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Intrauterine Transmission - CDC Press Briefing Dec 19, 2002 & NYTimes Article
Date:
Dec 20, 2002
Posted by:
Lois Levitan (lcl3@cornell.edu)
[Notes from WestNileVirus-L Moderator:
a. "Intrauterine Transmission" is the term used by CDC to describe
what was previously called "Transplacental Transmission" in the
subject line of postings to this listserv. WestNileVirus-L will
heretofore use the CDC terminology.
b. This posting contains an edited version of the transcript from
the CDC Dec 19 2002 Press Briefing, during which the the Dec 20 MMWR
articles re: WNV are discussed, following Q&A about CDC smallpox
preparedness. Nothing of substance was deleted in the editing
process. Many very interesting points are explained and clarified.
The full transcript is online at
http://www.cdc.gov/od/oc/media/transcripts/t021219.htm. Press are
told to call CDC press office at (404) 639-3286 with follow-up
questions or for additional information.
c. This posting also contains a related article by Lawrence K. Altman
in the Dec 20 NYTimes, "Transmission of West Nile in the Womb Is
Confirmed" (http://www.nytimes.com/2002/12/20/health/20NILE.html).
This article went to additional sources and contains some information
not in the CDC transcript.]
------------------------------------------------------------------ DECEMBER 19, 2002 CDC PRESS BRIEFING [edited] ------------------------------------------------------------------
CDC MODERATOR: Drs. Lyle Petersen and Dan O'Leary are our West Nile virus experts out in our division of Vector-Borne Infectious Diseases in Ft. Collin, Colorado. [Dr. Petersen is Deputy Director for Science of the Division of Vector-Borne Infectious Diseases and Daniel R. O'Leary, DVM, is a medical epidemiologist with the Arboviral Diseases Branch, the Division of Vector-Borne Infectious Diseases.]
DR. PETERSEN: Dr. O'Leary will give remarks about the surveillance article and the transuterine infection article, and I will follow up with a brief statement about the occupational risk article.
PROVISIONAL SURVEILLANCE SUMMARY FOR WEST NILE VIRUS IN 2002
DR. O'LEARY: I'll start off with a brief summary of the provisional surveillance for West Nile Virus in 2002 in the United States. Between January 1st and November 30th of 2002, West Nile Virus activity was reported to the CDC from 44 states and the District of Columbia. It spread for the third consecutive year into new areas of the US as far west as Washington State. In 2002, there were nearly 3,400 human West Nile Virus illness cases, reported from 37 states and D.C. And over 2,300 of these cases were infections of the central nervous system, otherwise termed "West Nile meningoencephalitis." These cases represented the largest epidemic of meningoencephalitis caused by West Nile ever documented.
In addition to meningoencephalitis cases, there were over 700 cases of West Nile fever, a milder form of West Nile infection, that affects relatively younger age groups. The states that reported the most human West Nile Virus cases were Illinois, Michigan, Ohio, Louisiana, Indiana, and Texas. The first human cases in the southern states proceeded those in northern states by about one month. While persons at any age can develop neurologic disease from West Nile infection,persons in older age groups are at higher risk for West Nile meningoencephalitis and death.
In 2002 we also reported person-to-person West Nile Virus transmission by blood transfusion, organ transplantation, intrauterine transmission, and possibly by breast feeding. In 2002, numbers of reported West Nile cases in animals were unprecedented. There were over 14,000 reports of West Nile infected dead birds from 42 states and D.C., and over 9,000 reported equine cases, representing a twelve-fold increase over 2001 from 38 states. Bird and horse-based West Nile surveillance continued to be the mainstay for monitoring the activity of the virus and its spread in the United States.
Also the capture and testing of mosquitoes for West Nile infection is an augmentative mainstay for the state level surveillance programs.
That concludes my summary on the West Nile surveillance. And what I'd like to do now is move on to the article that was published on intrauterine West Nile infection.
INTRAUTERINE WEST NILE VIRUS INFECTION
The Onondaga County New York Health Department, the New York State Department of Health, and the CDC present in this week's MMWR the first report of intrauterine West Nile virus infection. West Nile Virus has not previously been associated with infection of the fetus or adverse birth outcomes. In 2002 a pregnant woman developed West Nile Virus infection and she gave birth after a full-term pregnancy to an infant who was diagnosed with brain abnormalities. Laboratory tests confirmed the infant's recent infection was West Nile Virus.
