Emerging infectious diseases
I was reading about the Infectious Diseases Society of America 2004 Annual Meeting and was particularly interested in the disclosures on the issue of Emerging and Re-emerging Infectious Diseases. I'm having flash-backs to my virology seminars, fungal morphology research, and molecular bio lectures and the hours in the lab running electrophoresis gels, the PCR machine and the electron microscopes.
What is really frightening to me about these emerging diseases, is how low-key things are in the media. Obviously, I know enough to be afraid, very afraid. Take the emerging fungal diseases! My god! David Warnock from the CDC noted "unprecedented changes in the pattern of serious fungal infections" during the past 20 years. Particularly impressive has been the emergence of species of Candida other than Candida albicans and Zygomycetes. For Candida species, Candida glabrata has become the second most common cause of Candida fungemia now accounting for 20% to 25% of cases in North America, while in Latin America, Candida parapsilosis is now second in frequency. This is frightening.
And then there is West Nile Virus! For 2004, the states with the largest number of cases were Arizona and California. The total number of cases reported through September 30, 2004 was 1784, substantially less than 2003 when there were over 9000 cases. The only state with no cases to date in the continental United States is Washington. Studies indicate that the virus can be contracted by birds who eat the dead, such as crows and blue jays, and it is certain to continue to be transmissible to humans. Whats so bad about WNV? It creates meningoencephalitis in humans, the worst cases of which cause acute flaccid paralysis. Fever, confusion, meningismus. Those who are paralyzed usually require tracheotomy, 3 out of 4 never recover motor funtion, and 3 out of 4 died within 30 days of the onset of symptoms. It appears that there are 2 current therapeutic trials (hyperimmune globulin and interferon) showing promise in treatment, so long as people are diagnosed early enough.
Norovirus seems to be emerging as well. It appears there was an outbreak of norovirus in a 103-bed VA nursing home in Pennsylvania. The investigation indicated that 42 patients (42% of residents) and 10 of 60 (17%) employees had norovirus gastroenteritis. It appears to have originaled with a resident who had a visit from a spouse with gastroenteritis. They got the outbreak under control with serious effort, managing to contain it. Cruise ships, on the other hand, are quite another story. There have been outbreaks of norovirus gastroenteritis with the involvement of 2278 of 27,168 total passengers on 12 cruise ships, yielding a rate of symptomatic infection of 8.3%. It is estimated that there is a high-rate of asymptomatic carriers (estimated at 30%), which makes control/containment very difficult. Of particular note is that the virus is transmissable person-to-person. It may be foodborne and waterborne, and persists on surfaces for as long as a week!
Bird Flu: Influenza is responsible for 250,000-500,000 deaths per year, including an average of 36,000 deaths last year in the United States. The obvious concern with Bird Flu is the potential for a new strain, such as this one, to cause an explosive epidemic similar to 1918-1919 Swine Flu outbreak which is estimated to have had over 500 million infections and 20-40 million deaths, primarily in persons aged 20-40 years. Between WWI and the Swine Flu, the US and Europe almost lost an entire generation (I wrote a paper on this for a virology seminar, the conclusion was that we are over-due for an outbreak if this intensity). Against this historical background of human influenza cases involving human strains, we now have the newly introduced avian strain, influenza A (H5N1). This organism is now epidemic in poultry and wild birds in much of Asia. H5N1 has been transmitted from poultry to humans: at the time of the meeting, there had been a total of 42 cases in humans with 30 deaths. Supposedly there was person-to-person transmission of H5N1 reported in Thailand, however, this form of transmission is still considered highly inefficient. Lets hope it remains so...the mortality rate is too damned high. There appears to be a vaccine in development, though how they are going to vaccinate the hundreds of millions of birds in Asia, I have no idea.
What the common person calls "Mad Cow Disease" in humans, but the medical profession calls Variant Creutzfeldt-Jakob disease was included in the literature review for the conference. Apparently, there is evidence of transmission by blood transfusion of the prion protein (PrP) in England. It is time for the US Food and Drug Administration to look at transfusion practices. How are we going to screen blood for prions? They are smaller than viruses.
