Chickenpox
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[edit] Chickenpox
Chickenpox is one of the six childhood rashes and is very common in childhood, but can also affect adults. As already stated under the chapter on shingles, the same varicella-zoster virus that causes shingles in older children and adults causes chickenpox in younger non immunized children. Scientifically this virus belongs into the herpes family of viruses and is called "human herpes virus, type3". For the first 6 months a newborn is often immune against chickenpox because of the transferred antibodies from mother with breast feeding. Children tend to get chickenpox as a less severe illness than teenagers or adults do.
Signs and symptoms: There is an incubation time of 10 to 14 days after exposure before the typical skin rash occurs. One to 1 1/2 days before the skin rash appears, the patient has a headache, mild fever, and generally feels unwell. This is more pronounced in children older than 10 years and in adults. The typical skin rash starts in the face and on the trunk with initial disc like macules that erupt in the center with a characteristic teardrop vesicle. These beak down within a few hours, partially because they are very itchy and are scratched open by the patient. They tend to get infected by bacteria and it is very important to treat these infected lesions with antibiotics as it is the bacterial superinfection, left untreated, which leaves the patient eventually with a scar. In the past there was an attitude that this would be a harmless childhood rash and benign neglect would be the right approach. This attitude has changed radically as will be explained below under treatment of chickenpox. Epidemics of chickenpox used to happen every 3 or 4 years before widespread vaccination has been implicated. These epidemics still occur in non vaccinated children; unfortunately many jurisdictions still consider chickenpox as not being part of the routine vaccination program and the parents often shy the expense of the vaccine.
Complications of chickenpox: When the scratched open,infected skin lesions are superinfected with streptococcal or staphylococcal bacteria cellulitis can develop and in rare occasions even toxic shock syndrome (due to staphylococci). Pneumonia is not infrequently found in adults who get a more severe course of chickenpox or in immunocompromised children. Other complications are myocarditis or hepatitis. In less than 1 in 100 patients an encephalopathy can occur (changes in the brain function), which fortunately is mostly reversible within a few weeks. However, another neurological complication, called acute postinfectious cerebellar ataxia, occurs occasionally at the end of the disease when all the other symptoms including the rash disappear. Around that time other rare complications like palsies of cranial nerves, a myelitis and a multiple sclerosis like illness can develop. Reye's syndrome can develop in children 3 to 8 days after the skin rash started. The use of aspirin in the febrile stage in the beginning can be a triggering factor. It is better to use acetaminophen for a fever to prevent this complication.
Diagnosis: The diagnosis is usually made because of the typical rash with initially red macules (red round dots) that develop teardrop vesicles in the center of these within a few hours. These often break down so that there is a red macule with a central ulceration that often gets superinfected. The lesions are very itchy and are present even in the mouth cavity, around the edges of the eye lids, in the respiratory tract, even in the rectum and in the vagina. The physician will be able to diagnose chickenpox with such a precision that blood tests are rarely indicated. Sometimes there are more difficult cases in patients who are immunocompromised such as patients with AIDS, immune suppressed patients with cancer, due to malnutrition etc.). Here is an example of a newborn whose mother contracted chickenpox late into the pregnancy. As the skin rash is very atypical, some blood tests would be in order to diagnose this atypical chickenpox rash, so that appropriate treatment can be given. A sample from the skin lesion is taken with a glass slide and the technician can use an immunofluorescent test in the laboratory to document the presence of type3 human herpes virus. Other chickenpox diagnostic tests that can be done by a virology lab are viral cell cultures from scrapings or the demonstration of a rising serum titer levels regarding the chickenpox virus. In some centers electron microscopic diagnosis is available.
Treatment: Many cases of chickenpox can be just treated observantly. However, after a few days of scratching many patients get superinfection of the open lesions (partially with own skin flora, partially with pathogens as mentioned above). The physician may decide to treat this with a short course of antibiotics. Colloidal oatmeal baths can help reduce the itch. Calamine lotion topically will also help reduce the itch and scratching. There is a risk of overusing antihistamines systemically and locally as this may cause encephalopathy (damage to the brain). Simple measures help such as keeping the nails cut short, having daily baths with soap and water to reduce skin colonization with bacteria. Antiviral antibiotics such as famciclovir (=Famvir), acyclovir (=Zovirax) and valacyclovir (=Valtrex)are reserved for the more severe cases and for immunosuppressed patients. In order to have an influence on reducing the severity and the length of the course of chickenpox the antiviral medication has to be taken within 24 hours of the onset of the rash. In children where the course of the disease is usually lighter the antiviral antibiotic is not used, but superinfected skin lesions may sway the doctor to prescribe a regular antibiotic.
Prevention: Chickenpox vaccination has made a big difference already and will have an even more positive impact on society as more people use it for prevention. Here is a Canadian web site that explains the chickenpox vaccine. And here is the CDC web site about the varicella (chickenpox) vaccine. The target groups who should definitely be vaccinated are women of child bearing age (to protect the fetus and the newborn) and people with chronic illnesses (they would with exposure to it get severe chickenpox). However, the physician will say that vaccination is not permissible for any person with an acute illness, patients with a weakened immune system like patients suffering from AIDS or cancer. In addition pregnant women, children on salicylates and patients on high doses of corticosteroids for asthma or other illnesses could also not take the chickenpox vaccine. After exposure to chickenpox the disease outbreak can be prevented with an intramuscular injection of varicella-zoster immune globulin. However, due to shortages of this there are restrictions of who will qualify to getting this. This link describes this in more detail.
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References: 1. David Heymann, MD, editor: Control of Communicable Diseases Manual, American Public Health Association, 2004. 2. The Merck Manual,18th edition. Merck&Co., 2006.
