the potential for outbreaks of laboratory-associated disease does exist as there are reports in the literature of instances of secondary transmission of laboratory-acquired Marburg disease (283), Q fever (38), and smallpox (105,518). Fortunately, the low level of occurrence of such incidents suggests that... 

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