Intrauterine infections with other mosquito-borne viruses related to West Nile have been associated with miscarriage or severe illness in infants, but the frequency of these adverse events is unknown. This single case that we report does not prove that West Nile Virus infection causes adverse birth outcomes. Pregnant women should take precautions to reduce their risk for West Nile Virus and other mosquito-borne viruses by avoiding mosquitoes when possible, using protective clothing and repellents containing DEET, per manufacturer's directions. There is currently no effective treatment for West Nile Virus infection.
Pregnant women living in areas of current West Nile Virus activity, who develop illness with fever should seek professional health care, and if it's deemed appropriate, they should be tested for West Nile infection. However, pregnant women without illness should not be screened for West Nile infection.
That concludes my summary of these two articles. Thank you. And I'll hand it to Dr. Petersen.
LABORATORY-ACQUIRED WNV INFECTIONS IN THE US
DR. PETERSEN: We report two recent laboratory-acquired West Nile Virus infections in the United States. West Nile Virus infection in two microbiologists resulted from exposure through percutaneous inoculation in laboratories. One was from a needle stick exposure to a person handling live virus, and the other person was a person who received a scalpel injury while handling a West Nile-infected dead bird.
Illnesses in both laboratory workers were mild and self-limited, which is typical of illnesses in West Nile virus infected persons. These cases confirm that laboratory workers are at risk for occupationally-acquired West Nile virus infection, including West Nile virus meningoencephalitis. Employers and workers should follow procedures to minimize the risk of injuries from sharp instruments and to minimize airborne exposures. Workers should clean and treat wounds immediately and thoroughly, if they occur, and should report any injuries to supervisors for further monitoring. Employers should report any cases of infection to public health authorities. That concludes my statement.
QUESTIONS
QUESTION A--Dietra Henderson with the Denver Post:
[Question 1] re: the interuterine West Nile virus infection. The mother's age is twenty years old, and she is described as previously healthy. Would you expect such severe illness in that case or does pregnancy or the herpes add another layer of risk for her?
[Question 2] I'm trying to get a sense of the significance of the congenital abnormalities for the infant. It's hard for me to tell from the description exactly what's going on with the infant. Is the infant still alive?
[Response 1] DR. O'LEARY: As stated in the WNV summary article, increasing age is a risk factor for more severe West Nile viral disease. However, we have documented meningoencephalitis or central nervous system illness in younger age groups as well, and although it happens less frequently than in older age groups, it is not unheard of, that this young woman developed a central nervous infection of West Nile virus. I don't want to speculate on whether her pregnancy was a risk factor for additional severity of illness, and if Dr. Petersen wants to comment, that's fine. But I don't want to speculate. We don't know if pregnancy is an additional risk factor for severity of West Nile illness.
[Response 2] DR. O'LEARY: Yes. The infant is still alive. The infant did have extensive pathology, pathologic changes to its brain that were revealed on magnetic resonance imaging, or MRI, and its development is being monitored by its doctor, and--but yes, the infant is still alive and is getting regular checkups.
-----
QUESTION B--Rita Rubin with USA Today:
[Question 1] Are there other possible explanations for the problems the baby was born with? I mean, are these a typical combination of problems?
[Question 2] I also wondered, is the baby blind, because I know there was a problem with the baby's eyes at birth.
[Question 3] Is it possible that there have been many more cases of interuterine transmission from women who did not get sick and still could have passed it on to their newborns?
[Response 1] DR. O'LEARY: As far as your first question, addressing other explanations for the baby's neurologic illness, other high-suspect infectious agents were ruled out as the cause of the baby's abnormalities. There are certainly birth defects that occur for reasons that are unknown and other high suspects have been ruled out in this case. The woman's history doesn't indicate risk factors for any other type of abnormalities, toxicologic, those sorts of things. Other infectious agents were ruled out. She was otherwise healthy and there's nothing in her history that would raise a red flag as far as a risk factor for the baby's problems.
[Response 2] The baby did have chorioretinitis at birth. I do not know if the baby is blind at this time.
[Response 3] As far as reports of illness from asymptomatic, in babies born to asymptomatic women, that is very difficult to assess because the cases reported to us are cases of West Nile viral illness, and asymptomatic women often do not know that they were infected during pregnancy. So, right now, we wouldn't have a way of assessing that.
QUESTION: Well, some just say it could be a more common problem than recognized because if these are--you know, there could be women transmitting infection who themselves did not have any signs of illness.
DR. PETERSEN: I'd like to just comment on the explanation of the baby's neurological deficits. It's very possible that West Nile virus was the cause of this baby's neurological deficit, but with only one case it's impossible to really determine cause and effect. Other known causes of similar neurological deficits were ruled out.
As far as other cases of interuterine infection, your comment that many of the women infected with West Nile virus may have transmitted the infection of their baby and not even known it because the baby may not have any symptoms is a very good comment. With the hundreds of thousands of people infected this year, many pregnant women were undoubtedly exposed to the viru. The fact that we haven't seen a great deal of suspect cases is fairly reassuring. As far as other cases of interuterine infection, we do have one well-documented case that we have followed, where the woman clearly became infected during her pregnancy and delivered a healthy infant, and it was shown that the infant had not been exposed to the virus.
QUESTION: And that that women got sick and that's why you knew she was infected.
DR. PETERSEN: Correct.
-----
QUESTION C--Larry Altman with the New York Times:
[Question 1] It's not clear from the report why the doctors suspected abnormalities in the baby, because as I read it, it said the initial neurological examination was normal.
[Question 2] What would it take to prove cause and effect?
[Question 3] What is the risk of DEET to mothers who would take it, and what if this mother had used DEET and then had the baby with the abnormality? How would we be assessing it?
[Question 4] What other viral infections can be transmitted in utero besides Japanese B and dengue? What I'm trying to get at is how unusual or how usual is adding the possibility of West Nile to the list? I mean, is it a small list? Of viruses that are known, is it a small percentage or a large percentage?
[Response1] DR. O'LEARY: The doctor suspected abnormalities in the child on a general physical examination after birth. The doctor was doing an examination of the child's eyes and noticed, was having a hard time doing a complete assessment of the back of the child's eyes with an ophthalmic exam, and so ordered a consult, and an ophthalmologist was called in, completed an ophthalmologic exam and documented some abnormalities in the child's retinas, which led to an expanded neurologic exam that revealed the brain abnormalities.
[Response 2] about proving cause and effect in interuterine infection, in the cases documented with interuterine infection of Japanese encephalitis and dengue, the virus was actually cultured from either blood or blood of live-born children or aborted fetuses, and in this case we would consider confirmation of--we would consider a culture of the virus from tissues from the baby, actually the baby's central nervous system, confirmation that there was infection, and many times, what is required for further proof of actual causality, virus causing the pathology, is to look at biopsy tissue, and in this case of course it was unavailable. You can see pathology in biopsy tissue slides.
DR. PETERSEN: The other thing is that if we started to see certain types of congenital abnormalities that were more likely to occur in women who were exposed to the virus during their pregnancy versus women who were uninfected, that would also provide evidence that there was some cause and effect of the infection with the virus to certain congenital abnormalities.
[Response 3 re: The use of DEET in pregnant women.] DR. O'LEARY: We know of no contradictions to the use of DEET in pregnant women. There's no evidence that using DEET during pregnancy causes problems for either the mother or the infant.
[Response 4] re: What other viral infections can be transmitted in utero: DR. O'LEARY: There are other viral infections such as rubella virus, herpes virus, and [others] that I know are transmitted in utero. I do not have in my recall right now a comprehensive list of viruses that are transmitted in utero, so I can't answer that question very accurately at this point.
QUESTION: Can we get an answer afterwards?
CDC MODERATOR: Yes, Larry, just call the Press Office, and we'll try to square you away?
DR. PETERSEN: As you know, a number of viruses all can be transmitted, and it includes CMV, lymphocytic choriomeningitis virus, EBV. Others could be transmitted that way. What the whole long list is we could supply you later, but it is quite a long list.
-----
QUESTION D--Rick Weiss with the Washington Post:
[Question 1] You've got evidence so far of antibodies in the child, but not good evidence yet of infection, and I'm wondering if there's any feeling on your part that antibodies themselves can cause the kind of problems that you're looking at here, and, if so, what are the implications for that with vaccination, potential vaccination if such a vaccine were to be developed for pregnant women? That is, if antibodies to West Nile might have an effect on the developing central nervous system.
[Question 2] To the extent that other viruses have been shown to cause problems in fetuses or newborns, have any of those complications been similar pathologically to the evidence of brain problems that you're seeing here or is this different?
[Question 3] I still don't have a sense of the clinical condition of the child [vis-a-vis] behavior and development right now. To a lay reader like myself, I read about major changes in white matter in the brain, and I think the kid is pretty messed up, but can you please describe the condition.
[Response 1] DR. PETERSEN: Going to your first question about the evidence of antibodies in the child, we have no evidence that the presence of any West Nile Virus antibodies would have any adverse effect on the infant. What is important is, is that IGM antibody was detected in the infant, and IGM antibody is not transmitted from mother to child, so the presence of IGM antibody in the child indicates that the child was actually infected with the virus.
[Response 2] Whether other viruses caused similar complications or whether they're different from what we've seen here, I am not a pediatrician, actually, and so I'd be happy to answer that question off-line when we can get you a better answer. Some of the abnormalities associated with this child could be consistent with other viruses that have been ruled out, but I would like to defer that till later.
[Response 3] As far as the clinical condition of the child, the child does have severe neurological abnormalities, and further information can be obtained from the Onondaga County Health Department.
QUESTION: Is there anything at all you can say with regard to behavior? I mean, what does it mean to have severe neurological abnormalities. You're not talking simply about an MRI image. You're talking about the way the child behaves?
DR. PETERSEN: Correct, and we do not have the details of the child's exact clinical condition at this moment. However, the Onondaga County Health Department has access to that information.
QUESTION: I just have to say, if I can try one more time, I'm not optimistic about the Onondaga County Health Department, even though it's my home county, is going to tell me a lot about this.
[Laughter.]
QUESTION: But, certainly, you could at least narrow it down to, you know, motor versus cognitive or both, something like this?
DR. PETERSEN: If I had the details, I could tell you, but we do not have the details of what you're looking for. Another source you could contact would be the New York State Health Department.
-----
QUESTION E--John Lauerman with Bloomberg News: To the best of your knowledge, is this the first such case in the world or just in the US? Is it possible or likely that this has happened elsewhere?
DR. O'LEARY: We've done a literature search, and this is the first documentation of this type of infection that we've seen reported anywhere.
-----
QUESTION F--Alison McCook with Reuters Health:
[Question 1] I was wondering if you had, if anyone had suspected before that West Nile Virus could have been transmitted from mother to child, and if you hadn't, why not?
[Question 2] And now that you know it may be, does this give you any clues as to how the virus works in the body, any clues that might help come up with treatments or anything in the future?
[Response 1] DR. O'LEARY: I think that this is a case of hindsight is 20/20. We, in looking back through the literature, we can see that there are other related viruses that have caused abnormalities in young infants... We were looking for these cases after the breast-milk incidents. We have been doing surveillance for these abnormalities in pregnancy, but we hadn't a precedent to compare against, and so--
DR. PETERSEN: Because congenital infection has occurred with other related Flaviviruses, we had put out the word to state health departments to report any cases such as this to us, and this is how, through that kind of informal surveillance system, this case was reported.
[Response 2 re: clues as to how the virus behaves in the body] DR. PETERSEN: Well, the one clue it does give you is that the virus can be transmitted in utero, which hadn't been documented previously.
-----
QUESTION G--Lynne Boyle [ph], with WebMD
[Question 1] I wanted to make sure I understand correctly [that] there has been one other documented case of West Nile Virus in a pregnant woman or more than one, and there was no transmission there?
[Response 1] DR. O'LEARY: That's correct. We've had one documented case that has come to term, and the baby was born. We know of a couple of other cases where pregnant women have not had their children yet.
[Question 2] Can you elaborate on what is known or suspected about transmission from breast milk?
