Smallpox

 Smallpox (天花) is an acute, highly contagious infectious disease caused by the variola virus.  Infection is spread mainly via contact with respiratory droplets and body fluids or contaminated fomites. Patients will develop fever, headache, vomiting, etc. 12 to 14 days after infection. symptoms, and gradually develop dense red dot-like rashes and blisters on the face and limbs. The mortality rate among patients infected with malignant hemorrhagic smallpox exceeds 90%. However, through vaccination with cowpox vaccine, smallpox was officially declared eradicated by the World Health Organization in 1980. Check out the smallpox vaccine in Hong Kong. 

Types of smallpox 

There are 2 clinical forms of smallpox: Variola minor and Variola major 

1. Variola minor (also called Alastrim- Portugese for something that burns & spreads to places) – is caused by a less virulent form of the virus 

• Rash is indistinguishable from variola major but is less extensive 
• Case fatality rate is ~ 1% 

2.     Variola major (classic smallpox)– caused by the more virulent form of the virus

• Case fatality rate of 20-30% 
• Has 4 types according to clinical severity: 

• The most common type has symptoms such as fever, headache, back pain, chills and vomiting before the rash occurs. Comprised about 85% of cases. Deep blisters and pus bubbles will appear on the face and limbs successively. 

• Mostly occurred in people who have been vaccinated but still contracted the disease. The symptoms are the mildest. Headaches, backaches, etc. may also occur, but usually there is no fever, and the rash period is also very short. The rash is concentrated on the surface of the skin and heals quickly. 

• Presents with more severe initial symptoms as compared to ordinary smallpox. Common in young children. Skin lesions develop slowly, merge and remain flat and soft but never progress to the pustular (blister) stage. The process progresses slowly and may cause secondary viremia. The occurrence is very rare but with a very high fatality. 

• A severe form of the disease characterised by extensive bleeding in the skin, mucous membranes and internal organs. Typical pustules do not develop.Pregnant women are particularly more susceptible and prior vaccination does not offer protection. Case fatality rate is highest in both both unvaccinated and vaccinated patients reaching 100% in the early or fulminant form.  

Symptoms of smallpox    

Smallpox symptoms usually appear 12 to 14 days after infection and include: 

• fever 
• Headache 
• fatigue 
• severe back pain 
• Vomit 
• Flat red spots appear on the face, hands, and forearms, spreading to the torso 
• Within one to two days the spots will turn into small fluid-filled blisters, which turn into pus, and after 8 to 9 days they will scab over and eventually leave a dent. 
• Festering sores on the mucous membranes of the nose and mouth

How to diagnose smallpox 

The primary diagnostic criterion for smallpox is a fever ≥101°F (38.3°C) plus at least one of the following symptoms: 

• Collapse 
• Headache 
• Back pain 
• Chills 
• Vomit 
• Severe abdominal pain 
• Deep, firm, round, and well-circumscribed vesicles or pustules 

Secondary diagnostic criteria for smallpox: 

• Rash concentrated on face and extremities 
• Rash or sores on the mucous membranes of the mouth and roof of the mouth, face, or forearms 
• The patient is poisoned or on the verge of death 
• The rash evolves slowly, from macules to papules to pustules over several days 
• Lesions on the palms and soles of the feet 

Smallpox treatment  

There is currently no cure for smallpox. If an infection occurs, treatment focuses on relieving symptoms and preventing dehydration. If the patient also develops a bacterial infection in the lungs or skin, antibiotics may be required. 

How to prevent smallpox 

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