HCV Survival in Syringes Affected by Syringe Type, Time and Temperature

Below is the transcript of a press conference held at CROI 2010 on Feb. 19, in which Elijah Paintsil, M.D., F.A.A.P., of Yale University School of Medicine in New Haven, Conn., discusses a study he presented on the survival of hepatitis C virus (HCV) in syringes. This press conference was moderated by David Thomas, M.D., of Johns Hopkins University.

Elijah Paintsil: We have been interested in looking at survival of hepatitis C virus in syringes.¹ As we've heard in the preamble, it is disproportionately affecting people who inject drugs. The virus is actually transmitted in the same mode, more or less, like HIV. But we also see that there is differential prevalence of HCV and HIV. Worldwide, it's about 30% to 95% of drug injectors infected with this virus. In the United States, where HIV in injection drug users is low, from about 1% to 10%, you still have hepatitis C prevalence of about 30% to 85%.

So we looked at it. These viruses are very similar. Why is one having a higher prevalence? We thought that it's probably due to the long period of survival. Now we're not able to answer this question, but we with others have been able to develop a lab model that allows us to really replicate this virus. We simulated injection drug use practices: load syringes, store them at different temperatures -- 4 degrees [Celsius], room temperature [i.e., 22 degrees Celsius] and [37 degrees Celsius] -- for up to 63 days and then look at how much virus would we recover.

Our main findings, which we think are really neat in terms of the fact that what we found could be really used in prevention messages and strategies: One, we found that the survival of the virus depends on the syringe type, i.e., the design and then the volume of the syringe. It also depended on time. And then also, lastly, it depended on temperature. So if you look at the syringe exchange programs, you can use any of these three to work. One, the type: Most programs give to the injection drug users syringes of their preference. And we found that syringes that have detachable needles could have these viruses survive for up to 63 days. The insulin syringes, which have an attached needle, we only were able to recover viruses up to seven days.

And then when you look at the other aspect of this, it's time. Most syringes now being used by injection drug [users] stay in circulation from zero to about 23.5 days. Interestingly, during that period, we also found that the virus that we recovered had very high titers, so the virus is very infectious during that. So we may have to make the effort to reduce the circulation time and then also be able to really take the used syringes out of the street.

Then also temperature: People inject in different geographical regions. We saw that at 4 degrees [Celsius], the viability of this virus is enhanced. So if you are in a cold place, something that we really have to study further to substantiate, but there is some suggestion to that effect. Thank you.

Reporter #1: Do you believe that the findings from your syringe study have implications for needle exchange programs? For instance, should they try to give out insulin syringes, as opposed to other types, even if that's not what people prefer?

Elijah Paintsil: Thank you for that question. Certainly, it has implications, because we now know that the longevity of the virus depends on the syringe type. And the insulin ones, the virus did not stay alive longer; so looking at that face value, it's probably expedient to give out insulin syringes than the syringes that are detachable. And again, volume probably matters. But I think the bottom line is not to use the reused syringes. I mean, that's the most important, because during the period we have most syringes stay in circulation from zero to 23.5 days. And we found that we could recover live viruses during that time, so the message is not to use the syringes.

Reporter #2: Could you just elaborate a little more on the question of temperature? And are you talking in degrees centigrade or Fahrenheit?

Elijah Paintsil: Thank you. The temperatures that we used were in centigrade. Four degrees, that is equivalent to the ordinary refrigerator. And then 22 degrees, it's equivalent to room temperature. And then the 37 [degrees], that's just the temperature of an incubator that we dialed up to 37 centigrade.

Reporter #2: And what happened to the virus at those temperatures?

Elijah Paintsil: What we saw was that the longevity or survival was generally inversely proportional to the temperature, so that 4 degrees [Celsius], they survive longer than at 22 [degrees Celsius] and then 37 [degrees Celsius].

Reporter #3: Are there implications as well about possible reservoirs in hospital reuse of the devices that have the syringes? We've seen a problem with some pathogen transmission in hospitals, other pathogens. And I'm wondering if we might see it here also. Could this be a way of transmitting HIV or HCV, either one?

