Worried parents kept children at home in New York on Wednesday out of the fear that they might catch A(H1N1) influenza, commonly known as swine flu, after the virus had forced officials to close schools.
The Centres for Disease Control and Prevention said on Wednesday the number of deaths from the swine flu in the US has risen to eight with 5,710 confirmed and probable cases throughout the country.
The World Health Organisation in Geneva reported 10,243 cases around the globe, including 80 deaths.
The New York City government had closed nine schools by on Wednesday after new cases were confirmed. But other schools, most of them in the Queens borough, closed because of the high absenteeism as parents kept children at home, bringing the total of schools closed to 26, local news reports said.
So far there has been one swine flu-related death in New York, which has a population of more than eight million. Late Sunday a vice principal at a Queens school, Mitchell Wiener, died of confirmed H1N1 flu.
An 18-month-old who died on Monday had been suspected of having the swine flu, but city health officials said on Wednesday preliminary tests for the virus were negative. A final result would still take several days.
There are about 200 confirmed cases of swine flu, all of them in schools in Queens. New York has about 1.2 million school students and more than 500 private and public schools.
Health authorities said there has been a dramatic increase in the number of doctor visits, in pediatric as well as for illnesses affecting adults.
Mayor Michael Bloomberg said at a daily news conference that a large number of children were seeking medical assistance for symptoms, most of which were not related to swine flu at all.
"It's very a difficult situation for parents, who also have work responsibilities as well," Bloomberg said.
The fear of swine flu has compelled New York's United Federation of Teachers to set up telephone hotlines in all five boroughs to collect information related to the flu outbreaks in schools.
Repeatedly, Bloomberg and City Hall officials have advised residents who develop flu symptoms to remain at home and seek medical assistance if severely ill.
Health commissioner Thomas Frieden said H1N1 continues to spread in the city, but the proportion of people severely ill has not increased. However, he did not rule out the possibility that there could be severely ill people in coming days.
The swine flu situation in New York is aggravated by the fact that doctors and hospitals do not have laboratory capability yet to test for H1N1. Only the city's health department or the Centres for Diseases Control in Atlanta can confirm an H1N1 case.
About 70 percent of those hospitalised with the virus in the US have underlying medical conditions, such as pregnancy, lung problems or heart disease, the CDC said on Wednesday.
A CDC study released earlier this week of hospitalised patients in California found that obesity was also a risk factor for the flu strain along with lung disease, immuno-suppression, chronic cardiac disease and diabetes.