Virology Case Study - Answer
HISTORY
A 23 year-old male security guard working in a small department store was stabbed with a needle on a syringe of an intravenous drug addict he was arresting for shoplifting. Two months later he developed general malaise, with nausea and vomiting. He lost his appetite and began to lose weight. When he noticed darkening of the urine and a yellowish color to his sclerae, he came to your office. The patient denied a history of hepatitis or liver disease. He denied drug abuse, and had no history of blood transfusions, surgery or exposure to jaundiced individuals. He never traveled outside the US.PHYSICAL EXAMINATION
Physical examination revealed a well developed young man in no acute distress. Positive physical findings included: jaundice and a firm, enlarged and tender liver. He had no adenopathy.
Questions and answers:
1. The security guard developed hepatitis 2 months after the incident involving the hypodermic syringe
(a) given the length of time that has elapsed, is it likely that the incident has anything to do with the disease?
Since the incubation time for hepatitis A-E is from about 15 days to about 50, 160, 180, 64, 50 days, respectively, it is quite possible that the incident was relevant to the disease in the security guard.
(b) if the incident had occurred 48 hrs prior to onset of symptoms, would it be likely it had anything to do with the disease?
It would be unlikely, all of these viruses have a much longer incubation time (15 days or more).
2. If one were to acquire hepatitis via a needle stick from the syringe of an intravenous drug addict, what kind(s) of hepatitis would be most likely?
The most likely kinds for parenteral transmission would be hepatitis B, hepatitis C and possibly hepatitis D (which would require the presence of HBV).
Hepatitis A is usually transmitted via the fecal-oral route; there is a viremia with HAV but it is transient (a chronic carrier state does not develop) and although there have been cases of parenteral transmission, they are very rare; so it seems very unlikely that the guard would have gotten HAV from the needle stick.
3. Laboratory tests showed:
HAV Ab(total) Positive
HAV Ab(IgM) Positive
HBsAg Negative
total anti-HBcAg Negative
anti-HBsAg Positive
HCVAb(total) Negative
(a). How do you interpret the result of the HAV tests?
The security guard has antibodies to HAV and these include IgM antibodies, thus he has had a recent exposure to HAV (since he has IgM antibodies). It is possible that this result is because he has recently been infected with or vaccinated against HAV, further questioning of the guard should clarify this point.
(b). How do you intepret the result of the HBV tests?
Since he has no HBsAg the guard is not a chronic carrier. The guard has anti-HBsAg indicating that he has been either infected with HBV or exposed to the HBsAg present in the vaccine. Thus he has either recovered from HBV infection or he was vaccinated. Since he has no anti-HBcAg it seems probable that this is because he has been vaccinated (there is no HBcAg in the current vaccine). He should be immune to HBV. Again, further questioning of the guard should clarify this point.
(c). Is the security guard likely to be infectious for viral hepatitis?
Causes of viral hepatitis include hepatitis A-E, yellow fever, and it is sometimes seen in infections with Epstein Barr virus. It is possible that there could be more than one virus present. EBV is unlikely since there was no adenopathy (but could be confirmed by further tests). Yellow fever and HEV are unlikely since he had not been out of the country. From the serological data he appears not to have either acute or chronic HBV or HCV. (Because the appearance of anti-HCV may be delayed in patients with acute HCV infection, testing should be repeated if hepatitis C is suspected and initial testing is negative for anti-HCV: anti-HCV is detectable by 5-6 weeks after onset of hepatitis in 80% of patients and by 12 weeks in 90%). The guard is apparently suffering from HAV (by a process of elimination combined with the serology suggesting recent exposure to HAV). Since he has developed IgG antibodies, he is past the period of peak infectivity (furthermore, jaundice with HAV infections typically occurs when patients are past the peak of viral shedding) but there may still be some virus in the feces.
(d). Is he at risk for developing chronic viral hepatitis?
The known forms of chronic viral hepatitis are due to HBV (the guard has been vaccinated and has protective antibody), HCV (the serological results were negative, so he does not seem to have HCV but should be retested, if exposed in the future he has no protective antibodies, and there is no vaccine at the moment) and HDV (no risk if the guard has protective antibody against HBV). So the guard is probably not in imminent danger of developing chronic viral hepatitis (unless he turns out in a future test to have HCV) and is not currently a chronic carrier of viral hepatitis.
(e). Should he be tested for HDV?
Since he does not have HBV, he cannot be infected with HDV, so testing is unnecessary.
Note: since the guard most probably did not get the HAV from the needle stick, other sources of infection should be considered, such as via a child in the family, eating of raw seafood such as oysters, possibly eating of contaminated uncooked food etc.
Note: there are other causes of hepatitis, such as CMV, toxoplasmosis, leptospirosis, secondary syphilis, exposure to toxic chemicals (including alcohol), toxic drug reactions, etc. If the guard had been vaccinated recently against HAV, alternative explanations should be explored.
Comment: The risk of acquiring a blood borne viral infection from an infected individual via a needle stick varies widely from pathogen to pathogen, according to the pathogen, the degree of viremia, the details of the stick, etc. but very broadly speaking risk values are:
HBV in the order of 30%; HCV in the order of 3%; HIV in the order of 0.3%
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