Can You Get Swine Flu More Than Once?

We have been hearing several reports from people in Mexico in particular saying that they thought they were infected again, but they had not been tested so no one new for sure. Dr. Niman over at Recombinomics had this to say back on 10 October. I never posted it because there was no other confirmation, but I remembered it because it made some sense and was interesting. I am only posting a few paragraphs.

http://www.recombinomics.com/News/10100901/H1N1_Infection_Titer.html

The recently released data on the clinical trial in Australia suggests that such re-infections may be linked to low titers generated during mild infections. Although prior pandemic H1N1 infections were among exclusion criteria, 31% of enrollees had titers of 40 or more at baseline. Since there is little cross reactivity between contemporary seasonal H1N1 and pandemic swine H1N1, the baseline titers are almost certainly due to pandemic H1N1 infections that were not disclosed or not know the enrollee. Since many who are infected experience mild disease, including infections without fever, it is likely that many or most of these enrollees had mild infections.

Figure two suggests that although these enrollees had prior antibodies, the titers were relatively low (the vast majority were between 40 and 160) and most had significant improvements (increases of 4 fold or more) after a single injection, suggesting the weak responses to earlier natural infections would provide limited immunological protection, which would support common re-infections.

These data would also explain the limited level of drift, because naïve hosts as well as those with prior mild infections would be susceptible to re-infections, which would limit the selective pressure offered by genetic drift. Indeed, in recent CDC weekly updates, only one isolate has shown reduced titers to the pandemic vaccine target. However, this recently identified isolate may signal the start or accelerated drift as more of the target population develop higher antibody levels.

CDC confirms Kanawha County pediatrician had swine flu -- twice

http://www.dailymail.com/News/Kanawha/200911230838

Parsons says she's spoken with CDC representatives about the results, and they said the double infection isn't all that unbelievable.

"They said this happens every year with seasonal flu, so there's no reason to expect that it wouldn't happen with swine flu," Parsons said. "Every flu strain can change a little bit."

The pediatrician says there may have been a tiny change in the virus that stopped her immune system from recognizing it or her body never built up immunity to it.

(hat tip pfi/monotreme)

Vaccination was not the topic.

Dr. Henry Niman remarks on the positive confirmation of H1N1 re-infections noted in the first post of this thread. His theory on how this occurs, and what it could mean for future cases is unproven but interesting nonetheless. I hope that he is not correct, but that remains to be seen. The prediction of a third wave is probably right on target, however.

The mutation he mentions is also of interest. There has been quite a bit of speculation about what it could mean, but there is no agreement on its significance. It is now being reported in many countries just in the past week, maybe because they are now actively looking for it.

...the H1N1 virus was evolving slowly, reflecting an ease of infection of a naïve population. The jump from swine H1N1 into humans allows for infections with low doses of virus. Low concentration of virus produces a mild infection and a weak antibody response. The rapid spread creates widespread antibody, but the low level allows for re-infection from individuals with a higher viral load. A higher viral load can be created in a school environment, where some students could be infected multiple times because of frequent contact with infected students.

Thus, the increased viral load could overcome the weak immune-response and re-infect those infected earlier, leading to a second wave. However, the higher viral load leads to more serious infections, especially for those not infected in the first wave. Consequently more previously health young adults develop more serious symptoms, leading to an increase in hospitalizations and deaths. The higher viral load, especially when combined with receptor binding domain changes such as D225G can lead to the type of cases seen in Ukraine, where a high percentage of young adults develop infections that destroy both lungs in a matter of a few days.

In many areas, including Ukraine, this wave is subsiding, but the holiday season will lead to new infections by viruses with regional markers, leading to a third wave in early 2010.

Full comments at: http://www.recombinomics.com/News/11250901/H1N1_X2.html

South Korea Reports First Suspected A/H1N1 Re-infection Case

http://ow.ly/164ui2

Health officials said the baby was admitted to a hospital in the southeastern city of Gimhae in September due to high fever, and was confirmed to be infected with the virus by Green Cross Reference Laboratory that tests samples provided by local clinics and hospitals. The baby later recovered after receiving antiviral treatment.

However, the baby was sent to hospital again on Nov. 20 as she had a temperature reaching 39.1 C and showed respiratory-related symptoms, and later was tested positive for the A/H1N1 strain, the officials said.

Samples taken from the baby will be sent to the Korea Centers for Disease Control and Prevention to check its genetic sequence to find out whether it is a mutated strain of the new flu, the officials added.

(hat tip flutrackers/Dutchy)

Ok, so does this mean if you've had a mild case, then if you are reinfected, would you be LESS ill because you've had it before? Or would you be MORE ill? Hmmm.....

More importantly, you would, imo be less likely to have a fatal case because you would have at least some protective antibodies. It still sounds like the baby was sick enough though she has survived, and the pediatrician in the first link as well.

Personally, I would rather boost antibody via vaccine rather than get sick twice. The flu is no picnic. I hate getting sick.