Smallpox: Key Facts, History, Transmission, Symptoms, Diagnosis & Treatment

Table of Contents

What is Smallpox?

Smallpox is highly fatal and contagious disease caused by Variola virus, a member of orthopoxvirus family.
The term smallpox was first used in Europe in the 15^th century to differentiate Variola from the “great pox” (syphilis)
It is caused by Variola virus and is known to be the most devastating disease known to mankind which millions of deaths before its eradication
Smallpox is a contagious, disfiguring and deadly disease.
Naturally occurring smallpox was eradicated from world in 1980 by unprecedented global immunization campaigns
The samples of smallpox are preserved in the laboratories for research purposes

Key Facts

The origin of smallpox is still unknown but presence of smallpox like rashes in the Egyptian mummies suggested its existence from 3000 years.
An estimated 300 million people died from smallpox in the 20^th century alone
As the world population grew and travel increased the virus grasped every opportunity to colonize world
The survivors of the disease became immune to the disease. As a result physicians intentionally infected healthy person with smallpox virus. Thus vaccine was developed
Though smallpox is eradicated, it still poses a threat as most devastating biological weapons due to its specimen being preserved in the research laboratories
Smallpox causes high fever, prostration, and a characteristic rash. The rash usually includes blister-like lesions that occur everywhere on the body.
Approximately one-third of people with smallpox died from the disease. Survivors were scarred for life. If the eye was infected, blindness often resulted.
The smallpox vaccine, created by Edward Jenner in 1796, was the first successful vaccine to be developed.

History of Smallpox

6^th Century—Increased trade with China and Korea brings smallpox to Japan.
7^th Century—Arab expansion spreads smallpox into northern Africa, Spain, and Portugal.
11^th Century—Crusades further spread smallpox in Europe.
15^th Century—Portugal occupies part of western Africa, bringing smallpox.
16^th Century—European settlers and the African slave trade import smallpox into:
- The Caribbean
- Central and South America
17^th Century—European settlers bring smallpox to North America.
18^th Century—Explorers from Great Britain bring smallpox to Australia.

Mode of Transmission

Face to face contact/directly from person to person: through air by droplets during coughing, sneezing, talking etc.
Direct contact with infected fluids and contaminated objects
Via contaminated items: can spread through contaminated clothing, bedding. However, risk of infection through this is less common.
Vertical transmission incidence is low but the virus can cross the placenta
Transmission doesn’t happen from animals or vectors

Incubation Period

The incubation period of smallpox is usually 7-17 days. i.e., the first symptoms of smallpox usually appear 7-17 days after a person is infected with the virus. During this period, the virus is not contagious.

Signs and Symptoms

Initial symptoms/prodome stage last for about 2-4 days which is sometime contagious.
- High fever
- Malaise
- Headache
- Severe fatigue
- Severe backpain and
- sometime vomiting occurs
Early rash stage which lasts for 4 days where there is appearance of small red spots on tongue and in mouth. These spots develop in sores and burst to spread large amount of virus. It is the most contagious stage
Pustular rash and scab stage that last for 10 days. The sore turns into pustules and after 5 days it begins to form crust and scab
The scabs fall off after three weeks of rash appearance and leaves behind the scar
After the four weeks rash appears all the scabs falls off. Only after all the scabs falls off it is no more contagious

Diagnosis

Physical examination of signs and symptoms include a skin and mouth exam to look for smallpox rash
Lab test in case of high suspicion
Test are conducted only on specially protected laboratories with biosafety level 4
Lab test includes PCR, ELISA, Immunohistochemistry and electron microscopy

Prevention and Treatment of Smallpox

There is no proven treatment for smallpox but there are certain antiviral drugs such as tecovirimat, brincidofovir, etc. to work against smallpox virus
Patients with smallpox can benefit from supportive therapy such as wound care, infection control, fluid therapy and antibiotics for any secondary infection
Smallpox can be highly prevented from smallpox vaccine named as vaccinia virus vaccine
Preventive measures to control the spread of smallpox also include isolating the person who had smallpox
Vaccination within 3 days or before being exposed can protect against the disease.
Even if vaccine is administered within 4-7 days of being exposed can significantly reduce the severity of disease

Complications

There are few instances where smallpox causes complications.
People who recover from smallpox usually have severe scars, especially on the face, arms and legs.
In some cases, smallpox may cause blindness.

Vaccine of Smallpox

Prevention of smallpox rests on two pillars i.e., vaccination and isolation of the patient if they develop fever.
The smallpox vaccine contains live vaccinia virus and has sideeefcts but doesn’t give smallpox
Smallpox vaccine provides high level immunity 3 to 5 years and decreasing immunity there after
Historically, smallpox vaccine has effectively prevented the infection in 95% of those vaccinated
The vaccine is usually given in upper arm and red and itchy bump appearance with 3 to 4 days indicates successful vaccination

Strategies Used for Eradication of Smallpox

Strategies used for eradication of smallpox included two-fold strategy:

Mass vaccination
Development of surveillance system

1. Mass vaccination

Campaigns in every country was started to reach at least 80% of the population
Through the use of vaccination guns, government resources and traditional health authorities, large numbers of people were vaccinated
Over 100 million vaccine were administered in a 5 year period
90% of the population had been vaccinated and smallpox rated fell due to these efforts
Ring vaccination as key strategy for global eradication program
great impact on smallpox transmission even in areas where overall vaccination coverage was low by using a strategy called surveillance and containment, or ring vaccination
the principle behind this strategy was to identify cases of smallpox
vaccination of these households and other close contacts
if the primary contacts developed smallpox despite vaccination, their close contacts would already be safe and chain of transmission would be broken

2. Development of surveillance system

Special surveillance teams were recruited and trained to search for smallpox cases and vaccinate their close contacts
They visited each health unit in an area of endemic smallpox to ensure that each week the health officer submitted a report indicating the number of cases seen
When the cases were reported, the teams worked with local health staff to find additional cases and to contain the outbreaks by vaccinating the contacts
Even after setbacks this surveillance and containment strategy proved to be the strategy that finally brought about the eradication of smallpox throughout the world

Eradication of Smallpox

Smallpox was eradicated from the world on May 8, 1980
Almost two centuries after Jenner hoped that vaccination could annihilate smallpox, (33^rd) World Health Assembly declared the world free of Smallpox disease on May 8, 1980.

Stock of Variola Virus/Smallpox Virus

Although smallpox is eradicated from the world, the stock of variola virus is still safely stored in couple of laboratories of the world.
After the eradication of smallpox, scientists and public health professionals decided to keep the stock of variola virus for further research and investigation.
In 1981, there were four countries viz. United States, England, Russia and South Africa, which served as a WHO collaborating center that were actively working with Variola virus.
By 1984, England and South Africa closed their labs by either destroying their stocks or transferring it to other approved labs.
Currently, there are only two locations that officially store and handle variola virus under WHO supervision. They are:
The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, United States and
The State Research Center of Virology and Biotechnology (VECTOR Institute) in Koltsovo, Russia.