Related Topic

Thursday, January 25, 2007

Smallpox -- FAQs

What is smallpox?

Smallpox is an ancient and acute contagious disease caused by Variola virus, a member of the orthopoxvirus family. Smallpox (also known by the Latin names Variola or Variola vera) is a highly contagious viral disease unique to humans. It is caused by either of two virus variants named Variola major and Variola minor. V. major, the deadlier form, has a mortality rate of 20–40 percent, while V. minor kills 1% of its victims. Other long-term effects usually include skin scars and occasionally include blindness due to corneal ulcerations.

Virus classifications are:

  • Group: Group I (dsDNA)
  • Family: Poxviridae
    Genus: Orthopoxvirus
    Species: Variola vera

Smallpox was fatal in up to 30% of cases. Smallpox has existed for at least 3,000 years and was one of the world’s most feared diseases until it was eradicated by a collaborative global vaccination programme led by the World Health Organization. The last known natural case was in Somalia in 1977. Since then, the only known cases were caused by a laboratory accident in 1978 in Birmingham, England, which killed one person and caused a limited outbreak. After successful vaccination campaigns throughout the 19th and 20th centuries, the World Health Organization (WHO) certified the eradication of smallpox in 1979.

Smallpox was responsible for an estimated 300–500 million deaths in the 20th century. As recently as 1967, the World Health Organization (WHO) estimated that 15 million people contracted the disease and that two million died in that year.

What are the symptoms of smallpox?

The symptoms of smallpox begin with high fever, fatigue, head and body aches, and sometimes vomiting. The virus then produces a characteristic rash, particularly on the face, arms and legs. The resulting spots become filled with clear fluid and later, pus, and then form a crust, which eventually dries up and falls off., after about three weeks, leaving a pitted scar.

Does it occur naturally?

Smallpox no longer occurs naturally since it was totally eradicated by a lengthy and painstaking process, which identified all cases and their contacts and ensured that they were all vaccinated. Until then, smallpox killed many millions of people.

If someone comes in contact with smallpox, how long does it take to show symptoms?

The virus which causes smallpox is contagious and spreads through person-to-person contact and saliva droplets in an infected person’s breath. It has an incubation period of between 7 and 17 days after exposure and only becomes infectious once the fever develops. A distinctive rash appears two to three days later. The most infectious period is during the first week of illness, although a person with smallpox is still infectious until the last scabs fall off.

Is smallpox fatal?

The majority of patients with smallpox recover, but death may occur in up to 30% of cases. Many smallpox survivors have permanent scars over large areas of their body, especially their face. Some are left blind

How fast does smallpox spread?

The speed of smallpox transmission is generally slower than for such diseases as measles or chickenpox. Smallpox normally spreads from contact with infected persons. Patients spread smallpox primarily to household members and friends because by the time patients are contagious, they are usually sick and stay in bed; large outbreaks in schools were uncommon.

Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from one person to another. Smallpox also can be spread through direct contact with infected bodily fluids or contaminated objects such as bedding or clothing. Indirect spread is less common. Rarely, smallpox has been spread by virus carried in the air in enclosed settings such as buildings, buses, and trains. Smallpox is not known to be transmitted by insects or animals.

If smallpox is released in aerosol form, how long does the virus survive?

The smallpox virus is fragile. In laboratory experiments, 90% of aerosolized smallpox virus dies within 24 hours; in the presence of ultraviolet (UV) light, this percentage would be even greater. If an aerosol release of smallpox occurs, 90% of virus matter will be inactivated or dissipated in about 24 hours.

Weren’t the remaining stocks of the smallpox virus destroyed after smallpox was eradicated?

When smallpox was officially certified as eradicated, in December 1979, an agreement was reached under which all remaining stocks of the virus would either be destroyed or passed to one of two secure laboratories – one in the United States and one in the Russian Federation. That process was completed in the early 1980s and since then no other laboratory has officially had access to the virus which causes smallpox.

Then why is smallpox being talked about now?

Some governments believe there is a risk that the virus which causes smallpox exists in places other than these laboratories and could be deliberately released to cause harm. It is impossible to assess the risk that this might happen, but at their request, WHO is making efforts to help governments prepare for this possibility.

Is there any treatment for smallpox?

There is no cure for smallpox, but vaccination can be used very effectively to prevent infection from developing if given during a period of up to four days after a person has been exposed to the virus. This is the strategy that was used to eradicate the disease during the 20th century.

There is no proven treatment for smallpox, but research to evaluate new antiviral agents is ongoing. Early results from laboratory studies suggest that the drug cidofovir may fight against the smallpox virus; currently, studies with animals are being done to better understand the drug's ability to treat smallpox disease. Patients with smallpox can benefit from supportive therapy (e.g., intravenous fluids, medicine to control fever or pain) and antibiotics for any secondary bacterial infections that may occur.

Is a vaccine currently available?

There is a vaccine against smallpox and it was a key tool in the eradication of the disease. The vaccine does not contain the Variola virus which causes smallpox , but a closely related virus called vaccinia. When this vaccine is given to humans, it protects them against smallpox. However, it can have very serious side effects, which in extreme cases can be fatal. It has therefore not been recommended for the general public since smallpox was eradicated. It is used to protect researchers who work on the variola virus that causes smallpox and other viruses in the same virus family (known as orthopox viruses). It could also be used to protect anyone else judged to have a high risk of exposure to smallpox. The vaccine cannot be used in people whose immune systems are not functioning properly.

Should the smallpox vaccine be widely used to protect people?

Vaccination with the vaccinia virus as a protection against smallpox is not recommended for widespread use. No government gives or recommends the vaccine routinely since it can cause serious complications, and even death. It should be given only to those persons who have a high risk of coming into contact with the virus which causes smallpox, or who have been exposed.

What can be done to protect people from smallpox?

Doctors, health workers and hospital personnel around the world have been trained to identify infectious diseases, verify their diagnosis and then respond accordingly. The same system would identify any possible outbreak of smallpox even if the virus is deliberately spread to cause harm. The public health system would then be mobilized to trace all known contacts of the infected person and vaccinate them to prevent more cases of smallpox from developing. If this is done rapidly and effectively, the number of cases could be kept to a minimum and the outbreak would be contained. This was the approach which successfully eradicated the disease. The key is a good disease detection system and a rapid response to infectious diseases, no matter what their cause. At this time, several governments have started to examine the potency and levels of their smallpox vaccine stocks, and to consider whether, and under what circumstances, to obtain additional supplies.

I had the vaccination when I was a child. Am I still protected?

Anyone who has been vaccinated against smallpox (in most countries, this means anyone aged 25-30 or over) will have some level of protection. The vaccination may not still be fully effective, but it is likely to protect you from the worst effects of the disease. However, if you were directly exposed to the virus which causes smallpox, a repeat vaccination would be recommended.

No comments: