Presentation on theme: "Who Is At Risk Of Exposure To The Novel H1N1 Influenza Virus? Tanya D. Graham, DVM, Diplomate ACVP South Dakota State University Animal Disease Research."— Presentation transcript:
Who Is At Risk Of Exposure To The Novel H1N1 Influenza Virus? Tanya D. Graham, DVM, Diplomate ACVP South Dakota State University Animal Disease Research & Diagnostic Laboratory
Pandemics Come In Waves Pandemic viruses enter the population over multiple time periods/seasons. Once people think the illness rates are subsiding they stop paying attention to social distancing, hand washing, and cough etiquette. Leads to new waves of influenza throughout the community. Stay informed. CDC website is excellent source of information.
Is The Pandemic H1N1 Really All That Bad? No immunity to this new (novel) virus Proportion of people infected will be much higher than typical seasonal flu A virus that is fatal in “only” 0.15% of cases but infects twice the typical number of people will cause ~3 times more deaths (~100K) than seasonal flu will. Lipstitch M, et al. Managing and Reducing Uncertainty in an Emerging Influenza Pandemic. N Engl J Med 361(2):112-115. July 9, 2009.
Isn’t This Just More Media Hype? 1918 influenza pandemic infected > 25% of the world population Estimated 50-100 million humans died 2009 H1N1 pandemic currently not anymore severe than regular seasonal flu
Underlying Disease Present In At Least Half Of The Fatal Cases
Who Is At Risk? Pigs, turkeys, and presumably other species are at risk of catching the novel H1N1 influenza virus from an infected human/other animals. People are risk of catching the novel H1N1 influenza virus from other people with one exception: ▫ Groups with occupational risk of exposure to an infected swine herd DVM Personnel working at swine facilities / hobby farmers State / federal employees involved in disease control efforts
What Is The Worse Case Scenario With This Pandemic H1N1 Strain? 40% of the U.S. population could catch the novel H1N1 in next two years Several hundred thousand could die w/o vaccine Will Asian H5N1 (Bird Flu) virus swap genes with the novel H1N1 and start yet another pandemic? ▫ The mortality rate of bird flu is ~60% (six times worse than the 1918 pandemic virus)
Modes Of Transmission For ALL Human Influenza Viruses http://www.youtube.com/watch?v=qKiQA5e-fPg Davidhazy, 2007
2 Main Routes Of Infection: Inhalation & Transfer Inhalation of infectious droplets spread by sneezing, coughing, talking, breathing Direct transfer of respiratory secretions to another person (coughing, sneezing, talking at close distances (ballistic droplets) Indirect transfer by contaminated hands (light switch, door knob) Virus can survive 5 to 15 min on hands; 24 to 48 hrs on inanimate surfaces
Short Range vs. Long Range & Infectious Droplets Initial epidemiologists thought close contact was required for transmission ▫ Based on studies demonstrating that spacing beds in barracks or field hospitals or desks in schools > 3 ft apart reduced transmission rate. Glover, 1920; Feigin, 1982.
Short Range vs. Long Range & Infectious Droplets Recent evidence indicates transmission may occur at distances of more than 3 ft Xie, 2007; Wannamaker, 1954; Aintablian, 1998; Wong, 2004; Scales, 2003 CDC has recently expanded definition of “short range” to < 2 meters (~6.5 ft) CDC definition of “long range” > 2 meters
However!!!! No empirical evidence that increasing the recommended distance for control measures to two meters (6.5 feet) will result in lower influenza attack rates. No experimental data exists that would “measure” the risk of infections at a variety of distances from an infected person. This is why it is so important to stay at home when you are sick with the flu.
Minimizing The Risk Of Infection Regular hand washing Good respiratory hygiene (aka “Cough Etiquette”) Cover mouth/nose when coughing or sneezing Use tissue/sleeve/arm rather than hand Wear a mask (esp. if you are the sick one) Encourage co-workers / employees / friends & family to stay home when they are sick Stay home until you are fever free for at least 24 hours Avoid crowded places / large gatherings Social distancing No single action protects completely
CDC’s Recent Recommendations Concerning Face Masks “There may be times during a pandemic when you must be in a crowded setting or in close contact with people who might be ill. During such times, the use of a facemask or a respirator might help prevent the spread of pandemic flu.”