Elijah Paintsil: Thanks, so the question is about other things -- like bench top, or other vials or injection bottles -- that are used in the hospitals. The problem as it now is is that we are not able to cultivate viruses from human beings in the lab. So what we used was a lab strain. And we have not done the studies to stimulate all these other conditions. But we, going forward, could try to replicate what happens in health care settings if you put virus in injection vials, or IV [intravenous] fluid bags or even a wet surface. What are we going to see? We don't know that yet.

Reporter #4: Given your findings of a lower persistence of the virus in different conditions, is there any way to tell how many fewer possible infections could result from someone switching the type of needle that's offered at these programs or from lower temperature versus higher temperature settings? How much impact is this likely to make on disease if taken into account in these programs?

Elijah Paintsil: Thank you for that question. I think ours is just but the first step of highlighting these conditions that we saw. Going forward, I think we could actually do epidemiological studies where injection drug users who are HCV [infected], I can figure out people asking them questions about their injection practices: Where do they store their syringes? How long do they keep their syringes? So those would be sort of follow-up studies. We cannot definitely comment or say much on that. But I can see people taking this up and then doing epidemiological studies and informing us. Certainly, if they do, those could be used also as prevention messages and strategies.

Reporter #2: To pursue even more speculation, if the virus does not seem to survive at high temperatures, has anyone noticed that there are waves of hepatitis C infection during the winter as opposed to during the summer? I just wonder if there's a temperature gradient to disease exposure.

Elijah Paintsil: Thank you very much for that question and I just like the way you preface that as speculative. We're also in that. We are excited also to look at that. Hepatitis C belongs to a family of virus we call the flavivirus, usually these are in birds. And generally people think that birds have a higher core temperature than human beings. It's difficult at this point. I think we need more studies and really finding out. Our study highlights situations where people can now go back and see the incidence of hepatitis C in different seasons. So this is really something that probably in the future we'd have more data on.

Reporter #4: Dr. Thomas, do you have any comment on the things that we've been asking here?

David Thomas: No, I think that I agree with those statements that this is just the beginning of trying to understand, having some science to help us reduce the risk of transmission of hepatitis C by drug use, all different ways that that could occur. We know that needle exchange is sufficient to reduce HIV transmission. It's been harder to establish the science to inform public health policy for hepatitis C transmission. I think these guys are right on track with their method for doing that. And they're going to be, in the next six to 12 months, teaching us more about all the other things that drug users share besides just the syringe. I mean it could be the cookers and the cotton and all the other parts of the drug-use implements that are critical. It's kind of like if you're lighting off a firecracker, taking a step back may be all you need to do to protect yourself. If you're lighting off a grenade, you might need to get further back. Hepatitis C is more transmissible than HIV by needle stick. It's a lot more transmissible. And so we need to have work like what they're doing to sort some of that out.

Robert Heimer: I worked with Elijah on this study. I'm Robert Heimer from Yale School of Medicine. Yesterday afternoon, I went out to the Homeless Youth Alliance out in the Haight [in San Francisco, Calif.], where they do needle exchange. I saw the needles that they have on the walls there, including syringes with detachable needles. The reason they give them away to drug users is some drug users inject substances that require larger bore needles, especially people who are injecting hormones. And I asked -- the director had heard about our work and said, "Look, we have to do that." So we both agreed: The answer for situations like that is you just have to give out more syringes so that people only use their syringe once. Now that the federal ban on funding for syringe exchanges has been lifted, it would be nice to get more money so that people have more money to give out more syringes to the people who need them.

This transcript has been lightly edited for clarity.

Reference

1. Paintsil E, He H, Peters C, Lindenbach B, Heimer R. Survival of HCV in syringes: implication for HCV transmission among injection drug users. In: Program and abstracts of the 17th Conference on Retroviruses and Opportunistic Infections; February 16-19, 2010; San Francisco, Calif. Abstract 168.

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