[Response 2] DR. PETERSEN: All we know about the breast-milk transmission is that we have had one fairly well-documented transmission, although not completely conclusively proven. This was a case of a woman who received a couple of transfusions immediately postpartum. One of those transfusions was subsequently shown to be infected with the West Nile Virus. The woman became ill with West Nile Virus several days later, and was actively breast feeding before and during part of her illness.
We measured IGM antibodies in the baby, which were positive, which suggested that the baby had been infected. IGM antibodies are not transmitted from mother to child, so we know for a fact that the baby had actually become infected. We were also able to show viral genetic material in the breast milk of that woman. Now we have another case that's a very similar case of a woman who got infected from a blood transfusion immediately postpartum who did breast feed her baby, and that baby did not become infected.
-----
QUESTION H--Jim Erickson with the Rocky Mountain News:
[Question 1] Dr. Petersen, you said you don't have details on that infant's case, but in the MMWR article, where it says "severe cerebral abnormalities, including severe bilateral white-matter loss in the temporal and occipital lobes, and cystic change in one temporal lobe consistent with focal cerebral destruction," can you just explain, in simple terms, what that is, what that means?
[Question 2] Are you allowed, can you tell me a DOB and sex on this infant?
[Question 3] We had a case out here in Denver where a woman who tested positive for West Nile claimed she got it by having intercourse with her husband, who was also positive for West Nile. Does this case with the infant lend any credence or say anything at all about the possibility of getting West Nile through sexual intercourse?
[Response 1] DR. PETERSEN: As far as the neuro imaging results that we've presented here, in lay terms what it means is that, for some reason, the infant has had destruction of part of its brain, for whatever cause. One cause would be West Nile Virus infection. And whenever you have this degree of destruction of the brain cells, it would be expected that there would be some cognitive and other neurological abnormalities associated with that.
[Response 2] As far as the date of birth and sex of the infant, we are not releasing that information for patient confidentiality reasons.
[Response 3] Now to your question for what does this mean for sexual intercourse, you can't draw any conclusions between the case in Denver and the trans-uterine transmission. We know that this is a blood-borne virus, and as a blood-borne virus, we knew that there was a potential for transmission in utero. As far as sexual intercourse, the case that was presented in Colorado was extremely inconclusive that sexual intercourse was the mode of transmission of that case. Although sexual intercourse could potentially be a mode of transmission, there's no evidence that suggests that it is at this point in time.
-----
QUESTION I--Larry Altman with the New York Times: Regarding the laboratory cases, you have in there that laboratory workers need to be trained in precautions, and you're saying there's a lot more lab work going on, suggesting there are a lot more lab workers involved now. Were the two who were involved here given specific training in precautions for this or does this suggest a lapse in training?
DR. PETERSEN: I cannot speak for the training of one of the cases. For one of the cases, the person was a very experienced microbiologist who has decades of experience in handling these types of viruses and is well trained.
-----
QUESTION J--Michelle Meyer with AARP Bulletin:
[Question 1 re: age and condition of fatalities]
[Response 1] Two people died who were reported to have had a milder form of the disease called West Nile Fever, both were persons over 80 years old.
[Question 2] Agewise, how about the other people; what percentage were over 50, what percentage were over 70? Do you have age statistics?
[Response 2] DR. O'LEARY: I don't have the percentage of the total in each age group, but I can tell you that the percentage of people with meningoencephalitis who died increases with age. For instance, 13% of people between 70 and 79 years old with meningoencephalitis died of their illness; 25% of people between 80 and 89, who developed meningoencephalitis died; 27% of people 90 to 99 with meningoencephalitis died.
[Question 3] What about under age 50 versus over age 50?
[Response 3] DR. O'LEARY: I would have to total those up for you. [Data per decile:] Of patients with meningoencephalitis--the central nervous system form of the infection--from ages 0 to 9, there were 0-percent fatalities; ages 10 to 19, 0-percent fatalities; ages 20 to 29, 1.5 percent died; 30 to 39, 0.8 percent died; 40 to 49, 1.7 percent died; 50 to 59, 3 percent died; 60 to 69, 9 percent died
-----
QUESTION L--Rick Weiss with the Washington Post: Comparing the two cases now that you've tracked of infection in pregnancy, one in which there appears to have been infection in the child and one in which no infection was documented, were there differences in the degree or extent or type of infection in the mother in terms of CNS involvement or anything like that?
