Symptom patterns differ between pandemic, seasonal flu in Singapore

May 24, 2010

In a tropical environment, influenza A(H1N1) appeared milder than seasonal flu, was less likely to cause fever and upset stomach and more likely to infect younger individuals, according to a report in the May 24 issue of Archives of Internal Medicine.

Tropical climates may be least optimal for the survival of the influenza virus, according to background information in the article. In Singapore, the temperature ranges from 73 degrees to 95 degrees Fahrenheit and the humidity from 48 percent to 100 percent throughout the year. The incidence of influenza peaks in June through July and November through January in Singapore, although cases can be detected throughout the year.

In 2009, a new rapid detection method was designed to detect from the new influenza A(H1N1) virus and was used during a period of enhanced surveillance for influenza after global pandemic alerts were announced. Julian Wei-Tze Tang, Ph.D., M.R.C.P., M.R.C.Path., of National University Hospital, Singapore, and colleagues analyzed trends and symptoms among patients in Singapore during this period, from May to July 2009.

During the 12-week surveillance period, 2,683 individuals with symptoms, close contacts or travelers were tested using the rapid-detection assay. Of these, 742 (27.6 percent) were positive for any type of , including 547 cases (20.4 percent) of influenza A(H1N1).

Early cases appeared slightly milder than seasonal flu and had a different symptom pattern. The most common symptoms among individuals with pandemic influenza were cough (88.1 percent), fever (79.3 percent), sore throat (53.7 percent) and runny nose (49.9 percent). Individuals with the predominant strain of seasonal influenza most commonly had fever (88 percent), cough (81.4 percent), runny nose (55.7 percent) and sore throat (38.3 percent).

Seasonal influenza affected individuals of all ages, with a higher proportion of those 5 years and younger, while the pandemic virus was more likely to affect children and young adults and had very few elderly cases.

"It is likely that these symptom patterns will continue to evolve and change as the novel pandemic influenza A(H1N1/2009) eventually predominates, globally, in the susceptible human population," the authors conclude. "However, this early window period in this first wave of the pandemic has provided an opportunity to compare the symptomatology of these different viruses in this particular tropical environment and ethnically diverse population during this transitional period."

Explore further: Controlling Ebola in West Africa most effective way to decrease international risk

More information: Arch Intern Med. 2010;170[10]:861-867.

add to favorites email to friend print save as pdf

Related Stories

H1N1 influenza hits older children

May 04, 2010

Children hospitalized with pandemic H1N1 influenza in 2009 were older and more likely to have underlying medical conditions than children hospitalized with seasonal influenza during prior flu seasons, according to a study ...

Of swine, birds and men -- pandemic H1N1 flu

Feb 01, 2010

Current research suggests that pandemic H1N1 influenza of swine origin has distinct means of transmission from the seasonal flu, yet does not result in the pathogenic severity of avian flu viruses. The related report by ...

Influenza in Africa should not be ignored

Dec 15, 2009

Influenza is circulating in Africa, but virtually no information or attention is evident, says a new essay in this week's PLoS Medicine. Maria Yazdanbakhsh and Peter Kremsner argue that the lack of adequate surveillance means ...

Google Flu Trends estimates off

May 17, 2010

Google Flu Trends is not as accurate at estimating rates of laboratory-confirmed influenza as CDC national surveillance programs, according to a new study from the University of Washington.

Recommended for you

WHO: Ebola vaccine trials in W. Africa in January

3 hours ago

Tens of thousands of doses of experimental Ebola vaccines could be available for "real-world" testing in West Africa as soon as January as long as they are deemed safe, a top World Health Organization official ...

Ebola cases rise sharply in western Sierra Leone

4 hours ago

After emerging months ago in eastern Sierra Leone, Ebola is now hitting the western edges of the country where the capital is located with dozens of people falling sick each day, the government said Tuesday. So many people ...

User comments : 0