However!!!! No Scientific Studies Have Determined If Face Masks Are Protective “The range of large droplets that fall to the ground is generally no more than 3 feet.” No scientific data to support this statement Arose from a quote by Chapin-1910/repeated in literature Research in 1890s found Talking sprayed viable bacteria ~20 ft Whispering sprayed bacteria ~24 ft Combination of coughing, speaking, and sneezing carried bacteria 40 ft
Should I Wear A Mask? Surgical masks ▫ Protect others from contaminants generated by the wearer ▫ Do not protect wearer against inhalation of hazardous material
Should I Wear A Mask? N95 & N100 Respirators—shield the wearer from inhalational hazards ▫ Made of polypropylene wool felt, or fiberglass paper ▫ Particles become enmeshed within fibers
Should I Wear A Mask? To properly wear a respirator professional fit testing is required ▫ Administer saccharin / banana oil / Bitrex ▫ The presence of taste, irritation, or smell = didn’t seal properly N95 / other respirators do not work if you have facial hair ▫ Cannot get an effective “seal” between the facial skin and edge of the mask
These Are Not Your Parent’s Mucous Membranes Mucous membranes line all organ systems that communicate with air Eye Nose Mouth Vagina Urethra Anus Important to wash your hands both before & after using restroom
Current Diagnostic Tests Are Not Very Sensitive Current tests capable of detecting novel A (H1N1) virus from respiratory specimens have a low sensitivity (40%-69%) Thus a positive result is useful but a negative result does not rule out infection with novel H1N1 influenza virus http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5830a2.htm
What Are Antiviral Drugs “Antiviral drugs are prescription medicines (pills, liquid or an inhaled powder) that fight against the flu by keeping flu viruses from reproducing in your body. If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. Antivirals may be prioritized for persons with severe illness or those at higher risk for flu complications.” http://www.cdc.gov/h1n1flu/vaccination/public/vaccination_qa_pub.htm
Antivirals & Drug Resistance During the early stages of a pandemic ▫ Strain specific vaccines are not available ▫ Antiviral drugs are used to decrease mortality and help prevent the spread of infection Drug resistance can occur in some people
Are Antivirals Useful In Children? Study involving 1766 children ▫ Effects of the neuraminidase inhibitors Tamiflu® and Relenza® in children with seasonal influenza and ▫ Prevention of transmission to children in households. Conclusions ▫ Neuraminidase inhibitors provide a small benefit by shortening the duration of illness in children with seasonal influenza and reducing household transmission. ▫ Little effect on asthma exacerbations or the use of antibiotics Shun-Shin M et al. Neuraminidase inhibitors for treatment and prophylaxis of influenza in children: systematic review and meta-analysis of randomised controlled trials. BMJ 2009;339:b3172 August 10, 2009.
What’s The Deal With Tamiflu & Teenagers? >50 individuals taking Tamiflu in Japan have died People acted erratically after taking Tamiflu ▫ There is growing concern among doctors and parents in Japan over the drug's possible side effects on children/teens FDA reviewed 103 cases involving Tamiflu ▫ 95% of the cases came from Japan ▫ Japan—24.5 million prescriptions (2001 ) ▫ US—6.5 million prescriptions
What’s The Deal With Tamiflu & Teenagers? FDA required Roche (makers of Tamiflu) to put a caution on the label—look out for strange behavior. ▫ Updated in March of 2008 to indicate that some cases were fatal (suicides). Not all cases of nervous system disorder will be caused by the use of antivirals. ▫ Delirium disorders associated with influenza occur in about 4 of every 100,000 flu patients in US without the use of any drugs.
Should I Or My Family Receive Antiviral Treatment? Vaccinations? Talk with your physician to determine what course of treatment is best for you & your child ▫ Consider having this conversation during school- mandated physicals or other appointments with your doctor before flu season strikes Monitor the CDC website for new information about the novel H1N1 pandemic virus Always ask questions!
When Will A Vaccine Be Available? The seasonal flu vaccine will not provide protection against the novel H1N1 pandemic strain A vaccine for the novel H1N1 strain is being produced now-may be available around Thanksgiving Both seasonal flu & novel H1N1 vaccines can be given at the same time, in different anatomic locations. All persons currently recommended for seasonal influenza vaccine, including those aged ≥65 years, should receive the seasonal vaccine as soon as it is available. There are no changes in the recommendations for pneumococcal vaccines (i.e. if you are in the target group you should still get the pneumococcal vaccination too)
CDC Expects Initial Vaccine Shortage* This Group Will Receive Vaccine First Not in particular order Pregnant women People who live with/care for children < 6 month old Health care / emergency medical services personnel Children 6 months to 4-year-olds Children 5 to 18-year-olds w/ chronic medical conditions Followed by Vaccination of everyone 25 to 64 years old Followed by Vaccination of 65+ years old
So If I Catch It, How Long Do I Have To Stay At Home? Rule for most people: “CDC recommends that people with influenza-like illness remain at home until at least 24 hours after they are free of fever (100° F)…without the use of fever-reducing medications.”
If I Survive Am I Immune? If you become sick and survive infection with the circulating pandemic strain of virus you can treat the sick without worry of becoming ill again (as long as the virus has not significantly evolved into a new strain). State and local public health departments should be able to determine the nature of the strains circulating locally and regionally through their surveillance activities. If you did not become sick in a previous wave you may still be susceptible during subsequent waves. Regardless, it is always best to use basic infection control precautions.