Smallpox infection control

Pre-1900 Treatment of rabies, anthrax, and smallpox Principles of infection control and pain relief Management of heart failure... 

If faced with a high-risk case, or in a limited smallpox outbreak, physicians should take immediate action to alert infection control at the hospital and institute contact precautions and respiratory isolation. These include (25) ... 

Patients having a febrile prodrome and either one other major criterion or at least four minor criteria are at moderate risk for smallpox. For patients at moderate risk, physicians should alert infection control and immediately institute contact precautions and respiratory isolation. If possible, they should obtain dermatology and/or infectious disease consultation and obtain digital photographs of the lesions. Given a moderate risk situation, the appropriate clinical diagnosis is essential, and physicians must rule out varicella or complication of vaccinia (smallpox vaccine). Therefore, for moderate risk patients, the history is essential, specifically the history of clinical varicella infection, history of vaccination for varicella and history of possible exposure to vaccinia (smallpox) vaccine. 

However, because of the possibility of a smallpox attack, albeit remote, in December 2002 President Bush announced his preevent vaccination plan. Instead of mass vaccination, the plan, based on recommendations from the CDC, the Advisory Committee on Immunization Practices (ACIP) and the Healthcare Infection Control Practices Advisory Committee (HICPAC) makes smallpox vaccination available for people designated by public health authorities to conduct investigation and follow-up of initial... 

A live vaccine strain of measles (Chapter 15) was introduced in the USA in 1962 and to the UK in 1968. A single injection produces high-level immunity in over 95% of recipients. Moreover, since the vaccine induces immunity more rapidly than the natural infection, it may be used to control the impact of measles outbreaks. The measles virus cannot survive outside ofan infected host. Widespread use ofthe vaccine therefore has the potential, as with smallpox, of eliminating the disease worldwide. Mass immunization has reduced the incidence of measles to almost nil, although a 15-fold increase in the incidence was noted in the USA between 1989 and 1991 because of poor compliance. 

There is no proven treatment for smallpox, but in persons exposed to smallpox who do not show symptoms as yet, the vaccine — if given within four days after exposure — can lessen the severity of or even prevent illness. However, once a patient shows symptom, treatment is limited to supportive therapy and antibiotics to treat bacterial infections. Patients with smallpox can benefit from supportive therapy such as intravenous fluids, and medicines to control fever or pain. 

Three basic approaches are used to control viral diseases vaccination, antiviral chemotherapy, and stimulation of host resistance mechanisms. Vaccination has been used successfully to prevent measles, rubella, mumps, poliomyelitis, yellow fever, smallpox, chickenpox, and hepatitis B. Unfortunately, the usefulness of vaccines appears to be limited when many stereotypes are involved (e.g., rhinoviruses, HIV). Furthermore, vaccines have little or no use once the infection has been established because they cannot prevent the spread of active infections within the host. Passive immunization with human immune globulin, equine antiserum, or antiserum from vaccinated humans can be used to assist the body s own defense mechanisms. Intramuscular preparations of immune globulin may be used to prevent infection following viral exposure and as replacement therapy in individuals with antibody deficiencies. Peak plasma concentrations of intramuscular immune globulins occur in about 2 days. In contrast, intravenously administered immune globulin provides immediate passive immunity. 

Vaccination programmes have been very effective in the control of some viral diseases. Protection against smallpox was first demonstrated in 1796 by Jenner by inoculation with cowpox. Smallpox was later successfully eradicated. Poliovirus is also being eliminated thanks to a controlled intensive worldwide vaccination programme initiated by the World Health Organization. Such preventative methods are the most effective and economic way of controlling viral infections. 

Efforts were therefore made towards developing treatment strategies that might generate immunity to infection. An early development was the attempted control of smallpox (variola major) through the deliberate introduction, under the skin of healthy individuals, of material taken from active... 

According to the Centers for Disease Control, those potentially exposed to smallpox are individuals who have come into close contact with an infected person while that person is contagious, as well as household members of those who have come into close contact. "Close contact" means living in the same home as someone who has smallpox or spending at least three hours in the same room with someone who has smallpox... 

Vidarabine is used mainly in human HSV-1 and HSV-2 encephalitis, decreasing the mortality rate from 70 to 30%. Whitley et al. (57) reported that early vidarabine therapy is helpful in controlling complications of localized or disseminated herpes zoster in immunocompromised patients. Vidarabine also is useful in neonatal herpes labialis or genitalis, vaccinia virus, adenovirus, RNA viruses, papovavirus, CMV, and smallpox virus infections. Given the efficacy of vidarabine in certain viral infections, the U.S. FDA approved a 3% ointment for the treatment of herpes simplex keratoconjunctivitis and recurrent epithelial keratitis, and a 2% IV injection for the treatment of herpes simplex encephalitis and herpes zoster infections (Table 43.3). A topical ophthalmic preparation of vidarabine is useful in herpes simplex keratitis but shows little promise in herpes simplex labialis or genitalis. The monophosphate esters of vidarabine are more water-soluble and can be used in smaller volumes and even intramuscularly. These esters are under clinical investigation for the treatment of hepatitis B, systemic and cutaneous herpes simplex, and herpes zoster virus infections in immunocompromised patients. 

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