A lab worker accidentally injects a virus associated with smallpox into her finger

An employee of a laboratory accidentally injected the vaccinia virus into her finger. | Whitehouse ER / MMWR 2019 / CDC

An employee at a laboratory in San Diego, USA, accidentally injected the vaccinia virus (a virus associated with smallpox) into one of her fingers. The infection resulting from this accident caused the swelling and blackening of the finger, which took more than three months to heal.

According to the report relaying the accident, this case is quite unique, as this is the first time that doctors have used tecovirimat (a recently approved smallpox medication) to treat this condition. laboratory-acquired infection with vaccinia virus.

It should be known that the vaccinia virus is similar to the smallpox virus. However, vaccinia is less dangerous and does not cause smallpox. Moreover, vaccinia is the virus used to make smallpox vaccine: a global vaccination effort involving this vaccine led to the eradication of smallpox worldwide in 1980.

Although the vaccine is no longer widely used today, doctors prescribe it to people at risk of exposure to smallpox or similar viruses, such as scientists who work with the vaccine virus ( in research contexts, vaccinia virus can be used as delivery vector for gene or anticancer therapies).

But in the case described in this article, the female lab worker, a 26-year-old woman, involuntarily stabbed herself with a needle while performing an experiment forcing her to inject vaccinia virus into mice. . She immediately rinsed her finger with water for 15 minutes, warned her superiors and went to an emergency room.

Although the laboratory worker had the opportunity to receive the smallpox vaccine before starting work on vaccinia, she refused the vaccination. It is important to note that this smallpox vaccine has more side effects than most commonly offered vaccines today. Indeed, unlike most vaccines, which use weakened or killed viruses, the smallpox vaccine contains live vaccinia virus.

As a result, a few days after receiving the vaccine, people are expected to develop red and itchy lesions at the vaccination site. After that, the lesion turns into a large blister filled with pus. While the vaccination site is healing, it is necessary to cover it with a dressing that should be changed about every three days. Finally, a crust forms on the blister and falls, leaving a small scar. The whole healing process takes about three weeks. So it's not just a trivial vaccine.

An employee of a laboratory was accidentally infected with a smallpox-related virus: vaccinia virus. In this image, the detail of the employee's finger wound during the days and months following the accident. Credits: Whitehouse ER / MMWR 2019 / CDC

However, it should also be noted that despite these uncomfortable side effects, the vaccine has a very low risk of serious complications. On the other hand, accidental injection of vaccinia virus during laboratory work can lead to serious wound infections, which may require hospitalization.

In the case of this employee, about 10 days after the accident, she developed swelling and injury where the needle had planted. Later she had a fever and the swelling got worse. At that time, doctors feared she was developing a " lodge syndrome ", a serious condition characterized by excessive pressure inside a muscle.

Twelve days after the accident, the doctors decided to treat the woman with tecovirimat for 14 days, with a single dose of vaccinia immunoglobulin, which consists of an antibody from individuals already vaccinated against the disease. The woman also received antibiotics to prevent a bacterial infection of her wound.

According to the report, it was after 48 hours of treatment that his fever disappeared and the pain and swelling of his finger decreased. Nevertheless, areas of necrotic tissue (either dead) on her finger have not fully healed for more than three months, and she has not been able to get to work during this time.

When asked why she had not initially agreed to take the smallpox vaccine for prevention, the laboratory employee stated that at the time she "  did not understand the extent of the consequences that the 'infection could cause  '. In addition, the latter thought that it would be difficult to manage the lesion of the vaccination site and was worried about possible side effects (mentioned above).

Also according to the report, in this particular case, tecovirimal has been used safely to treat a vaccinia virus infection . However, "  as this is only one case, it is unclear whether the drug would be justified for other infections with this virus, " the authors said.


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