DR. O'LEARY: No, both pregnant women were infected in the third trimester of pregnancy. Both pregnant women had evidence of West Nile infection in their central nervous system based on the presence of IGM antibodies. So they both had West Nile meningoencephalitis.
-----
QUESTION M--Dietra Henderson with the Denver Pos:
Question about the lab workers. In the case of the microbiologist with the extensive experience, it doesn't sound as though having been exposed to Japanese encephalitis or yellow fever incurred any protection against West Nile but it may have reduced the severity of the infection. Have you worked in animal models that actually underscore that result? I mean, have you infected birds or mammals with one of the other flaviviruses and then gone on to reinfect them with West Nile?
DR. : Yes. There is some evidence that what we call a heterologous antibody or infection with one virus may have some partial protection against another related virus, or another related flavivirus. There is some evidence that there is some protection, although this protection is not certainly, as was shown in this case, would not be of the degree that it would completely prevent infection.
For example, if you look at dengue viruses, there's actually four dengue viruses, and you can be infected with one of the viruses and then, you know, shortly thereafter, become infected with another one. So there is some cross-protection but it's not complete.
---
QUESTION N--Lanny Peterson with the Savannah Morning News: This is a question about the quarantined blood that was taken off shelves in the last week because of West Nile virus, and I'm wondering why the quarantine was limited. Apparently West Nile virus is endemic in in Chatham County around Savannah, and it's endemic in Georgia, and so I'm wondering why all products were not asked to be taken off the shelves?
DR. PETERSEN: The recommendations by the blood collection agency were state specific, they were not county specific, and recommendations were made to take plasma off the shelves during certain time periods when we know that West Nile virus was epidemic in [the state]. Now why there still may be plasma on the shelf in certain places and not others is largely due to issues of supply. The blood collection agency had recommended that products that were collected from donors during the peak period of transmission are removed first, and replaced first, until all the products during the epidemic period have been removed.
[Follow-Up Question] Do you know how many cases of transmission from transfusions of West Nile virus you actually have? And [since] we have Culex mosquitoes biting people right now, and infected birds dying here right now. why is the blood here collected safe?
[Response to Follow-Up Question] DR. PETERSEN: We have reported to on 13 cases of transfusion-related infection. There are approximately twenty more cases under active investigation and we fully expect to have more transfusion-related cases identified in the coming weeks. Now the salient question was why are blood products still being collected in Florida, given the fact that some transmission is occurring right now.
The reason is because it's all a matter of supply and need, and right now, as always, there is a large need for blood products in any given area, and the supplies are fairly limited. So it would not be practical to stop blood collection in places where some transmission may be occurring. More harm would be done than good.
Right now, in Chatham County, Georgia, although cases have been reported late in the season, the number of cases is rather small. I think my comments pertain to the entire southern United States where transmission could be occurring late in the season, and it would not be practical to stop blood collection in places where one or two cases may have occurred.
Just the fact that a very small number of West Nile virus cases are occurring at this time of the year indicates that really very few people are getting infected and the risk, while there would be some risk, the risk would be extremely small, and thus stopping the blood collection in those areas would probably produce more harm than good.
[Follow-Up Question 2] Do you think we should be warning people about to have surgery, that maybe they don't want to have a transfusion from somebody else's blood?
[Response to Follow-Up Question 2] DR. PETERSEN: The bottom line is that people who need to get blood products need them, and the benefits of giving those blood products is going to be much greater than any potential risk of getting West Nile virus infection, even at the height of the epidemic. What is being done now is an extraordinary safety precaution. The blood supply has never been massively contaminated.
The number of transfusion cases remains rather small, despite the fact that we've had a very large epidemic. But the blood collection agencies and the Food and Drug Administration and CDC want to be extra cautious and that's why these measures are being taken. So if you need blood products, West Nile virus should be very low on your list of concerns.