Conclusion... stay away from birds, Asia, VA nursing homes, blood transfusions, cruise ships, angry cows, and fungi ;)
What is really frightening to me about these emerging diseases, is how low-key things are in the media. Obviously, I know enough to be afraid, very afraid. Take the emerging fungal diseases! My god! David Warnock from the CDC noted "unprecedented changes in the pattern of serious fungal infections" during the past 20 years. Particularly impressive has been the emergence of species of Candida other than Candida albicans and Zygomycetes. For Candida species, Candida glabrata has become the second most common cause of Candida fungemia now accounting for 20% to 25% of cases in North America, while in Latin America, Candida parapsilosis is now second in frequency. This is frightening.
And then there is West Nile Virus! For 2004, the states with the largest number of cases were Arizona and California. The total number of cases reported through September 30, 2004 was 1784, substantially less than 2003 when there were over 9000 cases. The only state with no cases to date in the continental United States is Washington. Studies indicate that the virus can be contracted by birds who eat the dead, such as crows and blue jays, and it is certain to continue to be transmissible to humans. Whats so bad about WNV? It creates meningoencephalitis in humans, the worst cases of which cause acute flaccid paralysis. Fever, confusion, meningismus. Those who are paralyzed usually require tracheotomy, 3 out of 4 never recover motor funtion, and 3 out of 4 died within 30 days of the onset of symptoms. It appears that there are 2 current therapeutic trials (hyperimmune globulin and interferon) showing promise in treatment, so long as people are diagnosed early enough.
Norovirus seems to be emerging as well. It appears there was an outbreak of norovirus in a 103-bed VA nursing home in Pennsylvania. The investigation indicated that 42 patients (42% of residents) and 10 of 60 (17%) employees had norovirus gastroenteritis. It appears to have originaled with a resident who had a visit from a spouse with gastroenteritis. They got the outbreak under control with serious effort, managing to contain it. Cruise ships, on the other hand, are quite another story. There have been outbreaks of norovirus gastroenteritis with the involvement of 2278 of 27,168 total passengers on 12 cruise ships, yielding a rate of symptomatic infection of 8.3%. It is estimated that there is a high-rate of asymptomatic carriers (estimated at 30%), which makes control/containment very difficult. Of particular note is that the virus is transmissable person-to-person. It may be foodborne and waterborne, and persists on surfaces for as long as a week!
Bird Flu: Influenza is responsible for 250,000-500,000 deaths per year, including an average of 36,000 deaths last year in the United States. The obvious concern with Bird Flu is the potential for a new strain, such as this one, to cause an explosive epidemic similar to 1918-1919 Swine Flu outbreak which is estimated to have had over 500 million infections and 20-40 million deaths, primarily in persons aged 20-40 years. Between WWI and the Swine Flu, the US and Europe almost lost an entire generation (I wrote a paper on this for a virology seminar, the conclusion was that we are over-due for an outbreak if this intensity). Against this historical background of human influenza cases involving human strains, we now have the newly introduced avian strain, influenza A (H5N1). This organism is now epidemic in poultry and wild birds in much of Asia. H5N1 has been transmitted from poultry to humans: at the time of the meeting, there had been a total of 42 cases in humans with 30 deaths. Supposedly there was person-to-person transmission of H5N1 reported in Thailand, however, this form of transmission is still considered highly inefficient. Lets hope it remains so...the mortality rate is too damned high. There appears to be a vaccine in development, though how they are going to vaccinate the hundreds of millions of birds in Asia, I have no idea.
What the common person calls "Mad Cow Disease" in humans, but the medical profession calls Variant Creutzfeldt-Jakob disease was included in the literature review for the conference. Apparently, there is evidence of transmission by blood transfusion of the prion protein (PrP) in England. It is time for the US Food and Drug Administration to look at transfusion practices. How are we going to screen blood for prions? They are smaller than viruses.
Conclusion... stay away from birds, Asia, VA nursing homes, blood transfusions, cruise ships, angry cows, and fungi ;)
posted by KR | 3/03/2005 09:59:00 PM
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