Health Buzz: The Mysteries Stumping Swine Flu Experts and Other Health News
By Megan Johnson
Posted October 15, 2009
What Has Experts Stumped on Swine Flu?
Close to 400,000 cases of H1N1 infection have been confirmed by the World Health Organization, but flu experts still do not know exactly how the virus is spread, Reuters reports.
Mucus droplets contain flu virus that can live on surfaces and can be spread through close contact.
But there is a chance H1N1 could also get passed through feces, flu expert Tim Uyeki of the U.S. Centers for Disease Control and Prevention tells Reuters.
There are other big unanswered questions about H1N1, Reuters reports, including the number of people infected and how often the virus turns deadly.
Tests used to confirm infection are not very reliable, Reuters says, and are in short supply for the numbers of people infected.
As a result, the WHO and CDC can only estimate that the number of H1N1 cases far exceeds those confirmed. The agencies guess the true number of infections is in the millions, according to Reuters.
FACTBOX-New flu still raises questions among experts
Thu Oct 15, 2009 8:54am EDT
By Maggie Fox, Health and Science Editor
WASHINGTON, Oct 15 (Reuters) - How many people have been infected with the new swine flu? How many will it kill? How do you catch it?
Health authorities around the world are trying to persuade people to line up to be vaccinated against the pandemic H1N1 virus even as they struggle to answer these basic questions.
H1N1 swine flu was declared a pandemic in June and the World Health Organization says more than 375,000 people globally have been infected and 4,500 have died.
But these are just laboratory-confirmed cases and the WHO says they are the tip of the iceberg. Only a small fraction of people who get swine flu ever have it confirmed by a doctor.
Here is a rundown of what experts do and do not know about pandemic H1N1 influenza.
WHAT THEY KNOW
* The virus spread around the world in the space of six weeks and is now virtually everywhere.
* It strongly resembles seasonal influenza in that it causes fever, sore throat, a dry cough, muscle aches and tiredness.
* Unlike seasonal influenza, worst among the elderly, this new influenza batters younger people.
* Many people escape without symptoms. Dr. Tim Uyeki, a flu expert at the U.S. Centers for Disease Control and Prevention, says studies show 12 percent of people do not have fever. “A lot of people might think they don’t have influenza because they don’t have classic influenza-like illness,” Uyeki told a meeting of the Pan American Health Organization on Wednesday.
* H1N1 may cause symptoms not normally seen in seasonal flu. “We are seeing diarrhea and vomiting in children of all ages as well as adults,” Uyeki said. It can also infect the heart, a condition called myocarditis, affect the brain in what is called encephalopathy and cause multiple organ failure.
* The incubation period — the time from infection to when symptoms begin — ranges from one to four days.
* People can spread virus for 24 hours after the fever stops.
* Adults over the age of 60 are less likely to be infected and to become seriously ill with H1N1, in part because they seem to have some immunity to it. The highest rates of hospitalization are among the youngest children — aged up to 4 — but the highest rates of death are in adults aged 50 to 64.
* The new vaccine should protect against H1N1 well and antiviral drugs can treat it if given soon enough.
WHAT THEY DON’T KNOW
* How many people have been infected. The World Health Organization and CDC stopped counting months ago. There are not enough diagnostic tests in the world to test everyone who gets sick, and not enough doctors, nurses or technicians to administer them. The tests that exist are not very good at detecting H1N1. All WHO or CDC will say is that “millions” have been infected.
* The fatality rate for H1N1. Uyeki says death rate estimates are all under 1 percent with a median range of 0.4 percent. Without knowing how many people in total have been infected, researchers cannot say what proportion have died. Seasonal influenza kills less than 0.1 percent of patients but this adds up to 250,000 to 500,000 people globally each year.
* How people catch it. “We don’t actually have good data on understanding how this virus is transmitted,” Uyeki said. The virus lives in little droplets of mucus and tests show it can be picked up on surfaces such as computer keyboards, passed in a sneeze or during close conversation, and perhaps transmitted in smaller particles that can float up to six feet (2 metres).
Uyeki said it is possible H1N1 may be passed in feces, as the virus affects the gastrointestinal tract, but no one knows.
* How long patients are contagious. “I think we don’t really understand this well,” said Uyeki. People with higher fevers and children appear to “shed” more virus.
* What makes a flu virus deadly. Genetic analysis has shown nothing special about the viruses infecting people who died, said Dr. Michael Shaw, assistant director of laboratory science at CDC’s influenza division. “There is nothing that really stands out about these viruses that have been isolated from the severe or fatal cases,” Shaw told the PAHO meeting.
* What other viruses are out there. Shaw said farmers rarely test swine herds, a known source of new flu viruses.
“When you go and pull the data that’s available from GenBank you can find maybe 300 sequences from North American swine viruses,” Shaw said. “There is essentially nothing from Africa or Central or South America. There obviously are some gaps that need to be plugged so that something (else) like this doesn’t surprise us.”