-------------------------------------------------------------------------------------------- New York Times -- December 20, 2002 TRANSMISSION OF WEST NILE IN THE WOMB IS CONFIRMED By LAWRENCE K. ALTMAN --------------------------------------------------------------------------------------------
A baby girl born infected with the West Nile virus in Syracuse a month ago is the world's first documented case in which the virus was transmitted in the womb, health officials said yesterday.
The baby was born with severe brain defects and is being treated for a respiratory infection in a hospital, said Dr. Lloyd F. Novick, the Commissioner of the Onondaga County Health Department in Syracuse. West Nile infection was diagnosed in the baby's 20-year-old mother before the baby was born.
Dr. Novick and federal health officials emphasized that they could document the baby's infection with the virus but could not prove that it caused her brain damage.
"It's very possible that West Nile virus was the cause of the baby's neurological deficit, but with only one case it's impossible to really determine cause and effect," Dr. Lyle Petersen, a West Nile expert at the Centers for Disease Control and Prevention, said at a news conference.
To reduce the risk of infection by the mosquito-borne virus, Dr. Petersen and other health officials urged pregnant women to wear protective clothing and to use insect repellents containing Deet in the mosquito season. The virus is still being transmitted in some Southern states.
"There is no evidence that Deet causes problems for a mother or infant," Dr. Petersen said.
The disease control agency said it did not advise doctors to use blood tests to screen pregnant women for West Nile virus, in part because no specific treatment exists for it.
The mother-to-child transmission was another surprising development involving the virus, which was detected in the Western Hemisphere for the first time in New York City in 1999.
Since then, epidemiologists have documented transmission of the West Nile virus through blood transfusions, to recipients of transplanted organs, possibly through breast milk, and to laboratory workers.
Also, birds have spread the virus quickly and widely throughout the country. The virus was identified in 2,289 counties in 44 states and the District of Columbia this year and for the first time in 1,929 counties and 16 states, officials at the disease control agency said. In 2002, the virus was identified in 359 counties in 27 states and the District of Columbia. [WestNileVirus-L moderator's note: Error, in 2001 the virus was identified in 27 states]
This year, the virus is known to have infected 3,389 people, of whom 2,354, or 69 percent, had inflammation of the brain or meningeal covering of the brain. There have been 232 fatalities, all but 2 in people who had neurological infections.
In August, the baby's mother suddenly developed a fever of 102.7 degrees, headaches, blurred vision, vomiting and abdominal and back pain. The fever resolved four days after she entered a hospital, but she then developed weakness in her legs. The mother, whose identity was not disclosed, left the hospital on Sept. 14 against medical advice.
Two days later she fell and returned to a hospital where West Nile infection was eventually diagnosed.
For that reason, doctors performed blood tests for West Nile virus on her baby after she was born in mid-November.
Because an eye examination showed an abnormality, doctors also performed magnetic resonance imaging that showed severe brain abnormalities, particularly in the occipital and temporal lobes that affect sight and hearing.
Scientists have documented intrauterine infection from a number of viruses, including chicken pox, H.I.V. and German measles, and two - Japanese B and dengue viruses - that are closely related to West Nile.
To learn more about the possible congenital complications of West Nile virus being transmitted in pregnancy, the disease control agency is starting a voluntary registry to monitor births among infected women.
The epidemic has required more scientists to work with West Nile virus in the laboratory, and the agency said recent accidental infections of two laboratory workers illustrated the need for training to help prevent additional such cases.
One laboratory worker became infected from a scalpel wound inflicted while examining a dead blue jay. A second laboratory worker became infected through a needle-stick injury while working with mouse brains.
Sometimes infection with one closely related virus protects against another virus. For example, vaccinia virus is used to prevent smallpox, which is caused by variola virus.
In the case of West Nile, though, a lab worker had previously been infected with a different, but closely related virus. Still, the earlier infection did not protect against West Nile infection, though it may have modified the severity of the worker's illness.
-- Lois Levitan, PhD Program Leader Environmental Risk Analysis Program Center for the Environment 213 Rice Hall, Cornell University Ithaca, New York USA 14853-5601 Phone: (607) 255-4765 Fax: (607) 255-0238 Email: LCL3@cornell.edu Program Email: envrisk@cornell.edu Web:http://www.cfe.cornell.edu/ERAP
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